Testing System and Method for Dynamic Fracture Toughness of Biomimetic Composite Materials

Abstract

This invention discloses a testing system and method for the dynamic fracture toughness of biomimetic composite materials, belonging to the field of dynamic mechanics experiments. The testing system includes a velocity control system, a split Hopkinson bar device, and a biomimetic composite material test specimen. The split Hopkinson bar device includes a bullet, an incident rod, and a test fixture. The bullet and the incident rod have the same diameter, and the bullet, the incident rod, and the test fixture are all made of the same material. In use, the test specimen is placed on the test fixture and fixed by two clamps. The specimen is in contact with the bottom surface of the clamps. The wedge-shaped punch of the incident rod is in contact with the test specimen, and the punch is perpendicular to the span direction of the test specimen. A strain gauge is attached at 1 / 3 of the length of the incident rod. The bullet impacts the incident rod, and the strain gauge collects waveform data to complete the test. The dynamic fracture toughness of the test specimen is then calculated.

Description

Technical Field

[0001] This invention relates to a dynamic fracture toughness testing system for biomimetic composite materials, belonging to the field of dynamic mechanics experiments of materials. Background Technology

[0002] With the development of aerospace and transportation industries, higher demands are being placed on high-strength, lightweight materials. As a novel type of composite material, biomimetic composites mimic the microstructure of organisms in nature, achieving both lightweight properties and high toughness. Therefore, the microstructural characteristics of biomimetic materials can be utilized to develop lightweight, high-toughness composite materials. High-precision, rapid experimental testing systems can improve the efficiency of material testing and contribute to the improvement of material mechanical properties. The split Hopkinson bar is one of the main devices for testing the dynamic mechanical properties of materials, enabling the testing of mechanical property parameters under different strain rate conditions. Based on this, researchers Lu Fangyun et al. (Lu Fangyun, Chen Rong, Lin Yuliang, et al. Hopkinson Bar Experimental Techniques [M]. Beijing: Science Press, 2013) extended the Hopkinson bar experiment to a dynamic three-point bending experiment, which can experimentally test the fracture toughness of composite materials, thereby improving the fracture toughness of composite materials.

[0003] Biomimetic composite materials, such as shell-like structures, are composed of alternating layers of hard and soft materials. During dynamic three-point bend tests, an incident rod impacts the biomimetic composite sample. The location of the wedge-shaped impact point on the sample affects the test results. For the same sample, the impact velocity required to damage the sample is higher when impacting the soft material than when impacting the hard material. Therefore, to better control variables, the position of the test sample is adjusted using a fixture to ensure that each impact occurs at the location of the hard material.

[0004] In recent years, fracture mechanics has been widely applied in engineering fields. Under high strain rate conditions such as impact, dynamic fracture toughness is particularly important for evaluating the dynamic mechanical properties of biomimetic composite materials. Summary of the Invention

[0005] The present invention aims to provide a testing system and method for the dynamic fracture toughness of biomimetic composite materials, which can control the bullet firing speed and adjust the position of the biomimetic composite material test specimen.

[0006] This invention primarily utilizes the Hopkinson bar test to assess the dynamic fracture toughness of biomimetic composite material specimens. Precise measurement of the dynamic fracture performance of the biomimetic composite material is achieved by controlling the bullet's impact velocity. The test span and impact position of the incident rod are adjusted by moving the clamp position to ensure the impact location corresponds to the hard material within the biomimetic composite material. A quick-release valve releases air pressure from the cylinder, driving the bullet to impact the incident rod. After a dynamic load is applied to the incident rod, a wedge-shaped punch at its tip dynamically impacts the specimen. The load-displacement curve of the material is obtained by collecting incident and reflected wave signals from strain gauges on the incident rod, and the mechanical properties of the biomimetic composite material specimen are then calculated. This testing system considers both bullet velocity control and specimen position adjustment.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A testing system for the dynamic fracture toughness of biomimetic composite materials includes a speed control system, a split Hopkinson bar device, and a biomimetic composite material test specimen.

[0009] The split Hopkinson rod device includes: a quick-release valve, a cylinder, a bullet, an incident rod, and a test fixture. The bullet and the incident rod have the same diameter; wherein, the cylinder, bullet, and incident rod are coaxially arranged, the end of the incident rod with a wedge-shaped punch impacts the material, and the bullet impacts the other end of the incident rod; the test fixture consists of a mounting and fixing part and a movable clamp.

