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Manufacturing of Polymer-Matrix Composites
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Manufacturing of Polymer-Matrix Composites

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Composites and Nanocomposites".

Deadline for manuscript submissions: closed (5 August 2024) | Viewed by 28039

Special Issue Editors

Prof. Dr. Thomas Neumeyer

E-Mail Website
Guest Editor
Leibniz Institute for Composite Materials (IVW), University of Kaiserslautern-Landau (RPTU), 67663 Kaiserslautern, Germany
Interests: processing of polymer composites; fiber reinforced composites; polymer foams; lightweight materials; injection molding; additive manufacturing; sustainability
Prof. Dr. Volker Altstädt

E-Mail Website
Guest Editor
Department of Polymer Engineering, University of Bayreuth, 95444 Bayreuth, Germany
Interests: environmentally friendly polymers; lightweight materials; functional polymers; advanced processing & testing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polymer–matrix composites play a central role in the energy transition with their low density. Wind rotor blades, pressure tanks for hydrogen, battery housings—none of these applications can operate without those materials. Lightweight materials combined with a high degree of functional integration offer many opportunities to reduce moving masses and thus significantly contribute to resource efficiency and sustainability. The properties of the composite parts can be tailored based on the type of reinforcement and the selected processing technique.

In the future, processing methods for polymer–matrix composites must not only be economical but also use a minimum of energy and resources. Furthermore, aspects of circular economy and the use of secondary materials with varying properties must be taken into account. Sustainability assessments must play a central role in process development. Additionally, it is important to meet the growing trend towards individualization of products without reducing productivity.

In this Special Issue, new approaches with respect to the processing of polymer composites will be presented and discussed. The aim is to understand the interactions between process, structure of the reinforcement, and resulting properties. Special attention will be given to sustainable approaches with a focus on circular economy and energy-efficient processing. Adaptive and customizable technologies will also be part of this issue.

Contributions focused on the manufacturing of polymer–matrix composites in any of the following topics are of particular interest:

  • Novel processing approaches for thermosets as well as for thermoplastic polymer composites;
  • Fibers and textiles;
  • Additive manufacturing technologies for polymer composites;
  • Resource-efficient processing technologies for polymer–matrix composites;
  • Joining technologies for polymer composites;
  • Process monitoring, modeling, and control.

Prof. Dr. Thomas Neumeyer
Prof. Dr. Volker Altstädt
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • polymer–matrix composites
  • composite processing
  • filament winding
  • pultrusion
  • resin transfer molding
  • prepreg technologies
  • tape placement
  • injection overmolding
  • additive manufacturing
  • resource-efficient processing

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Published Papers (11 papers)

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Research

17 pages, 13381 KiB  
Article
Vacuum Chamber Infusion for Fiber-Reinforced Composites
by Benjamin Grisin, Stefan Carosella and Peter Middendorf
Polymers 2024, 16(19), 2763; https://doi.org/10.3390/polym16192763 - 30 Sep 2024
Viewed by 1053
Abstract
A new approach to an automatable fiber impregnation and consolidation process for the manufacturing of fiber-reinforced composite parts is presented in this article. Therefore, a vacuum chamber sealing machine classically used in food packaging is modified for this approach—Vacuum Chamber Infusion (VCI). Dry [...] Read more.
A new approach to an automatable fiber impregnation and consolidation process for the manufacturing of fiber-reinforced composite parts is presented in this article. Therefore, a vacuum chamber sealing machine classically used in food packaging is modified for this approach—Vacuum Chamber Infusion (VCI). Dry fiber placement (DFP) preforms, made from 30 k carbon fiber tape, with different layer amounts and fiber orientations, are infused with the VCI and with the state-of-the-art process—Vacuum Assisted Process (VAP)—as the reference. VCI uses a closed system that is evacuated once, while VAP uses a permanently evacuated open system. Since process management greatly influences material properties, the mechanical properties, void content, and fiber volume fraction (FVF) are analyzed. In addition, the study aims to identify how the complexity of a resin infusion process can be reduced, the automation potential can be increased, and the number of consumables can be reduced. Comparable material characteristics and a reduction in consumables, setup complexity, and manufacturing time by a factor of four could be approved for VCI. A void content of less than 2% is measured for both processes and an FVF of 39% for VCI and 45% for VAP is achieved. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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Figure 1

Figure 1
<p>VAP infusion setup and principle.</p> Full article ">Figure 2
<p>Modified Vacuum chamber machine for resin infusion, modifications are highlighted.</p> Full article ">Figure 3
<p>Scheme of the vacuum chamber infusion process. 1–4: Infusion with the inner bag. 5 and 6: Consolidation of the impregnated preform with an outer bag and 2 consolidation plates.</p> Full article ">Figure 4
<p>The geometry of sample plates. A, B, and C: areas for void content and fiber volume fraction. Grey area: area for tensile and bending specimens.</p> Full article ">Figure 5
<p>Representative cross-sections of the unidirectional configurations. Magnification: 250×, (<b>a</b>) VCI_UD_1 sample area B, (<b>b</b>) VCI_UD_2 sample area A, (<b>c</b>) VCI_UD_3 sample area A, (<b>d</b>) VAP_UD_1 sample area C, (<b>e</b>) VAP_UD_2 sample area B, (<b>f</b>) VAP_UD_2 sample area B.</p> Full article ">Figure 5 Cont.
<p>Representative cross-sections of the unidirectional configurations. Magnification: 250×, (<b>a</b>) VCI_UD_1 sample area B, (<b>b</b>) VCI_UD_2 sample area A, (<b>c</b>) VCI_UD_3 sample area A, (<b>d</b>) VAP_UD_1 sample area C, (<b>e</b>) VAP_UD_2 sample area B, (<b>f</b>) VAP_UD_2 sample area B.</p> Full article ">Figure 6
<p>Representative cross-section with voids of the unidirectional configuration VCI. Magnification: 500×.</p> Full article ">Figure 7
<p>Representative cross-sections of the 0/90° configuration magnification 250×, (<b>a</b>) VCI_0_90_1 sample area A, (<b>b</b>) VCI_0_90_2 sample area B, (<b>c</b>) VCI_0_90_3 sample area A, (<b>d</b>) VAP_0_90_1 sample area A, (<b>e</b>) VAP_0_90_2 sample area C, (<b>f</b>) VAP_0_90_3 sample area B.</p> Full article ">Figure 7 Cont.
<p>Representative cross-sections of the 0/90° configuration magnification 250×, (<b>a</b>) VCI_0_90_1 sample area A, (<b>b</b>) VCI_0_90_2 sample area B, (<b>c</b>) VCI_0_90_3 sample area A, (<b>d</b>) VAP_0_90_1 sample area A, (<b>e</b>) VAP_0_90_2 sample area C, (<b>f</b>) VAP_0_90_3 sample area B.</p> Full article ">
27 pages, 6668 KiB  
Article
Multi-Objectives Optimization of Plastic Injection Molding Process Parameters Based on Numerical DNN-GA-MCS Strategy
by Feng Guo, Dosuck Han and Naksoo Kim
Polymers 2024, 16(16), 2247; https://doi.org/10.3390/polym16162247 - 7 Aug 2024
Viewed by 1606
Abstract
An intelligent optimization technique has been presented to enhance the multiple structural performance of PA6-20CF carbon fiber-reinforced polymer (CFRP) plastic injection molding (PIM) products. This approach integrates a deep neural network (DNN), Non-dominated Sorting Genetic Algorithm II (NSGA-II), and Monte Carlo simulation (MCS), [...] Read more.
An intelligent optimization technique has been presented to enhance the multiple structural performance of PA6-20CF carbon fiber-reinforced polymer (CFRP) plastic injection molding (PIM) products. This approach integrates a deep neural network (DNN), Non-dominated Sorting Genetic Algorithm II (NSGA-II), and Monte Carlo simulation (MCS), collectively referred to as the DNN-GA-MCS strategy. The main objective is to ascertain complex process parameters while elucidating the intrinsic relationships between processing methods and material properties. To realize this, a numerical study on the PIM structural performance of an automotive front engine hood panel was conducted, considering fiber orientation tensor (FOT), warpage, and equivalent plastic strain (PEEQ). The mold temperature, melt temperature, packing pressure, packing time, injection time, cooling temperature, and cooling time were employed as design variables. Subsequently, multiple objective optimizations of the molding process parameters were employed by GA. The utilization of Z-score normalization metrics provided a robust framework for evaluating the comprehensive objective function. The numerical target response in PIM is extremely intricate, but the stability offered by the DNN-GA-MCS strategy ensures precision for accurate results. The enhancement effect of global and local multi-objectives on the molded polymer–metal hybrid (PMH) front hood panel was verified, and the numerical results showed that this strategy can quickly and accurately select the optimal process parameter settings. Compared with the training set mean value, the objectives were increased by 8.63%, 6.61%, and 9.75%, respectively. Compared to the full AA 5083 hood panel scenario, our design reduces weight by 16.67%, and achievements of 92.54%, 93.75%, and 106.85% were obtained in lateral, longitudinal, and torsional strain energy, respectively. In summary, our proposed methodology demonstrates considerable potential in improving the, highlighting its significant impact on the optimization of structural performance. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
►▼ Show Figures

