CN107685497A - Smart laminated plate and preparation method with damage real-time perception and warning function - Google Patents

Abstract

The invention relates to an intelligent laminated board with real-time damage sensing and early warning functions and a preparation method thereof. The intelligent laminated board includes a fiber cloth layer, a piezoelectric ceramic unit and a resin sealing layer, and the piezoelectric ceramic unit is embedded in the fiber In the cloth layer, the resin sealing layer surrounds the fiber cloth layer, the wires of the piezoelectric ceramic unit extend outside the resin sealing layer, and the piezoelectric ceramic unit is embedded in the 1/2 thickness position of the fiber cloth layer . Compared with the prior art, the present invention can not only protect the piezoelectric sheet from being damaged, but also stimulate a signal with a high signal-to-noise ratio, and solve the problem that the adhesive piezoelectric sheet is easily detached from the structure under the actual on-line monitoring condition of the composite material structure. Sticky, fragile, and low signal-to-noise ratio of the excitation signal.

Description

Intelligent laminate with damage real-time perception and early warning function and preparation method

technical field

The invention relates to a composite material laminated board, in particular to an intelligent laminated board with damage real-time sensing and early warning functions and a preparation method thereof.

Background technique

Fiber-reinforced resin-based composite laminates have many characteristics such as high specific strength, specific modulus, and strong designability, and are favored by different engineering fields. However, the composite laminates used in practice are vulnerable to external dynamic and static effects and cause invisible damage to the naked eye. Guided waves have a series of advantages such as long transmission distance and high sensitivity. The damage real-time sensing and early warning technology based on guided waves can detect the damage in the laminate structure in time, so as to effectively avoid the catastrophic damage of the structure. In damage sensing and early warning technology systems using guided wave technology, transducers based on piezoelectric ceramic sheets are widely used to transmit or receive guided wave signals. In traditional methods, piezoceramic sheets are often glued to the surface of the structure by adhesives. However, under the action of load, the piezoelectric ceramic sheet is easy to debond from the structure and the signal cannot be collected, which affects the sensing and early warning functions. At the same time, the adhesive piezoelectric sheet cannot generate a guided wave signal with a high signal-to-noise ratio in the composite material structure, which affects the signal processing process and cannot realize real-time accurate perception and early warning of damage.

Contents of the invention

The purpose of the present invention is to provide an intelligent laminate with real-time damage sensing and early warning functions and a preparation method to overcome the defects in the above-mentioned prior art, which can not only protect the piezoelectric sheet from damage, but also stimulate a high signal-to-noise ratio Signal.

The purpose of the present invention can be achieved through the following technical solutions:

An intelligent laminated board with real-time damage sensing and early warning functions, comprising a fiber cloth layer, a piezoelectric ceramic unit and a resin sealing layer, the piezoelectric ceramic unit is embedded in the fiber cloth layer, and the resin sealing layer surrounds the The fiber cloth layer, the wires of the piezoelectric ceramic unit extend outside the resin sealing layer.

The piezoelectric ceramic unit is embedded in the 1/2 thickness position of the fiber cloth layer.

When the fiber cloth layer is an even-numbered layer structure, the piezoelectric ceramic unit is buried between the middle two layers;

When the fiber cloth layer has an odd-numbered layer structure, the piezoelectric ceramic unit is embedded in the middle layer.

The piezoelectric ceramic unit is a single piezoelectric sheet or an array of piezoelectric sheets.

The piezoelectric sheet is a circular piezoelectric ceramic wafer.

The raw materials of the resin sealing layer include epoxy resin, curing agent and accelerator, and the mass ratio of the epoxy resin, curing agent and accelerator is: 100:(0.1-1):(0.01-0.2).

A method for preparing an intelligent laminate with damage real-time perception and early warning functions, comprising the following steps:

Step 1: Lay the fiber cloth on the mold in a pre-designed laying form to form a fiber cloth layer, and at the same time place the piezoelectric ceramic unit with positive and negative wires in the fiber cloth layer to form a system;

Step 2: after laying the release cloth, the diversion net and the diversion pipe on the surface of the fiber cloth, the system is sealed with a vacuum bag combined with a sealant;

Step 3, uniformly stirring the epoxy resin, curing agent and accelerator to form a sealing liquid, using the pressure difference inside the system to pump the sealing liquid into the system, and curing to form a resin sealing layer;

Step 4, demoulding, to obtain an intelligent laminate with real-time damage sensing and early warning functions.

In the first step, the piezoelectric ceramic unit is embedded in the 1/2 thickness position of the fiber cloth layer.

In the third step, the mass ratio of the epoxy resin, curing agent and accelerator is: 100: (0.1-1): (0.01-0.2).