[0010] The speed control system includes a computer, a gas flow controller, and a gas pressure controller. In the speed control system, the computer is connected to the gas flow controller and the gas pressure controller, which are connected between the gas tank and the cylinder. The bullet is placed at the muzzle of the cylinder. The required gas pressure for the preset speed is calculated, and the gas flow controller and gas pressure controller control the amount of gas injected into the cylinder from the gas tank to obtain the required pressure. Then, the pressure inside the cylinder is released through a quick-release valve, acting on the bullet to give it the preset impact speed.

[0011] The bullet is a short, round metal rod. A quick-release valve releases the air pressure within the cylinder, driving the bullet to strike the incident rod.

[0012] The incident rod is a long, round metal rod with the same diameter and material as the bullet. One end, equipped with a wedge-shaped punch, impacts the material, while the bullet impacts the other end of the incident rod. The cylinder, bullet, and incident rod are coaxially arranged.

[0013] The test fixture includes a fixed structure and movable clamps. The fixed structure includes a base plate, ribs, and a vertical plate. Both the base plate and the vertical plate have elongated holes. The base plate is located above the test bench and can move on the test bench via bolts through the elongated holes. The movable clamps are mounted on the vertical plate and can slide within the elongated holes to adjust the test span of the specimen, which ranges from 20 to 110 mm. The biomimetic composite material test specimen is placed vertically between the two movable clamps and secured with clamping bolts. The planes of the clamps that contact the specimen support the specimen and constrain its vertical freedom. Specifically, the first and second chucks are symmetrically arranged vertically and have the same structure. Taking the first chuck as an example: the tail of the first chuck connects to the vertical plate, and the threaded screw at the tail of the chuck passes through the elongated hole in the vertical plate, securing the chuck with a nut. The head of the first chuck is a limiting plate, with semi-cylindrical limiting blocks at both ends of the bottom of the limiting plate. The test sample is placed between the two semi-cylindrical limiting blocks. An internal thread is provided in the left limiting plate, which mates with a clamping bolt. The clamping bolt passes through this hole to secure the sample. In the second chuck, semi-cylindrical limiting blocks are provided at both ends of the top of the limiting plate. The upper part of the sample is secured by the two semi-cylindrical limiting blocks of the first chuck, and the lower part of the sample is secured by the two semi-cylindrical limiting blocks of the second chuck. The biomimetic composite material test sample is placed vertically and clamped by the clamping bolt. The two movable chucks contact the sample at the limiting plate portion, and the sample is supported and secured by the limiting blocks connected to the ends of the limiting plates. The first and second clamps pass through the elongated hole and are fixed to the vertical plate by bolts.

[0014] The biomimetic composite material test specimen has an overall rectangular structure with two cylindrical support blocks at the bottom. The specimen is composed of alternating layers of hard and soft materials from the composite material. Specifically, the specimen is composed of hard and soft materials, with the soft material acting as an adhesive to bond the hard material. The support span S of the specimen is equal to four times the height W; the width B must satisfy 1 < W / B < 4; the overhang length at each end is at least 10% of the support span; the upper and lower bottom surfaces of the specimen are mostly made of hard material (if the impact area of ​​the test specimen is made of pure soft material, it will affect the test results), ensuring that the hard material is in contact with the movable clamp and the incident rod; a pre-fabricated crack is provided at the center of the specimen, and a strain gauge is attached 1 mm above the pre-fabricated crack; the strain gauge is connected to a bridge box, the bridge box is connected to a strain gauge, and the strain gauge is connected to an oscilloscope; the resistance change signal obtained from the strain gauge is output as an electrical signal by the strain gauge.

[0015] This invention provides a method for testing the dynamic fracture toughness of biomimetic composite materials, comprising the following steps:

[0016] Step 1: Adjust the bullet and the firing rod to make them coaxial with the cylinder;

[0017] Step 2: Place the sample in the test fixture and align the incident rod with the center of the sample before testing;

[0018] Step 3: Activate the speed control system, input the specified speed, and adjust the air pressure in the cylinder; then open the quick-release valve to fire the bullet from the cannon barrel and impact the incident rod, generating a stress wave that travels along the incident rod to the biomimetic composite material sample; record the reflected wave using strain gauges on the incident rod and the sample respectively, and calculate the load-displacement curve of the sample under the impact using the wave method.