Figure 1

Figure 1
<p>Numerical simulations implementation process of mapping operation flow in the Helius module for advanced material exchange.</p> Full article ">Figure 2
<p>(<b>a</b>) PA6-20CF specimen samples manufactured by PIM, (<b>b</b>) schematic diagram of specimen samples with various fiber directions (<span class="html-italic">θ</span>) from the PIM samples (X as loading axis), (<b>c</b>) fiber arrangement and fiber orientation tensor (<span class="html-italic">θ</span>) in the sample of 0°, 45°, and 90°, (<b>d</b>) dimensions of ASTM-D 638-02a-IV type sample and slicing positions of tensile specimens from the plate. Reproduced from [<a href="#B5-polymers-16-02247" class="html-bibr">5</a>], MDPI, 2023.</p> Full article ">Figure 3
<p>Numerical and experimental curves of PA6-20CF ASTM-D638 tensile specimens. Reproduced from [<a href="#B5-polymers-16-02247" class="html-bibr">5</a>], MDPI, 2023.</p> Full article ">Figure 4
<p>Tensile engineering stress–engineering strain curves of PA6-20CF ASTM-D638 tensile specimens of fiber orientation tensor (<span class="html-italic">θ</span>) as (<b>a</b>) 0°, (<b>b</b>) 45°, and (<b>c</b>) 90°. Reproduced from [<a href="#B5-polymers-16-02247" class="html-bibr">5</a>], MDPI, 2023.</p> Full article ">Figure 5
<p>Schematic diagram of assembly FEA model with car front hood panel, main parts’ measured dimensions, and injection molding process parameter LHD sampling scheme.</p> Full article ">Figure 6
<p>The boundary conditions used for evaluation are (<b>a</b>) lateral stiffness, (<b>b</b>) transversal stiffness, and (<b>c</b>) torsional stiffness.</p> Full article ">Figure 7
<p>Definition of objective functions for evaluation in an example case of (<b>a</b>) fiber orientation tensor, (<b>b</b>) warpage, and (<b>c</b>) equivalent plastic strain (PEEQ).</p> Full article ">Figure 8
<p>Schematic diagram of injection molding process parameter optimization process.</p> Full article ">Figure 9
<p>(<b>a</b>) Schematic diagram of injection molding process parameter DNN structure modeling and (<b>b</b>) K-fold cross-validation array. We used K-fold cross-validation to ensure database consistency before training and prevent overfitting. In the K-fold cross-validation process, the dataset is divided into k groups and then trained or validated according to predetermined distribution standards.</p> Full article ">Figure 10
<p>The DNN validation results revealed a close correlation between predicted values and true values, as well as the relationship between approximation error and R-squared. Sub-figures show the training dataset (<b>a</b>–<b>c</b>) for FOT, warpage, and PEEQ and the test dataset (<b>d</b>–<b>f</b>) for FOT, warpage, and PEEQ. In these sub-figures, the circles represent the predicted mean of the DNN model, the error bars represent the standard deviation proving the reliability of the DNN model predictions, and the bar distribution represents the identification of collected data falling inside the range, demonstrating the setting reliability of the DNN model.</p> Full article ">Figure 11
<p>Schematic diagram of NSGA-II workflow.</p> Full article ">Figure 12
<p>Workflow of Monte Carlo simulation.</p> Full article ">Figure 13
<p>Approximate RSM model for the melt temperature, mold temperature, packing pressure, and cooling time variables with structural performances, depicting the response relationship across FOT, warpage, and PEEQ. (<b>a</b>)–(<b>i</b>) Distinct variables for each structural performance. Each sub-figure shows a unique relationship, describing the diversifications within DNN models under deliberation.</p> Full article ">Figure 14
<p>The Pareto optimal set contains multiple optimal responses with (<b>a</b>) 3D view design space section, (<b>b</b>) front-view section, (<b>c</b>) top-view section, and (<b>d</b>) side-view section.</p> Full article ">Figure 15
<p>Pareto chart of types of the frequencies for various molding process parameters of multi-objectives of (<b>a</b>) fiber orientation tensor (FOT), (<b>b</b>) warpage, and (<b>c</b>) equivalent plastic strain (PEEQ).</p> Full article ">Figure 16
<p>Comparison of PA6-20CF PMH and AA 5083 material case numerical optimization results of equivalent plastic strain (PEEQ) distribution with three boundary conditions of (<b>a</b>) lateral, (<b>b</b>) transverse, and (<b>c</b>) torsion.</p> Full article ">Figure 17
<p>After-mapping local stiffness results of the multi-boundary conditions for (<b>a</b>) lateral, (<b>b</b>) transverse, and (<b>c</b>) torsion.</p> Full article ">Figure 18
<p>Numerical optimization results of PA6-20CF PMH case and AA 5083 case of (<b>a</b>) comparison of strain energy values under lateral, transverse, and torsional conditions and (<b>b</b>) comparison of total strain energy value and weight value.</p> Full article ">
23 pages, 14159 KiB  
Article
A Study of Deployable Structures Based on Nature Inspired Curved-Crease Folding
by Gaurab Sundar Dutta, Dieter Meiners and Gerhard Ziegmann
Polymers 2024, 16(6), 766; https://doi.org/10.3390/polym16060766 - 11 Mar 2024
Cited by 2 | Viewed by 1703
Abstract
Fascinating 3D shapes arise when a thin planar sheet is folded without stretching, tearing or cutting. The elegance amplifies when the fold/crease is changed from a straight line to a curve, due to the association of plastic deformation via folding and elastic deformation [...] Read more.
Fascinating 3D shapes arise when a thin planar sheet is folded without stretching, tearing or cutting. The elegance amplifies when the fold/crease is changed from a straight line to a curve, due to the association of plastic deformation via folding and elastic deformation via bending. This results in the curved crease working as a hinge support providing deployability to the surface which is of significant interest in industrial engineering and architectural design. Consequently, finding a stable form of curved crease becomes pivotal in the development of deployable structures. This work proposes a novel way to evaluate such curves by taking inspiration from biomimicry. For this purpose, growth mechanism in plants was observed and an analogous model was developed to create a discrete curve of fold. A parametric model was developed for digital construction of the folded models. Test cases were formulated to compare the behavior of different folded models under various loading conditions. A simplified way to visualize the obtained results is proposed using visual programming tools. The models were further translated into physical prototypes with the aid of 3D printing, hybrid and cured-composite systems, where different mechanisms were adopted to achieve the folds. The prototypes were further tested under constrained boundary and compressive loading conditions, with results validating the analytical model. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
►▼ Show Figures