In the third step, the curing time is between 24h and 48h.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention embeds the piezoelectric ceramics in the fiber cloth layer, and under the premise of not destroying the structural strength of the composite material laminate, the piezoelectric ceramics are not easily affected by external loads to cause debonding and fragmentation, and the strength of the laminate is improved. Safety and reliability.

(2) The present invention utilizes the excellent processing technology of composite materials to integrate piezoelectric sheets (groups) into composite material laminates to form embedded-embedded waveguide excitation-receive signal laminate structures, which is different from existing Some paste-paste types have a higher signal-to-noise ratio, and their S0 amplitude is twice that of the latter.

(3) Utilizing the principle of probability imaging, the damage perception accuracy of the embedded-embedded guided wave excitation-receiving signal in the present invention is better than that of the adhesive-adhesive piezoelectric sheet group.

Description of drawings

Fig. 1 is a block diagram of the preparation method of an intelligent laminated board with real-time damage perception and early warning functions according to the present invention;

Fig. 2 is a schematic diagram of a piezoelectric sheet array used in the present invention;

Figure 3 shows the guided wave signal excitation and reception system and the four types of excitation-reception piezoelectric sheets used;

Figure 4 is a comparison of guided wave signals obtained by using different excitation-reception piezoelectric sheet forms;

Figure 5 is a comparison diagram of the positioning accuracy of different excitation-reception signals in the probability imaging algorithm, where (5a) is embedded-embedded, (5b) is embedded-pasted, and (5c) is pasted -embedding type, (5d) is paste-paste type.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

This embodiment provides an intelligent laminated board with real-time damage sensing and early warning functions, including a fiber cloth layer, a piezoelectric ceramic unit and a resin sealing layer, the piezoelectric ceramic unit is embedded in the fiber cloth layer, and the resin sealing layer surrounds the fiber cloth layer , the wires of the piezoceramic unit extend beyond the resin sealing layer. The smart laminate solves the problem of real-time damage detection and early warning technology for composite laminates. The piezoelectric ceramic sheet pasted on the surface of the laminate is susceptible to debonding and fragmentation due to external loads, and at the same time stimulates signal-to-noise comparison low problem.

The piezoelectric ceramic unit is embedded in the 1/2 thickness position of the fiber cloth layer, which increases the symmetrical wave amplitude and reduces the anti-symmetrical wave amplitude. The number and thickness of the fiber cloth layer are not limited. When the fiber cloth layer is an even-numbered layer structure, the piezoelectric ceramic unit is buried between the middle two layers; when the fiber cloth layer is an odd-numbered layer structure, the piezoelectric ceramic unit is buried in the middle. layer.

The piezoelectric ceramic unit is a single piezoelectric sheet or an array of piezoelectric sheets. The piezoelectric sheet is a circular piezoelectric ceramic wafer. In this embodiment, the number of layers and the thickness are not limited. The thickness is 1mm, the diameter is 10mm, and the center frequency is 210KHz.

The raw material of the resin sealing layer includes epoxy resin, curing agent and accelerator, the mass ratio of epoxy resin, curing agent and accelerator is: 100: (0.1～1): (0.01～0.2), curing agent and accelerator common commercially available materials. In this embodiment, the mass ratio of epoxy resin, curing agent and accelerator is: 100:0.5:0.1. The material cured with this ratio has good mechanical properties and moderate curing time.

The diameter of the positive and negative lead wires of the piezoelectric ceramic unit is 0.5mm, and the welding spot at the junction of the piezoelectric sheet and the lead wire is as small as possible, and it needs to be extended to 0.5m from the boundary of the laminate for connecting the guided wave monitoring equipment.

As shown in Figure 1, the preparation method of the above-mentioned intelligent laminated board with damage real-time perception and early warning function includes the following steps:

Step 1: Lay the fiber cloth on the mold according to the pre-designed laying form to form a fiber cloth layer, and at the same time embed the piezoelectric ceramic unit with positive and negative wires into the 1/2 thickness of the fiber cloth layer to form a system.

In this embodiment, the fiber cloth layer is provided with 4 layers of glass fiber cloth. First, two layers of glass fiber cloth 2 are laid on the glass plate mold 1 as a workbench, and then the piezoelectric ceramic sheet 3 is pasted on the surface of the glass fiber cloth with a universal glue, and then another two layers of glass fiber cloth are laid.

Step 2, sealing the piezoelectric ceramic sheet and the glass fiber cloth on the glass plate mold 1 by using the guide net, the release cloth and the vacuum bag 4 .

Step 3, use the resin storage tank 5, plastic conduit 6, resin collection tank 7 and vacuum pump 8 to connect the entire system in series; add the configured resin to the resin storage tank 5, turn on the vacuum pump 8 to slowly pump the resin into the system And seal and hold pressure, solidify, form the resin sealing layer. According to the temperature, the curing time is between 24h and 48h.