[0019] The computer calculates the required air pressure for a preset speed through programming. The gas pressure in the cylinder is controlled by a gas flow controller and a gas pressure controller, based on the gas adiabatic equation: PV r =P0(V+AL) r And Newton's Second Law: P0 is the gas pressure exerted on the bullet by the high-pressure gas after the valve is opened; by combining the two equations, the relationship between the bullet's position inside the cylinder and the firing pressure and velocity can be obtained as follows:

[0020]

[0021] Wherein, the firing pressure of the cylinder is P, the volume is V, the adiabatic coefficient of the air is r, the cross-sectional area of ​​the firing chamber of the cylinder is A, the distance between the initial end of the bullet and the chamber is L, the displacement of the bullet from the moment it hits the firing rod is x, the bullet velocity is v, and the bullet mass is M.

[0022] The test specimens were subjected to a three-point bending impact test using a split Hopkinson bar. By collecting incident and reflected waves, the load-displacement curves were calculated to evaluate the fracture toughness of the biomimetic composite specimens. K is the stress intensity factor, which is used to evaluate the fracture toughness of the biomimetic composite specimens. The calculation formula is as follows:

[0023]

[0024] Where P is the critical load, S is the specimen support span, B is the specimen thickness, W is the specimen height, and a is the crack length.

[0025] The biomimetic composite material dynamic fracture toughness testing system and method provided by this invention brings the following beneficial effects:

[0026] (1) The present invention has a speed control system that can control the bullet impact speed. Compared with the traditional dynamic three-point bend test device, it has a more precise experimental setup: the bullet impact speed is controllable, which makes it easy to control variables. Therefore, experiments can be conducted on biomimetic composite material test samples with different structures, and more accurate experimental results can be obtained.

[0027] (2) The test fixture of the present invention is equipped with a movable clamp, which can adjust the span of the sample, making it convenient to test biomimetic composite structure samples of different sizes. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a split Hopkinson bar experimental setup;

[0029] Figure 2 This is a schematic diagram of the test fixture;

[0030] Figure 3 This is a schematic diagram showing the connection relationship between the clamp and the sample.

[0031] Figure 4 This is a schematic diagram of the speed control system;

[0032] Figure 5 This is a schematic diagram of a biomimetic composite material sample.

[0033] In the diagram: 1 is the cylinder, 2 is the bullet, 3 is the firing rod, 4 is the base plate, 5 is the rib plate, 6 is the vertical plate, 7 is the first clamp, 8 is the second clamp, 9 is the clamping bolt, 10 is the gas tank A, 11 is the gas tank B, 12 is the quick-release valve A, 13 is the quick-release valve B, 14 is the gas flow controller, 15 is the gas pressure controller, 16 is the quick-release valve C, 17 is the computer, 18 is the hard material, and 19 is the soft material. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] A testing system for the dynamic fracture toughness of biomimetic composite materials includes a split Hopkinson bar experimental device, a velocity control system, and biomimetic composite materials.

[0036] like Figure 1 The diagram shows the described split Hopkinson bar experimental apparatus. It includes a bullet 2, an incident rod 3, and a test fixture. The incident rod 3 is a slender metal rod, 400 mm long and 5 mm in diameter, made of spring steel, with a wedge-shaped punch at one end. The bullet 2 is 80 mm long and 5 mm in diameter, also made of spring steel. The bullet 2 impacts the incident rod 3, and the wedge-shaped punch of the incident rod 3 impacts the biomimetic composite material sample held in the fixture.

[0037] Figure 2The test fixture includes a base plate 4, a rib plate 5, a vertical plate 6, and two movable clamps. Symmetrical elongated holes on the base plate 4 are used for fixing to the test bench. Elongated holes on the vertical plate 6 are used to fix a first clamp 7 and a second clamp 8; the two clamps can slide vertically within the elongated holes. The first clamp 7 and the second clamp 8 are symmetrically arranged vertically and have the same structure. Taking the first clamp as an example: the tail of the first clamp 7 is connected to the vertical plate 6, and the threaded screw at the tail of the clamp passes through the elongated hole of the vertical plate 6, securing the clamp with a nut. The head of the first clamp 7 is a limiting plate, with semi-cylindrical limiting blocks at both ends of the bottom of the limiting plate. The test sample is placed between the two semi-cylindrical limiting blocks. An internal thread is provided in the left limiting plate, which cooperates with a clamping bolt 9. The clamping bolt 9 passes through this hole to fix the sample. In the second clamp 8, semi-cylindrical limiting blocks are provided at both ends of the top of the limiting plate, such as... Figure 3 As shown. The upper part of the sample is fixed by two semi-cylindrical limiting blocks of the first clamp 7, and the lower part of the sample is fixed by two semi-cylindrical limiting blocks of the second clamp 8.