Figure 1

Figure 1
<p>Three basic straight-crease Origami examples: (<b>a</b>) Yoshimura/diamond pattern, (<b>b</b>) diagonal pattern and (<b>c</b>) Miura Ori/Herringbone pattern [<a href="#B3-polymers-16-00766" class="html-bibr">3</a>].</p> Full article ">Figure 2
<p>Comparison between straight-crease and curved-crease folding.</p> Full article ">Figure 3
<p>(<b>a</b>) Josef Albert with his students at paper folding course [<a href="#B5-polymers-16-00766" class="html-bibr">5</a>], (<b>b</b>) Josef Albert with one of the early curved-crease folded models comprising back-and-forth concentric circular folds [<a href="#B6-polymers-16-00766" class="html-bibr">6</a>], (<b>c</b>) a Bauhaus design model with definitions of mountains and valleys [<a href="#B7-polymers-16-00766" class="html-bibr">7</a>] (Pictures reproduced with permission).</p> Full article ">Figure 4
<p>(<b>a</b>) Irene Schawinsky’s concentric circle model, (<b>b</b>) Thoki Yenn’s “Before the Big Bang” model, (<b>c</b>) Kunihiko Kasahara’s model of “Extreme Origami” [<a href="#B8-polymers-16-00766" class="html-bibr">8</a>] (Pictures reproduced with permission).</p> Full article ">Figure 5
<p>(<b>a</b>) One of the celebrated works of David Huffman “Column with Cusps” reconstructed by Duks Koschitz [<a href="#B10-polymers-16-00766" class="html-bibr">10</a>], (<b>b</b>) computer-simulated image, (<b>c</b>) physical model of Ron Resch’s developable surface model named “The White Space Curve Fold with 3-fold Symmetry” [<a href="#B11-polymers-16-00766" class="html-bibr">11</a>] (Pictures reproduced with permission).</p> Full article ">Figure 6
<p>A few examples of curved-crease folded forms as use cases: (<b>a</b>) Prototype of a façade shading lamella based on ‘Flectofin’ design inspired from the deformation in the Strelitzia reginae flower [<a href="#B21-polymers-16-00766" class="html-bibr">21</a>], (<b>b</b>) a curved-crease origami face shield computer model [<a href="#B25-polymers-16-00766" class="html-bibr">25</a>], (<b>c</b>) ‘Bentley Tailor Made’ project by designer Kyungeun Ko in collaboration with RoboFold [<a href="#B26-polymers-16-00766" class="html-bibr">26</a>], (<b>d</b>) ‘Sit’—a stackable stool made of plywood designed by Andreas Lund [<a href="#B27-polymers-16-00766" class="html-bibr">27</a>], (<b>e</b>) the ‘Colonna Curva’ installation by Marco Hemmerling and Alessio Mazzucchi [<a href="#B28-polymers-16-00766" class="html-bibr">28</a>] (Pictures reproduced with permission).</p> Full article ">Figure 7
<p>A few examples of folded deployable forms in fiber-reinforced composites: (<b>a</b>) Layup schematics of a foldable composite where the fold along the hinge is obtained by having two rigid traditionally cured carbon fiber-reinforced facets squeezing a dry layer of fiberglass impregnated with a very flexible epoxy resin system [<a href="#B29-polymers-16-00766" class="html-bibr">29</a>], (<b>b</b>) a woven fiber deployable antenna reflector demonstrator in deployed configurations [<a href="#B30-polymers-16-00766" class="html-bibr">30</a>], (<b>c</b>) an architecturally stiffened composite made up of dry fiber fabric and prepreg [<a href="#B31-polymers-16-00766" class="html-bibr">31</a>] (Pictures reproduced with permission).</p> Full article ">Figure 8
<p>Mirror reflection pattern evolving curved folding.</p> Full article ">Figure 9
<p>Illustration of initial case-study setup with offset definition.</p> Full article ">Figure 10
<p>Parametric modeling of folding in Grasshopper with Kingkong toolboxes.</p> Full article ">Figure 11
<p>Step-by-step development of folded models based on a line and curved crease.</p> Full article ">Figure 12
<p>Equally scaled deformation state of the models simulated using the Grasshopper Karamba plugin for self-weight with one edge being fixed and the representative design space definition <span class="html-italic">abcd</span> with a 3-point NURB curve as one potential curve of folding.</p> Full article ">Figure 13
<p>Schematic representation of a 2D form-finding process taking inspiration from nature by correlating a plant-growth algorithm with a representative growth intensity factor.</p> Full article ">Figure 14
<p>Step-by-step explanation of the process of evolving a curve by taking inspiration from a plant growth mechanism.</p> Full article ">Figure 15
<p>Equally scaled mesh deformation comparison between the original 3-pt NURB curved-crease model and the evolved curved-crease model with the corresponding deformation coefficient <span class="html-italic">ξ</span> for self-weight and user-regulated compressive load at a random point on the overhanging face of the shape.</p> Full article ">Figure 16
<p>Rough sketch of two valley fold test case setups with deformation results obtained via Grasshopper analysis.</p> Full article ">Figure 17
<p>Different methods adopted for prototype construction and validation.</p> Full article ">Figure 18
<p>Design process and 3D printed models using the functional crease channel.</p> Full article ">Figure 19
<p>Slot mechanism designs for multi-material samples and printed prototypes.</p> Full article ">Figure 20
<p>Design space definition <span class="html-italic">abcd</span>, material preparation and final hybrid composite samples for each crease definition for both minor and major offsets.</p> Full article ">Figure 21
<p>Illustration of two-stage impregnation process adopted for discrete curing of fibers.</p> Full article ">Figure 22
<p>Discrete resin infusion setup for a sample and the final cured samples with the fold region infused with thermoplastic resin.</p> Full article ">Figure 23
<p>Aggregated force-deformation distribution for samples produced by 3D printing using an ABS material comprising functional crease channels.</p> Full article ">Figure 24
<p>Deformation under loading in samples produced with PETG and TPU consisting of the flexible- and exposed-fold designs.</p> Full article ">Figure 25
<p>Deformation under loading in samples produced with PETG and TPU consisting of the overlapped-fold design.</p> Full article ">Figure 26
<p>Compression loading results for samples produced by cutting and joining pre-consolidated fiber sheets.</p> Full article ">Figure 27
<p>(<b>a</b>) Representative scaled-up deformation models obtained via Grasshopper analysis, (<b>b</b>) results obtained from compressive load testing of the major offset curved samples produced by hybrid assembly.</p> Full article ">Figure 28
<p>Force–deformation plot under compression loads for samples produced by discrete curing of thin ply unidirectional carbon fiber fabric.</p> Full article ">Figure 29
<p>Force–deformation plot under compression loads for samples produced by discrete curing of thick ply unidirectional carbon fiber fabric.</p> Full article ">Figure 30
<p>(<b>a</b>) Unfolded 2D surface with fold creases, (<b>b</b>) deformation due to loading at a point on the crease.</p> Full article ">
14 pages, 5763 KiB  
Article
Numerical Modelling of the Thermoforming Behaviour of Thermoplastic Honeycomb Composite Sandwich Laminates
by Varun Kumar Minupala, Matthias Zscheyge, Thomas Glaesser, Maik Feldmann and Holm Altenbach
Polymers 2024, 16(5), 594; https://doi.org/10.3390/polym16050594 - 21 Feb 2024
Viewed by 1424
Abstract
Lightweight component design is effectively achievable through sandwich structures; many past research studies in the aerospace and racing sectors (since the 1920s) have proven it. To extend their application into the automotive and other transport industries, manufacturing cycle times must be reduced. This [...] Read more.
Lightweight component design is effectively achievable through sandwich structures; many past research studies in the aerospace and racing sectors (since the 1920s) have proven it. To extend their application into the automotive and other transport industries, manufacturing cycle times must be reduced. This can be achieved by sandwich materials made of continuous fibre-reinforced thermoplastic (CFRTP) cover layers and thermoplastic honeycomb cores. To widen the application of flat thermoplastic-based sandwich panels into complex parts, a novel forming technology was developed by the Fraunhofer Institute of Microstructure of Materials and Systems (IMWS). Manufacturing defects like wrinkling and surface waviness should be minimised to achieve high reproducibility of the sandwich components. Studying different manufacturing parameters and their influence on the final part is complex and challenging to analyse through experiments, as it is time-consuming. Therefore, a finite element (FE) modelling approach is implemented to reduce such efforts. Initially, a thermoforming model is developed and validated with experimental results to check its reliability. Further, different simulations are performed to optimise the novel sandwich-forming process. In this study, a thermoplastic sandwich made of polypropylene (PP) honeycomb core and polypropylene glass fibre (PP/GF) cross-ply as cover layers was used, and its numerical model was executed in LS-DYNA software release R11.2.1. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
►▼ Show Figures