Step 4: After the resin is completely cured, the mold is demoulded to obtain a smart laminate with real-time damage sensing and early warning functions, and in-situ monitoring functions

As shown in Figure 2, in this embodiment, the piezoelectric ceramic unit adopts an array of piezoelectric sheets, and the embedded piezoelectric sheets are coded, numbered from PZT-0 to PZT-8, and the embedded piezoelectric sheets form a circular shape. Array, the distance from the central piezoelectric sheet is 200mm.

In conjunction with Fig. 3, using the guided wave excitation-reception system, the present invention compares the signals obtained by four different signal excitation-reception piezoelectric sheet groups; the four different excitation-reception piezoelectric sheet groups are respectively: (1) buried Embedded-embedded; (2) Embedded-pasted; (3) Pasted-embedded; (4) Pasted-pasted. The guided wave signals obtained by using four different forms of excitation-reception piezoelectric sheet groups are shown in Figure 4. Using four different excitation-receiving piezoelectric sheet groups, using the piezoelectric sheet array in Figure 2, combined with the probabilistic imaging algorithm, the damage location results of the laminate are shown in Figure 5. It can be seen that the signal obtained by using the embedded-embedded piezoelectric film array has a high signal-to-noise ratio, a high S0 amplitude, and good positioning accuracy, which proves the effectiveness of the present invention.

This implementation mode may also include:

1. The types of fibers in intelligent laminates with damage real-time sensing and early warning functions can be continuous fibers such as glass fibers, carbon fibers, and aramid fibers, and the diameter between fiber yarns should be smaller than the diameter of piezoelectric sheets;

2. The type of fiber in the intelligent laminate with damage real-time perception and early warning function can be unidirectional fiber or braided fiber, as long as the integrated piezoelectric film is located at 1/2 of the thickness of the laminate;

3. The resin in the intelligent laminate with damage real-time perception and early warning function can be epoxy resin, vinyl resin, etc., which can be cured at room temperature;

4. The composite material preparation process can be a vacuum-assisted resin injection process, or a laminate preparation process in which resin and fibers are pre-separated such as resin conversion molding (RTM).

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (10)

1. An intelligent laminated board with damage real-time perception and early warning functions, characterized in that it comprises a fiber cloth layer, a piezoelectric ceramic unit and a resin sealing layer, and the piezoelectric ceramic unit is embedded in the fiber cloth layer, and the The resin sealing layer surrounds the fiber cloth layer, and the wires of the piezoelectric ceramic unit extend outside the resin sealing layer. 2. The intelligent laminated board with damage real-time sensing and early warning functions according to claim 1, wherein the piezoelectric ceramic unit is embedded in the 1/2 thickness position of the fiber cloth layer. 3. The intelligent laminated board with damage real-time perception and early warning functions according to claim 2, characterized in that, when the fiber cloth layer is an even-numbered layer structure, the piezoelectric ceramic unit is embedded between the middle two layers; When the fiber cloth layer has an odd-numbered layer structure, the piezoelectric ceramic unit is embedded in the middle layer. 4. The intelligent laminated board with damage real-time sensing and early warning functions according to claim 1, wherein the piezoelectric ceramic unit is a single piezoelectric sheet or an array of piezoelectric sheets. 5. The intelligent laminated board with damage real-time sensing and early warning functions according to claim 4, wherein the piezoelectric sheet is a circular piezoelectric ceramic wafer. 6. The intelligent laminated board with damage real-time perception and early warning function according to claim 1, characterized in that, the material raw material of the resin sealing layer comprises epoxy resin, curing agent and accelerator, and the epoxy resin, The mass ratio of the curing agent and the accelerator is: 100: (0.1-1): (0.01-0.2). 7. A preparation method of an intelligent laminated board with damage real-time perception and early warning functions as claimed in claim 1, characterized in that, comprising the following steps: Step 1: Lay the fiber cloth on the mold in a pre-designed laying form to form a fiber cloth layer, and at the same time place the piezoelectric ceramic unit with positive and negative wires in the fiber cloth layer to form a system; Step 2: after laying the release cloth, the diversion net and the diversion pipe on the surface of the fiber cloth, the system is sealed with a vacuum bag combined with a sealant; Step 3, uniformly stirring the epoxy resin, curing agent and accelerator to form a sealing liquid, using the pressure difference inside the system to pump the sealing liquid into the system, and curing to form a resin sealing layer; Step 4, demoulding, to obtain an intelligent laminate with real-time damage sensing and early warning functions. 8 . The preparation method according to claim 7 , wherein, in the first step, the piezoelectric ceramic unit is embedded in a position of 1/2 thickness of the fiber cloth layer. 9. The preparation method according to claim 7, characterized in that in step 3, the mass ratio of the epoxy resin, curing agent and accelerator is: 100: (0.1～1): (0.01～0.2) . 10. The preparation method according to claim 7, characterized in that in the third step, the curing time is between 24h and 48h.