[0038] The biomimetic composite material test specimen is placed vertically (e.g.) Figure 2 and Figure 3 As shown, the sample is clamped and fixed by clamping bolts 9. The two movable clamps are in contact with the sample at the position of the limiting plate, and the sample is supported and fixed by the limiting block connected to the end of the limiting plate. The first clamp 7 and the second clamp 8 are fixed to the vertical plate 6 by bolts through the elongated hole.

[0039] The incident rod 3 has the same diameter and material as the bullet 2, and the length of the incident rod 3 is 5 times the length of the bullet 2.

[0040] like Figure 4 As shown, the speed control system includes cylinder 1, gas tank A10, gas tank B11, quick-release valve A12, quick-release valve B13, gas flow controller 14, gas pressure controller 15, quick-release valve C16, and computer 17. Gas tank A10 is connected to gas flow controller 14 via quick-release valve A12, and gas flow controller 14 controls the flow rate of nitrogen. Gas tank B11 is connected to gas pressure controller 15 via quick-release valve B13, and gas pressure controller 15 controls the pressure of nitrogen.

[0041] The required air pressure for a preset speed is calculated through programming. The gas pressure in the cylinder is controlled by a gas flow controller and a gas pressure controller, based on the gas adiabatic equation: PV r =P0(V+AL) r And Newton's Second Law: P0 is the gas pressure exerted on the bullet by the high-pressure gas after the valve is opened; by combining the two equations, the relationship between the bullet's position inside the cylinder and the firing pressure and velocity can be obtained as follows:

[0042]

[0043] Wherein, the firing pressure of the cylinder is P, the volume is V, the adiabatic coefficient of the air is r, the cross-sectional area of ​​the firing chamber of the cylinder is A, the distance between the initial end of the bullet and the chamber is L, the displacement of the bullet from the moment it hits the firing rod is x, the bullet velocity is v, and the bullet mass is M.

[0044] The experiment's preset speed is 10 m / s. Computer 17 calculates the gas pressure required for the set firing speed using the above formula, which is 0.046 MPa. Gas pressure controller 15 precisely controls the nitrogen pressure in cylinder 1 to maintain the nitrogen pressure at 0.046 MPa. The pressure in cylinder 1 is released through quick-release valve C16, and the bullet is placed in the firing chamber of the cylinder, driving bullet 2 to strike the firing rod 3.

[0045] like Figure 5 The image shows the biomimetic composite material test specimen. The specimen is composed of a hard material 18 and a soft material 19, with the soft material 19 acting as an adhesive to bond the hard material 18. The support span S of the specimen is equal to four times the height W; the width B must satisfy 1 < W / B < 4; the overhang length at each end is at least 10% of the support span. The model length L of the biomimetic composite material test specimen is 72 mm, the height W is 13 mm, the width B is 5 mm, the support span S is 52 mm, and the pre-fabricated crack length a is 7.5 mm. The dimensions are designed so that the upper and lower bottom surfaces of the specimen are mostly made of hard material 17, ensuring that the hard material 17 is in contact with the movable clamps 7 and 8 and the incident rod 3.

[0046] The following describes the implementation process used in the experiment:

[0047] A test method for the dynamic fracture toughness of biomimetic composite materials includes the following steps:

[0048] Step 1: Adjust the bullet and the firing rod to make them coaxial with the cylinder;

[0049] Before the experiment begins, strain gauges need to be attached to the incident rod 3 at a distance of 1 / 3 of the total length of the incident rod 3, close to the end of the incident rod 3 where the bullet 2 impacts. Strain gauges are also attached to the biomimetic composite material specimen, approximately 1 mm above the pre-fabricated crack opening.

[0050] Step 2: Place the sample in the test fixture and align the incident rod with the center of the sample before testing;

[0051] At the start of the experiment, the sample is placed on the first chuck 7 and the second chuck 8 (the sample is located between the two chucks, and the central crack hole corresponds to the center position of the two chucks). The end of the incident rod 3 with the wedge-shaped punch is pressed tightly against the sample. Then, the sample and the strain gauge attached to the incident rod 3 are connected to the bridge box. The bridge box is connected to the strain gauge, and the strain gauge is connected to the oscilloscope. The oscilloscope acquires the signal and can output the resistance change signal obtained from the strain gauge as an electrical signal through the strain gauge.