Figure 1

Figure 1
<p>Organosandwich (<b>a</b>) continuous production of honeycomb core and in-line lamination of cover layers, (<b>b</b>) schematic illustration of the novel manufacturing process of TSM [<a href="#B3-polymers-16-00594" class="html-bibr">3</a>,<a href="#B4-polymers-16-00594" class="html-bibr">4</a>].</p> Full article ">Figure 2
<p>FEA workflow of process simulation of thermoforming and part design.</p> Full article ">Figure 3
<p>Localised non-harmonic wrinkle mode of sandwich cover layers [<a href="#B9-polymers-16-00594" class="html-bibr">9</a>].</p> Full article ">Figure 4
<p>Thermo-mechanical tensile testing of PP at different temperature.</p> Full article ">Figure 5
<p>Calibrated material at different temperatures for (<b>a</b>) unfilled PP, (<b>b</b>) PP/GF cross-ply.</p> Full article ">Figure 6
<p>Thermo-physical material properties of core and cover layers: (<b>a</b>) temperature dependent thermal conductivity, (<b>b</b>) temperature specific heat capacity.</p> Full article ">Figure 7
<p>(<b>a</b>) Representative idealised sandwich honeycomb cell. (<b>b</b>) Initial thermal state of the sandwich after heating step in thermoforming process.</p> Full article ">Figure 8
<p>Simulation showing: (<b>a</b>) Thermoformed Organosandwich 3D−shell demonstrator, and (<b>b</b>) shear stresses in the bottom cover layer.</p> Full article ">Figure 9
<p>Simulation showing: (<b>a</b>) Thermoformed Organosandwich 3D-shell demonstrator, (<b>b</b>) shear stresses in the bottom cover layer.</p> Full article ">Figure 10
<p>Thermoformed Organosandwich 3D−shell demonstrator part showing wrinkles on bottom cover layer.</p> Full article ">Figure 11
<p>Compressive stresses inside the inner ply of bottom layer, indicating wrinkles [in MPa].</p> Full article ">Figure 12
<p>3D–shell demonstrator, (<b>a</b>) original design with uniform thickness, (<b>b</b>) modified design with reduced thickness [<a href="#B6-polymers-16-00594" class="html-bibr">6</a>].</p> Full article ">Figure 13
<p>Modified design results (<b>a</b>) compressive stresses in the UD-ply of bottom cover layer, (<b>b</b>) thermoformed part of modified design.</p> Full article ">
23 pages, 2297 KiB  
Article
Bringing Light into the Dark—Overview of Environmental Impacts of Carbon Fiber Production and Potential Levers for Reduction
by Tobias Manuel Prenzel, Andrea Hohmann, Tim Prescher, Kerstin Angerer, Daniel Wehner, Robert Ilg, Tjark von Reden, Klaus Drechsler and Stefan Albrecht
Polymers 2024, 16(1), 12; https://doi.org/10.3390/polym16010012 - 19 Dec 2023
Cited by 2 | Viewed by 7174
Abstract
Carbon fibers (CFs) are a crucial material for lightweight structures with advanced mechanical performance. However, there is still a paucity of detailed understanding regarding the environmental impacts of production. Previously, mostly singled-out scenarios for CF production have been assessed, often based on scarce [...] Read more.
Carbon fibers (CFs) are a crucial material for lightweight structures with advanced mechanical performance. However, there is still a paucity of detailed understanding regarding the environmental impacts of production. Previously, mostly singled-out scenarios for CF production have been assessed, often based on scarce transparent inventory data. To expand the current knowledge and create a robust database for future evaluation, a life cycle assessment (LCA) was carried out. To this end, a detailed industry-approved LCI is published, which also proved plausible against the literature. Subsequently, based on a global scenario representing the market averages for precursor and CF production, the most relevant contributors to climate change (EF3.1 climate change, total) and the depletion of fossil energy carriers (EF3.1 resource use, fossil) were identified. The energy consumption in CF manufacturing was found to be responsible for 59% of the climate change and 48% of the fossil resource use. To enable a differentiated discussion of manufacturing locations and process energy consumption, 24 distinct scenarios were assessed. The findings demonstrate the significant dependence of the results on the scenarios’ boundary conditions: climate change ranges from 13.0 to 34.1 kg CO2 eq./kg CF and resource use from 262.3 to 497.9 MJ/kg CF. Through the investigated scenarios, the relevant reduction potentials were identified. The presented results help close an existing data gap for high-quality, regionalized, and technology-specific LCA results for the production of CF. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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<p>Carbon fiber manufacturing process from acrylonitrile based on [<a href="#B50-polymers-16-00012" class="html-bibr">50</a>,<a href="#B52-polymers-16-00012" class="html-bibr">52</a>]; the process steps for the production of high tensile strength carbon fibers from PAN are highlighted in blue.</p> Full article ">Figure 2
<p>Schematic illustration of input and output flows of carbon fiber production from PAN and the required process steps considered in the scope of this paper; grey arrows: precursor and product, white arrows: auxiliaries and emissions, blue box: process steps.</p> Full article ">Figure 3
<p>Global carbon fiber production capacity (2022) in the most relevant countries and regions, based on [<a href="#B4-polymers-16-00012" class="html-bibr">4</a>].</p> Full article ">Figure 4
<p>Results for the initial life cycle impact assessment of CF production regarding climate change (<b>a</b>) and resource use (<b>b</b>); green: precursor, black: product, blue: auxiliaries and emissions.</p> Full article ">Figure 5
<p>Climate change, global for carbon fiber production scenarios, and respective reduction potentials: (<b>a</b>) GLO 1—energy from grid mix, technological state of the art (c.f. <a href="#polymers-16-00012-f004" class="html-fig">Figure 4</a>); (<b>b</b>) GLO 2—energy from renewables for PAN production and CF production, technological state of the art; (<b>c</b>) GLO 3—energy from renewables for PAN production and CF production, technological optimization; green: precursor, black: product, blue: auxiliaries and emissions.</p> Full article ">Figure 6
<p>Fossil resource use, global carbon fiber production scenarios, and respective reduction potentials: (<b>a</b>) GLO 1—energy from grid mix, technological state of the art (c.f. <a href="#polymers-16-00012-f004" class="html-fig">Figure 4</a>); (<b>b</b>) GLO 2—energy from renewables for PAN production and CF production, technological state of the art; (<b>c</b>) GLO 3—energy from renewables for PAN production and CF production, technological optimization; green: precursor, black: product, blue: auxiliaries and emissions.</p> Full article ">Figure 7
<p>Climate change impacts of regionalized scenarios for carbon fiber production with the respective reduction potentials through energy from renewables (scenarios xx 2) and energy from renewables combined with technologically optimized process (scenarios xx 3).</p> Full article ">Figure 8
<p>Fossil resource use impacts of regionalized scenarios for carbon fiber production with the respective reduction potentials through energy from renewables (scenarios xx 2) and energy from renewables combined with technologically optimized process (scenarios xx 3).</p> Full article ">
21 pages, 7921 KiB  
Article
New Approach for Processing Recycled Carbon Staple Fiber Yarns into Unidirectionally Reinforced Recycled Carbon Staple Fiber Tape
by Martin Detzel, Peter Mitschang and Ulf Breuer
Polymers 2023, 15(23), 4575; https://doi.org/10.3390/polym15234575 - 30 Nov 2023
Cited by 1 | Viewed by 2125
Abstract
This study describes a novel process in which staple fiber yarns made from recycled carbon fibers (rCFs) and polyamide 6 (PA6) fibers are further processed into semi-finished tape products in a modified impregnation and calendaring process. In this process, the staple fiber yarns [...] Read more.