[0052] Step 3: Activate the speed control system, input the specified speed, and adjust the air pressure in the cylinder; then open the quick-release valve to fire the bullet from the cannon barrel and impact the incident rod, generating a stress wave that travels along the incident rod to the biomimetic composite material sample; record the reflected wave using strain gauges on the incident rod and the sample respectively, and calculate the load-displacement curve of the sample under the impact using the wave method.

[0053] The computer calculates the required air pressure for a preset speed through programming. The gas pressure in the cylinder is controlled by a gas flow controller and a gas pressure controller, based on the gas adiabatic equation: PV r =P0(V+AL) r And Newton's Second Law: P0 is the gas pressure exerted on the bullet by the high-pressure gas after the valve is opened; by combining the two equations, the relationship between the bullet's position inside the cylinder and the firing pressure and velocity can be obtained as follows:

[0054]

[0055] Wherein, the firing pressure of the cylinder is P, the volume is V, the adiabatic coefficient of the air is r, the cross-sectional area of ​​the firing chamber of the cylinder is A, the distance between the initial end of the bullet and the chamber is L, the displacement of the bullet from the moment it hits the firing rod is x, the bullet velocity is v, and the bullet mass is M.

[0056] The test specimens were subjected to a three-point bending impact test using a split Hopkinson bar. By collecting incident and reflected waves, the load-displacement curves were calculated to evaluate the fracture toughness of the biomimetic composite specimens. K is the stress intensity factor, which is used to evaluate the fracture toughness of the biomimetic composite specimens. The calculation formula is as follows:

[0057]

[0058] Where P is the critical load, S is the specimen support span, B is the specimen thickness, W is the specimen height, and a is the crack length.

[0059] Specifically, a specified speed of 10 m / s is input to computer 17, and the required gas pressure of 0.046 MPa is calculated. The nitrogen pressure in cylinder 1 is controlled to 0.046 MPa via gas flow controller 14 and gas pressure controller 15. Finally, the pressure in cylinder 1 is released through quick-release valve C16, driving bullet 2 to impact the incident rod 3 at a speed of 10 m / s. The incident rod 3 receives the load and impact on the sample. The waveform data acquired in the oscilloscope is saved, completing one test. Based on the signal obtained from the incident rod 3, the load-displacement curve of the sample is obtained through wave method calculation. The signal obtained from the sample can determine the crack initiation time. The above operation is repeated to complete multiple experiments. Finally, the dynamic fracture toughness of the biomimetic composite material is obtained through calculation.

Claims

1. A testing system for the dynamic fracture toughness of biomimetic composite materials, characterized in that: The device includes a speed control system, a detachable Hopkinson bar device, and a biomimetic composite material test specimen. The detachable Hopkinson bar device comprises a quick-release valve, a cylinder, a bullet, an incident rod, and a test fixture. The bullet and the incident rod have the same diameter. The cylinder, bullet, and incident rod are coaxially arranged. One end of the incident rod, equipped with a wedge-shaped punch, impacts the material, while the bullet impacts the other end of the incident rod. The test fixture includes a base plate, ribs, a vertical plate, and two movable clamps. The base plate has symmetrical elongated holes for fixing to the test bench, and the base plate can move on the test bench. The ribs and vertical plate are welded to the base plate. The vertical plate has two elongated holes for fixing the movable clamps. The movable clamps pass through the elongated holes on the vertical plate and are fixed with bolts. The clamps slide up and down within the elongated holes to adjust the test span of the specimen. The bolts on the clamps clamp the specimen. The design facilitates sample position adjustment. Two movable clamps, designated as the first clamp and the second clamp, are symmetrically arranged vertically and have identical structures. The tail of the first clamp connects to the vertical plate, and a threaded screw at the tail passes through a long hole in the vertical plate, securing the clamp with a nut. The head of the first clamp is a limiting plate with semi-cylindrical limiting blocks at both ends of its bottom. The test sample is placed between these two semi-cylindrical limiting blocks. An internal thread is present in the left limiting plate, engaging with a clamping bolt, which passes through this hole to secure the sample. In the second clamp, semi-cylindrical limiting blocks are located at both ends of the top of the limiting plate. The upper part of the sample is secured by the two semi-cylindrical limiting blocks of the first clamp, and the lower part is secured by the two semi-cylindrical limiting blocks of the second clamp. Both the first and second clamps are secured to the vertical plate through the long hole using bolts. The speed control system includes gas tank A, gas tank B, quick-release valve A, quick-release valve B, gas flow controller, gas pressure controller, quick-release valve C, cylinder, and computer. Gas tank A is connected to the gas flow controller via quick-release valve A, which controls the flow rate of nitrogen. Gas tank B is connected to the gas pressure controller via quick-release valve B, which controls the pressure of nitrogen. The computer is connected to the gas flow controller and the gas pressure controller, which are connected between the gas tanks and the cylinder. The bullet is placed at the muzzle of the cylinder. The required gas pressure for the preset speed is calculated, and the gas flow controller and gas pressure controller control the amount of gas filled into the cylinder from the gas tanks to obtain the required gas pressure. The pressure inside the cylinder is then released through the quick-release valve, acting on the bullet to give it the preset impact speed. The relationship between the bullet's position inside the cylinder and the firing gas pressure and speed is as follows: ； Wherein, the firing pressure of the cylinder is P, the volume is V, the adiabatic coefficient of the air is r, the cross-sectional area of ​​the firing chamber of the cylinder is A, the distance between the initial end of the bullet and the chamber is L, the displacement of the bullet from the moment it hits the firing rod is x, the bullet velocity is v, and the bullet mass is M.