This study describes a novel process in which staple fiber yarns made from recycled carbon fibers (rCFs) and polyamide 6 (PA6) fibers are further processed into semi-finished tape products in a modified impregnation and calendaring process. In this process, the staple fiber yarns are heated above the melting temperature of the polymer, impregnated, and stretched to staple fiber tapes (SF tapes) in the calendaring unit. SF tapes with different degrees of stretching and/or repasses were produced. The individual width and thickness were measured in line by a laser profile sensor. From these tapes, preforms were manually laid and processed into laminates in an autoclave. The important physical properties of the unidirectionally reinforced laminates made of the tapes were compared with organic sheets wound from staple fiber yarns. With increasing stretching, both the fiber orientation and mechanical properties improved compared to the organic sheets made from unstretched staple fiber yarns. An improvement in fiber orientation relative to the process direction from 66.3% to 91.9% (between ±10°) and 39.1% to 71.6% (between ±5°), respectively, was achieved for a two-stage stretched tape. The tensile and flexural moduli were increased by 15.2% and 14.5%, respectively. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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<p>(<b>a</b>) rCF yarn and (<b>b</b>) close-up of the yarn.</p> Full article ">Figure 2
<p>(<b>a</b>) Tape production line, highlighting the most important components; (<b>b</b>) schematic illustration of the calendaring process; (<b>c</b>) close-up of the consolidation rolls, and (<b>d</b>) schematic illustration of the measurement setup of the laser profile sensor.</p> Full article ">Figure 3
<p>(<b>a</b>) Tape-laid laminate, (<b>b</b>) wound laminate, (<b>c</b>) autoclave process, and (<b>d</b>) consolidated laminate.</p> Full article ">Figure 4
<p>Distribution of the titer.</p> Full article ">Figure 5
<p>DSC-thermogram of the PA6 staple fiber and the PA6 wrapping filament.</p> Full article ">Figure 6
<p>TGA-thermogram of the PA6 staple fiber and the PA6 wrapping filament.</p> Full article ">Figure 7
<p>Width and calculated thickness of the tape P5_1 after the first pass through the tape manufacturing line.</p> Full article ">Figure 8
<p>Width and calculated thickness of the tape P5_2 after the second pass through the tape manufacturing line.</p> Full article ">Figure 9
<p>(<b>a</b>) Micrograph of P5_1; (<b>b</b>) micrograph of P5_2.</p> Full article ">Figure 10
<p>rCF fiber volume content for the yarns, reference laminate, and tape-laid laminates. Error bars represent the standard errors of the mean.</p> Full article ">Figure 11
<p>Fiber orientation distribution for the reference laminate R and the P3_2 tape-laid laminate (front and back side).</p> Full article ">Figure 12
<p>Fiber content aligned between ±10° and ±5° to the process direction for the reference laminate and the tape-laid laminates. Error bars represent the standard errors of the mean.</p> Full article ">Figure 13
<p>Tensile properties of the reference laminate and the tape-laid laminates. Error bars represent the standard errors of the mean.</p> Full article ">Figure 14
<p>Flexural properties of the reference laminate and the tape-laid laminates. Error bars represent the standard errors of the mean.</p> Full article ">Figure 15
<p>DSC-thermogram of the reference laminate and P3_2 tape-laid laminate.</p> Full article ">Figure 16
<p>Scanning electron microscope images of the fractured surfaces from the samples of the reference laminate after the tensile test (<b>a</b>) and the flexural test (<b>b</b>), as well as the samples of laminate P3_2 after the tensile test (<b>c</b>) and the flexural test (<b>d</b>).</p> Full article ">
22 pages, 7449 KiB  
Article
Challenges in Manufacturing of Hemp Fiber-Reinforced Organo Sheets with a Recycled PLA Matrix
by Maximilian Salmins, Florian Gortner and Peter Mitschang
Polymers 2023, 15(22), 4357; https://doi.org/10.3390/polym15224357 - 8 Nov 2023
Viewed by 1709
Abstract
This study investigates the influence of a hot press process on the properties of hemp fiber-reinforced organo sheets. Plain-woven fabric made from hemp staple fiber yarns is used as textile reinforcement, together with a recycled poly-lactic acid (PLA) matrix. Process pressure and temperature [...] Read more.
This study investigates the influence of a hot press process on the properties of hemp fiber-reinforced organo sheets. Plain-woven fabric made from hemp staple fiber yarns is used as textile reinforcement, together with a recycled poly-lactic acid (PLA) matrix. Process pressure and temperature are considered with three factor levels for each parameter. The parameter influence is examined based on the B-factor model, which considers the temperature-dependent viscosity of the polymer, as well as the process pressure for the calculation of a dimensionless value. Increasing these parameters theoretically promotes improvements in impregnation. This study found that the considered recycled polymer only allows a narrow corridor to achieve adequate impregnation quality alongside optimal bending properties. Temperatures below 170 °C impede impregnation due to the high melt viscosity, while temperature increases to 185 °C show the first signs of thermal degradation, with reduced bending modulus and strength. A comparison with hemp fiber-reinforced virgin polypropylene, manufactured with identical process parameters, showed that this reduction can be mainly attributed to polymer degradation rather than reduction in fiber properties. The process pressure should be at least 1.5 MPa to allow for sufficient compaction of the textile stack, thus reducing theoretical pore volume content to a minimum. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic representation of the bast fiber structure, after [<a href="#B8-polymers-15-04357" class="html-bibr">8</a>,<a href="#B13-polymers-15-04357" class="html-bibr">13</a>].</p> Full article ">Figure 2
<p>Schematic of impregnation process, based on [<a href="#B51-polymers-15-04357" class="html-bibr">51</a>] after [<a href="#B49-polymers-15-04357" class="html-bibr">49</a>,<a href="#B50-polymers-15-04357" class="html-bibr">50</a>].</p> Full article ">Figure 3
<p>Schematic of macro- and micro-impregnation, after [<a href="#B51-polymers-15-04357" class="html-bibr">51</a>].</p> Full article ">Figure 4
<p>Dry textile (<b>left</b>), recycled PLA powder (<b>middle</b>) and stack setup (<b>right</b>).</p> Full article ">Figure 5
<p>(<b>a</b>) Laboratory hot press with press tool; (<b>b</b>) setup for temperature measurement inside the fiber stack.</p> Full article ">Figure 6
<p>Comparison of temperature ramp and effective temperature alongside pressure ramp.</p> Full article ">Figure 7
<p>Correlation of process data with impregnation phases, with schematics based on [<a href="#B51-polymers-15-04357" class="html-bibr">51</a>] after [<a href="#B49-polymers-15-04357" class="html-bibr">49</a>,<a href="#B50-polymers-15-04357" class="html-bibr">50</a>].</p> Full article ">Figure 8
<p>(<b>a</b>) Points for organo sheet thickness measurements and (<b>b</b>) position of three point bending specimens within the organo sheet.</p> Full article ">Figure 9
<p>Setup for three point bending tests [<a href="#B57-polymers-15-04357" class="html-bibr">57</a>].</p> Full article ">Figure 10
<p>DSC curve recorded during differential scanning calorimetry.</p> Full article ">Figure 11
<p>Comparison of measured and predicted viscosity for the considered rPLA based on an Arrhenius equation.</p> Full article ">Figure 12
<p>Comparison of stack thicknesses for processes with a maximum temperature of 170 °C and different process pressures.</p> Full article ">Figure 13
<p>Influence of process pressure on the (<b>a</b>) timespan until the onset of macro-impregnation (MI); (<b>b</b>) stack temperature at the onset of macro-impregnation; (<b>c</b>) timespan for impregnation and (<b>d</b>) B-factor for each parameter combination.</p> Full article ">Figure 14
<p>Comparison of apparent impregnation qualities with their B-factor.</p> Full article ">Figure 15
<p>(<b>a</b>) Measured organo sheet thickness in comparison with target thickness; (<b>b</b>) polymer loss due to squeeze-out through the tool gap; (<b>c</b>) comparison of measured and theoretical organo sheet thickness based on its weight; (<b>d</b>) theoretical fiber and pore volume content based on organo sheet weight and thickness.</p> Full article ">Figure 16
<p>(<b>a</b>) Bending moduli and (<b>b</b>) bending strengths, compared to effective fiber volume content.</p> Full article ">Figure 17
<p>Effect of pore volume content on bending properties for a FVC of 37%.</p> Full article ">Figure 18
<p>(<b>a</b>) Bending modulus and (<b>b</b>) bending strengths compared to B-factors for each process.</p> Full article ">Figure 19
<p>Comparison of temperature influence in hemp–rPLA and hemp–PP organo sheets on (<b>a</b>) bending modulus and (<b>b</b>) bending strength.</p> Full article ">Figure 20
<p>Microsection of hemp–rPLA organo sheet.</p> Full article ">Figure A1
<p>DSC curve for polypropylene Borealis bj100hp with distinct recrystallization behavior during cooling, modified based on [<a href="#B51-polymers-15-04357" class="html-bibr">51</a>].</p> Full article ">
16 pages, 7191 KiB  
Article
Finite Element Simulation and Experimental Assessment of Laser Cutting Unidirectional CFRP at Cutting Angles of 45° and 90°
by Jan Keuntje, Selim Mrzljak, Lars Gerdes, Verena Wippo, Stefan Kaierle, Frank Walther and Peter Jaeschke
Polymers 2023, 15(18), 3851; https://doi.org/10.3390/polym15183851 - 21 Sep 2023
Cited by 1 | Viewed by 1427
Abstract
Laser cutting of carbon fibre-reinforced plastics (CFRP) is a promising alternative to traditional manufacturing methods due to its non-contact nature and high automation potential. To establish the process for an industrial application, it is necessary to predict the temperature fields arising as a [...] Read more.
Laser cutting of carbon fibre-reinforced plastics (CFRP) is a promising alternative to traditional manufacturing methods due to its non-contact nature and high automation potential. To establish the process for an industrial application, it is necessary to predict the temperature fields arising as a result of the laser energy input. Elevated temperatures during the cutting process can lead to damage in the composite’s matrix material, resulting in local changes in the structural properties and reduced material strength. To address this, a three-dimensional finite element model is developed to predict the temporal and spatial temperature evolution during laser cutting. Experimental values are compared with simulated temperatures, and the cutting kerf geometry is examined. Experiments are conducted at 45° and 90° cutting angles relative to the main fibre orientation using a 1.1 mm thick epoxy-based laminate. The simulation accurately captures the overall temperature field expansion caused by multiple laser beam passes over the workpiece. The influence of fibre orientation is evident, with deviations in specific temperature data indicating differences between the estimated and real material properties. The model tends to overestimate the ablation rate in the kerf geometry, attributed to mesh resolution limitations. Within the parameters investigated, hardly any expansion of a heat affected zone (HAZ) is visible, which is confirmed by the simulation results. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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<p>Schematic view of the experimental setup.</p> Full article ">Figure 2
<p>Different laser cutting simulation strategies: (<b>a</b>) summed up heat load applied at once and (<b>b</b>) adopted heat load applied step by step.</p> Full article ">Figure 3
<p>Finite element model: (<b>a</b>) larger scale and a (<b>b</b>) close-up of the cutting zone.</p> Full article ">Figure 4
<p>Thermographic imaging of the bottom side temperature field expansion over time: (<b>a</b>) at a 90° cutting angle and (<b>b</b>) at a 45° cutting angle.</p> Full article ">Figure 5
<p>Simulated temperature fields 500 ms after the fifth laser beam scan: (<b>a</b>) at a 90° cutting angle and (<b>b</b>) at a 45° cutting angle.</p> Full article ">Figure 6
<p>Comparison of the simulated and measured bottom surface temperature history in the centre of the kerf: (<b>a</b>) at a 90° cutting angle and (<b>b</b>) at a 45° cutting angle.</p> Full article ">Figure 7
<p>Comparison of the simulated and measured bottom surface temperature history at a 6 mm distance to the kerf: (<b>a</b>) at a 90° cutting angle and (<b>b</b>) at a 45° cutting angle.</p> Full article ">Figure 8
<p>(<b>a</b>) Cross sections after five scans at a 90° cutting angle and (<b>b</b>) close-up.</p> Full article ">Figure 9
<p>(<b>a</b>) Cross sections after five scans at a 45° cutting angle and (<b>b</b>) close-up.</p> Full article ">Figure 10
<p>Comparison between the simulated and real kerf geometry after five scans at a 90° cutting angle; red dashed lines indicate the original shape of the sample.</p> Full article ">Figure 11
<p>Simulated temperature plot on the cross section in the centre of the cut: (<b>a</b>) at a 45° cutting angle and (<b>b</b>) at a 90° cutting angle.</p> Full article ">
14 pages, 2376 KiB  
Article
Sustainable Pultruded Sandwich Profiles with Mycelium Core
by Marion Früchtl, Andreas Senz, Steffen Sydow, Jonas Benjamin Frank, Andrea Hohmann, Stefan Albrecht, Matthias Fischer, Maximilian Holland, Frederik Wilhelm and Henrik-Alexander Christ
Polymers 2023, 15(15), 3205; https://doi.org/10.3390/polym15153205 - 28 Jul 2023
Cited by 5 | Viewed by 1717
Abstract
This research focuses on exploring the potential of mycelium as a sustainable alternative to wood or solid foam in pultruded glass fiber-reinforced plastic (GFRP) sandwich profiles. The study evaluates the performance and the environmental sustainability potential of this composite by mechanical tests and [...] Read more.
This research focuses on exploring the potential of mycelium as a sustainable alternative to wood or solid foam in pultruded glass fiber-reinforced plastic (GFRP) sandwich profiles. The study evaluates the performance and the environmental sustainability potential of this composite by mechanical tests and life cycle assessment (LCA). Analysis and comparison of pultruded sandwich profiles with mycelium, polyurethane (PUR) foam and chipboard demonstrate that mycelium is competitive in terms of its performance and environmental impact. The LCA indicates that 88% of greenhouse gas emissions are attributed to mycelium production, with the heat pressing (laboratory scale) being the main culprit. When pultruded profiles with mycelium cores of densities 350 and 550 kg/m³ are produced using an oil-heated lab press, a global warming potential (GWP) of 5.74 and 9.10 kg CO2-eq. per functional unit was calculated, respectively. When using an electrically heated press, the GWP decreases to 1.50 and 1.78 kg CO2-eq. Compared to PUR foam, a reduction of 23% in GWP is possible. In order to leverage this potential, the material performance and the reproducibility of the properties must be further increased. Additionally, an adjustment of the manufacturing process with in situ mycelium deactivation during pultrusion could further reduce the energy consumption. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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<p>Mycelium cultivation and growth. (<b>a</b>) Inoculation of substrate using mycelium in growth bag; (<b>b</b>) growth of the material in a polypropylene (PP) growth box; (<b>c</b>) living mycelium after approximately 14 days of growth. (<b>d</b>) Zoom of the mature mycelium and the growth structure.</p> Full article ">Figure 2
<p>Manufacturing process (<b>a</b>) with reinforcing materials (glass fiber roving, glass fiber textiles and mycelium sandwich core) being impregnated with resin (<b>b</b>) and exiting the hot forming tool (<b>c</b>) at temperatures of up to 150 °C. The finished product is shown in full view (<b>d</b>).</p> Full article ">Figure 3
<p>Schematic drawing of the sandwich floor panel, not to scale.</p> Full article ">Figure 4
<p>Mycelium-glass fiber reinforced polymer (GFRP) sandwich composite in 4-point bending test.</p> Full article ">Figure 5