2. The testing system for dynamic fracture toughness of biomimetic composite materials as described in claim 1, characterized in that: The incident rod is a slender metal rod with a wedge-shaped punch at one end. When the bullet hits the incident rod, the wedge-shaped punch of the incident rod impacts the biomimetic composite material sample held by the fixture. Strain gauges are attached to the incident rod to receive test signals and record incident and reflected waves.

3. The testing system for dynamic fracture toughness of biomimetic composite materials as described in claim 2, characterized in that: The incident rod has the same diameter and material as the bullet, and its length is 5 times that of the bullet. The strain gauge is positioned at one-third of the total length of the incident rod, near the end of the rod where the bullet impacts.

4. The testing system for dynamic fracture toughness of biomimetic composite materials as described in claim 1, characterized in that: The biomimetic composite test specimen has an overall rectangular structure, composed of alternating layers of hard and soft materials. The soft material acts as an adhesive, bonding the hard material together. The support span S of the specimen is equal to four times its height W. The width B must satisfy 1 < W / B < 4. The overhang length at each end is at least 10% of the support span. The top and bottom surfaces of the specimen are mostly made of hard material to ensure contact between the hard material and the movable clamp and the incident rod. A pre-fabricated crack is provided at the center of the specimen, and a strain gauge is attached 1 mm above the pre-fabricated crack. The strain gauge is connected to a bridge box, which is connected to a strain gauge, which is connected to an oscilloscope. The resistance change signal obtained from the strain gauge is output as an electrical signal by the strain gauge.

5. A method for testing the dynamic fracture toughness of biomimetic composite materials, using the testing system for the dynamic fracture toughness of biomimetic composite materials as described in any one of claims 1 to 4, characterized in that... Includes the following steps: Step 1. Adjust the bullet and the firing rod to make them coaxial with the cylinder; Step 2. Place the sample in the test fixture and align the incident rod with the center of the sample before testing; Step 3. Activate the speed control system, input the specified speed, and adjust the air pressure in the cylinder; then open the quick-release valve to fire the bullet from the cannon barrel and impact the incident rod, generating a stress wave that travels along the incident rod to the biomimetic composite material sample; record the reflected wave using strain gauges on the incident rod and the sample respectively, and calculate the load-displacement curve of the sample under the impact using the wave method.

6. The method for testing the dynamic fracture toughness of biomimetic composite materials according to claim 5, characterized in that: The test specimens were subjected to a three-point bending impact test using a split Hopkinson bar. By collecting incident and reflected waves, the load-displacement curves were calculated to evaluate the fracture toughness of the biomimetic composite specimens. K is the stress intensity factor, which is used to evaluate the fracture toughness of the biomimetic composite specimens. The calculation formula is as follows: ； Where P is the critical load, S is the specimen support span, B is the specimen thickness, W is the specimen height, and a is the crack length.

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