<p>Force-displacement diagram of the frontal pull test of the mycelium samples P1–P5.</p> Full article ">Figure 6
<p>Maximum deflection in the simulation model depending on the core material and the core thickness.</p> Full article ">Figure 7
<p>Maximum deflection in the simulation model compared to the total mass of the sandwich composite.</p> Full article ">Figure 8
<p>Percentage composition of the GWP for the production of the pultruded profile (dimensions 1000 × 120 × 10 mm³) with mycelium core ((<b>a</b>): density of 350 kg/m<sup>3</sup> and (<b>b</b>): density of 550 kg/m<sup>3</sup>).</p> Full article ">Figure 9
<p>Global warming potential (GWP) for the production of a pultruded profile (dimensions 1000 × 120 × 10 mm³). (<b>a</b>) In comparison, profile with mycelium core (density 350 kg/m<sup>3</sup> and component weight: 0.87 kg) taking into account various scenarios with PUR foam core (density 200 kg/m<sup>3</sup> and component weight: 0.64 kg). (<b>b</b>) Comparing profile with mycelium core (density 550 kg/m<sup>3</sup> and component weight 1.06 kg) considering various scenarios with chipboard core (density 650 kg/m<sup>3</sup> and component weight: 1.20 kg).</p> Full article ">
23 pages, 15313 KiB  
Article
A Study of Free-Form Shape Rationalization Using Biomimicry as Inspiration
by Gaurab Sundar Dutta, Dieter Meiners and Nina Merkert
Polymers 2023, 15(11), 2466; https://doi.org/10.3390/polym15112466 - 26 May 2023
Cited by 1 | Viewed by 2266
Abstract
Bridging the gap between the material and geometrical aspects of a structure is critical in lightweight construction. Throughout the history of structural development, shape rationalization has been of prime focus for designers and architects, with biological forms being a major source of inspiration. [...] Read more.
Bridging the gap between the material and geometrical aspects of a structure is critical in lightweight construction. Throughout the history of structural development, shape rationalization has been of prime focus for designers and architects, with biological forms being a major source of inspiration. In this work, an attempt is made to integrate different phases of design, construction, and fabrication under a single framework of parametric modeling with the help of visual programming. The idea is to offer a novel free-form shape rationalization process that can be realized with unidirectional materials. Taking inspiration from the growth of a plant, we established a relationship between form and force, which can be translated into different shapes using mathematical operators. Different prototypes of generated shapes were constructed using a combination of existing manufacturing processes to test the validity of the concept in both isotropic and anisotropic material domains. Moreover, for each material/manufacturing combination, generated geometrical shapes were compared with other equivalent and more conventional geometrical constructions, with compressive load-test results being the qualitative measure for each use case. Eventually, a 6-axis robot emulator was integrated with the setup, and corresponding adjustments were made such that a true free-form geometry could be visualized in a 3D space, thus closing the loop of digital fabrication. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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<p>(<b>a</b>) Hyperbolic Paraboloids in the interior of the Vaults of “La Sagrada Familía” constructed by Antoni Gaudí, Reprinted with permission from [<a href="#B12-polymers-15-02466" class="html-bibr">12</a>]; (<b>b</b>) Factory for Sicli SA, Geneva, Switzerland constructed by Heinz Isler [<a href="#B7-polymers-15-02466" class="html-bibr">7</a>]; (<b>c</b>) Market Hall, Argenteuil, 1967 an example of composite freeform structure created with geometric design approach [<a href="#B8-polymers-15-02466" class="html-bibr">8</a>]; (<b>d</b>) The full-scale prototype of the roof of the NEST HiLo unit 2017 [<a href="#B13-polymers-15-02466" class="html-bibr">13</a>]; (<b>e</b>) Dieste’s Gaussian vault under construction. The vault is subject to an ad hoc load test with a distributed load generated by the workforce [<a href="#B7-polymers-15-02466" class="html-bibr">7</a>].</p> Full article ">Figure 2
<p>Different phases of CD application in architecture [<a href="#B16-polymers-15-02466" class="html-bibr">16</a>,<a href="#B17-polymers-15-02466" class="html-bibr">17</a>].</p> Full article ">Figure 3
<p>Representative Grasshopper code for a basic parametric sphere with details of various components.</p> Full article ">Figure 4
<p>Schematic representation of 2D form-finding process following plant-growth algorithm with representative growth intensity factor for one such instance (in inset).</p> Full article ">Figure 5
<p>Illustration of 3D design space with evolved curves under different excitation forces with corresponding color codes.</p> Full article ">Figure 6
<p>Schematic representation of (<b>a</b>) translation surface and (<b>b</b>) surface of revolution generated from a curve.</p> Full article ">Figure 7
<p>Translation surfaces generated for the first case study.</p> Full article ">Figure 8
<p>Section of Karamba 3D FE programming.</p> Full article ">Figure 9
<p>Deformation coefficient <span class="html-italic">ξ</span> formulation and corresponding program code.</p> Full article ">Figure 10
<p>Deformation on grid meshes and corresponding ξ values.</p> Full article ">Figure 11
<p>Modified surface models.</p> Full article ">Figure 12
<p>3D-printed prototypes with attachments mimicking boundary conditions.</p> Full article ">Figure 13
<p>Setup and attachments to prepare and test hand-laminated fiber-grid surface samples.</p> Full article ">Figure 14
<p>Illustration of different steps involved in the mold-assisted VARI process.</p> Full article ">Figure 15
<p>Final cleaned and trimmed carbon fiber composite samples.</p> Full article ">Figure 16
<p>Schematic representation of the test setup.</p> Full article ">Figure 17
<p>Compressive load test results for 3D-printed surfaces with (<b>a</b>) two edges of translation being fixed, (<b>b</b>) all open boundaries being fixed.</p> Full article ">Figure 18
<p>(<b>a</b>) Compressive point load simulation on surface models in ABAQUS, (<b>b</b>) deformation coefficient ???? value comparison for random point load simulated in parametric solver.</p> Full article ">Figure 19
<p>Compressive load test results for hand-laminated fiber-grid surfaces with (<b>a</b>) two edges of translation being fixed, (<b>b</b>) all open boundaries being fixed.</p> Full article ">Figure 20
<p>Compressive load test results for fiber composite samples with two edges of translation being fixed.</p> Full article ">Figure 21
<p>Deformation illustration of different surfaces generated from basic curves along with their <span class="html-italic">ξ</span> values under different boundary and loading conditions.</p> Full article ">Figure 22
<p>Illustration of layer-by-layer slicing in conventional 3D printing slicer Ultimaker Cura [<a href="#B38-polymers-15-02466" class="html-bibr">38</a>] and loss of geometry definition. Here a geometry created from a 3D curvature (denotated by green curve on left) is reduced to 2D definition (denoted by printing path on right) due to printer limitation.</p> Full article ">Figure 23
<p>Two different slicing processes using Silkworm toolbox and corresponding G-code display in NC Viewer [<a href="#B39-polymers-15-02466" class="html-bibr">39</a>].</p> Full article ">Figure 24
<p>(<b>a</b>) Robot arm with attached marker, (<b>b</b>) manual controller.</p> Full article ">Figure 25
<p>Flowchart showing digital fabrication process.</p> Full article ">Figure 26
<p>2D shape visualization with (<b>a</b>) G-code information display in NC viewer and (<b>b</b>) curve drawn by a robot arm with same information as input.</p> Full article ">Figure 27
<p>3D shape visualization of four structural members of a system identifiable as 1,2,3 and 4 with (<b>a</b>) G-code information display in NC viewer and (<b>b</b>) corresponding start, mid, and end frames of robot arm movement for each corresponding curve.</p> Full article ">
24 pages, 7977 KiB  
Article
Approaching Polycarbonate as an LFT-D Material: Processing and Mechanical Properties
by Christoph Schelleis, Benedikt M. Scheuring, Wilfried V. Liebig, Andrew N. Hrymak and Frank Henning
Polymers 2023, 15(9), 2041; https://doi.org/10.3390/polym15092041 - 25 Apr 2023
Cited by 6 | Viewed by 2863
Abstract
Long-fiber thermoplastic (LFT) materials compounded via the direct LFT (LFT-D) process are very versatile composites in which polymers and continuous reinforcement fiber can be combined in almost any way. Polycarbonate (PC) as an amorphous thermoplastic matrix system reinforced with glass fibers (GFs) is [...] Read more.
Long-fiber thermoplastic (LFT) materials compounded via the direct LFT (LFT-D) process are very versatile composites in which polymers and continuous reinforcement fiber can be combined in almost any way. Polycarbonate (PC) as an amorphous thermoplastic matrix system reinforced with glass fibers (GFs) is a promising addition regarding the current development needs, for example battery enclosures for electromobility. Two approaches to the processing and compression molding of PC GF LFT-D materials with various parameter combinations of screw speed and fiber rovings are presented. The resulting fiber lengths averaged around 0.5 mm for all settings. The tensile, bending, Charpy, and impact properties were characterized and discussed in detail. Special attention to the characteristic charge and flow area formed by compression molding of LFT-D materials, as well as sample orientation was given. The tensile modulus was 10 GPa, while the strength surpassed 125 MPa. The flexural modulus can reach up to 11 GPa, and the flexural strength reached up to 216 MPa. PC GF LFT-D is a viable addition to the LFT-D process, exhibiting good mechanical properties and stable processability. Full article
(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)
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Figure 1
<p>Process scheme for compounding (<bold>left</bold>) and compression molding (<bold>right</bold>) of LFT-D materials.</p> Full article ">Figure 2
<p>Screw configuration of first TSE. This screw facilitates the plastification of polymer granulates. Extrusion direction from right to left indicated by the arrow.</p> Full article ">Figure 3
<p>Screw configuration of second TSE. This screw design featured one mixing element (GFM) and was considered a low-shear setup. Fiber reinforcement was incorporated into the molten matrix material over the course of the screw. Extrusion direction from right to left indicated by the arrow.</p> Full article ">Figure 4
<p>Relation of screw speed and continuous roving feed to resulting fiber mass fractions from 10% to 60% for a fixed polymer throughput of 30 kg/h in LFT-D.</p> Full article ">Figure 5
<p>Representation of the molding process with (<bold>a</bold>) polished steel mold with plastificate in charge position and (<bold>b</bold>) polished steel mold with molded plate and (<bold>c</bold>) schematic of the square plate mold with charge area, flow path, and resulting flow area. The position of the LFT-D plastificate is shown, including the extrusion direction. Possible orientations of the sampling are indicated.</p> Full article ">Figure 6
<p>Normalized fiber mass over all fiber mass fractions and processing parameters. Each diamond represents one sample.</p> Full article ">Figure 7
<p>Fiber length <inline-formula><mml:math id="mm85"><mml:semantics><mml:msub><mml:mi>l</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:semantics></mml:math></inline-formula> over all parameter sets resulting in PC GF40. Screw speed is shown increasing from left to right. Each diamond represents one sample.</p> Full article ">Figure 8
<p>Fiber property evaluation of 16 samples distributed evenly over one plate from V33. A histogram of <inline-formula><mml:math id="mm86"><mml:semantics><mml:msub><mml:mi>l</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:semantics></mml:math></inline-formula> over all fibers measured is depicted on the left. Red lines indicating the possible <inline-formula><mml:math id="mm87"><mml:semantics><mml:msub><mml:mi>l</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mi>r</mml:mi><mml:mi>i</mml:mi><mml:mi>t</mml:mi></mml:mrow></mml:msub></mml:semantics></mml:math></inline-formula>. Fiber mass fraction is shown on the upper right and fiber length <inline-formula><mml:math id="mm88"><mml:semantics><mml:msub><mml:mi>l</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:semantics></mml:math></inline-formula> on the lower right for all 16 positions. Darker colors indicate higher fiber mass fraction or fiber length respectively.</p> Full article ">Figure 9
<p>Parameter space of screw speed, roving amount, and resulting fiber mass fractions from 10% to 60%. Calculated SME left and measured fiber length <inline-formula><mml:math id="mm89"><mml:semantics><mml:msub><mml:mi>l</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:semantics></mml:math></inline-formula> right. Black dots indicate the various parameter sets. The parameter set V6 was used for all further characterizations.</p> Full article ">Figure 10
<p>Micrographs of PC GF LFT-D from (<bold>a</bold>) the charge and (<bold>b</bold>) the flow area with the marked shell core effect in the charge area.</p> Full article ">Figure 11
<p>SEM micrograph of a fracture surface of a 0° PC GF40 specimen out of the flow area after the tensile test. Fractured glass fibers are embedded in polymer matrix.</p> Full article ">Figure 12
<p>Polar plots of tensile modulus of elasticity (<bold>a</bold>) and tensile strength (<bold>b</bold>), each showing average properties in charge and flow area, respectively, with the associated scatter, in comparison with the results for pure PC taken from the data sheet.</p> Full article ">Figure 13
<p>Polar plot of the results from the four-point bending test separated into charge and flow area in (<bold>a</bold>) the flexural modulus of elasticity and (<bold>b</bold>) the flexural strength, in comparison with the results for pure PC from the three-point bending test taken from the data sheet.</p> Full article ">Figure 14
<p>Stress–strain curves of tensile tests with corresponding scatter range of all valid specimens in 0° and 90° orientations separated into charge (<bold>a</bold>) and flow area (<bold>b</bold>).</p> Full article ">Figure 15
<p>Schematic stress distribution and microstructure of specimens cut 90° to the flow direction. Schematically showing the shell and core zones in charge (<bold>left</bold>) and flow (<bold>right</bold>) area. Load cases for both bending (<bold>top</bold>) and tensile testing (<bold>bottom</bold>) are shown.</p> Full article ">Figure 16
<p>Representative puncture impact test curves of samples from charge and flow area. Average values, standard deviation of all tested samples, and the results for pure PC from the data sheet are shown in the table at the upper right edge of the figure.</p> Full article ">Figure 17
<p>Curves of impact force over displacement and corresponding fracture patterns from 5 J to 25 J. Flow orientation equals fiber orientation and can be found in the fracture pattern.</p> Full article ">Figure 18
<p>Charpy impact strength <inline-formula><mml:math id="mm90"><mml:semantics><mml:msub><mml:mi>α</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mi>U</mml:mi></mml:mrow></mml:msub></mml:semantics></mml:math></inline-formula> according to DIN EN ISO 179-1/1fU in a polar plot. Sampling in charge and flow area is shown separately.</p> Full article ">Figure 19
<p>DMA curves of storage modulus and tan <inline-formula><mml:math id="mm91"><mml:semantics><mml:mi>δ</mml:mi></mml:semantics></mml:math></inline-formula> of a 0° specimen taken from the flow area of GF40 PA6 and PC plates.</p> Full article ">Figure A1
<p>Further puncture impact test curves of five samples from charge (<bold>left</bold>) and flow (<bold>right</bold>) area.</p> Full article ">
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