Method and apparatus for testing the interfacial strength of continuous fiber reinforced composites

Abstract

A method and apparatus for testing the interfacial strength of 3D-printed continuous fiber-reinforced composite materials are disclosed. In the method, a single-layer, single-pass continuous fiber-reinforced composite material sample is formed by 3D printing. The cross-section is photographed to obtain the interfacial morphology and dimensions of the sample, and the fiber bundle dimensions are obtained through image processing. The thermoplastic resin matrix in the middle region of the sample is dissolved by organic solvent drop coating to obtain fiber bundles, while the matrix at both ends is retained to form the sample for testing. One end of the sample is held in place by two adjustable sliders, and the other end of the sample is clamped by a fixture and loaded onto a universal testing machine for tensile testing. The movement of the upper slider and the lower fixture causes the fiber bundles of the sample to peel off from the matrix at both ends, and the load-displacement curve is recorded. The fiber bundle-matrix interfacial strength is obtained based on the fiber bundle dimensions and the load-displacement curve.

Description

Technical Field

[0001] This invention belongs to the field of continuous fiber reinforced composite material testing technology, and in particular, it is a method and apparatus for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials. Background Technology

[0002] 3D printing technology can be used to prepare continuous fiber-reinforced composites, eliminating the reliance on molds in traditional molding and autoclave manufacturing processes and enabling the creation of arbitrarily complex structures. However, due to the high viscosity of thermoplastic resins, the low molding pressure, and the short wetting time between the fiber bundles and the resin matrix during printing, the interfacial bonding between the fiber bundles and the matrix is ​​poor, severely affecting the overall mechanical properties of the printed parts. Furthermore, testing the interfacial strength of 3D-printed continuous fiber-reinforced composites remains challenging. Traditional fiber pull-out tests, fiber ejection tests, and microdroplet embedding and debonding tests are only applicable to the microscopic interfacial properties of a single fiber with the matrix. However, the overall performance of 3D-printed continuous fiber-reinforced composites is primarily determined by the interfacial properties between the fiber bundles (above 1 kilometer) and the matrix. Existing microscopic testing methods for single-fiber interfacial strength cannot test the macroscopic interfacial properties of the entire fiber bundle.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a method and apparatus for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials. It can test the fiber bundle-matrix interfacial strength of 3D printed continuous fiber reinforced composite materials, and is applicable to different types of fiber bundle materials, pre-impregnation processes and processing and molding processes. It can be used to evaluate the interfacial performance of 3D printed continuous fiber composite materials and guide process improvement, material modification and equipment upgrade.

[0005] The objective of this invention is achieved through the following technical solution: a method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials includes:

[0006] 3D printing forms a single-layer, single-pass continuous fiber-reinforced composite material sample. Cross-sectional photography is used to obtain the interface morphology and dimensions of the sample, and image processing is used to obtain the fiber bundle dimensions.

[0007] Organic solvent drop coating dissolves the thermoplastic resin matrix in the middle region of the sample to obtain fiber bundles, while retaining the matrix at both ends to form the test sample;

[0008] One end of the specimen is held in place by two adjustable sliders, and the other end of the specimen is clamped by a fixture and loaded onto a universal testing machine for tensile testing. The movement of the upper slider and the lower fixture causes the fiber bundle of the specimen to peel off from the matrix at both ends. At the same time, the load-displacement curve is recorded. The fiber bundle-matrix interface strength is obtained based on the fiber bundle size and the load-displacement curve.

[0009] In the method for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials, a sample of a single-layer, single-pass continuous fiber reinforced thermoplastic composite material is obtained by melt extrusion molding.

[0010] In the method for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials, an organic solvent is drawn up with a dropper and dissolved in the thermoplastic resin matrix in the middle region of the sample by adding it drop by drop, and then dried with a hot air gun.

[0011] In the method for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials, the single-pass width of the matrix is ​​1.0-1.6 mm, the layer height is 0.2-0.3 mm, and the length is 40-60 mm.

[0012] A testing apparatus for implementing the method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials includes,

[0013] The upper clamp is detachably connected to the universal testing machine;

[0014] The upper base is fixedly connected to the upper clamp;

[0015] A pair of sliders, the spacing of which is adjustable, are disposed on the upper base. The sliders include a horizontal section detachably connected to the upper base and a vertical section extending vertically downward from the horizontal section. The horizontal section has an elongated slot for adjusting the spacing between the two sliders. One end of the sample is detachably fixed to the vertical section.

[0016] A pair of movable sliders are movably connected to the upper base to clamp the fiber bundle.

[0017] The lower end clamp is detachably connected to the universal testing machine;

[0018] The lower base is fixedly connected to the lower clamp;

[0019] The lower end clamp is fixedly connected to the lower end base and clamps the other end of the sample.

[0020] In the aforementioned testing device, the movable slider includes an elongated slot for adjusting the distance between the two movable sliders.

[0021] In the aforementioned testing device, the vertical section is provided with multiple fixing holes for connecting screws.

[0022] In the aforementioned testing device, the upper clamp, the sample, and the lower clamp are collinear.

[0023] The testing device described herein has a symmetrical structure.

[0024] In the aforementioned testing device, the test device performs tensile testing at a speed of 0.5 mm / min.

[0025] Compared with the prior art, the present invention has the following advantages: The method for testing the interface strength of 3D printed continuous fiber reinforced composite materials is simple and easy to implement, applicable to the evaluation of the fiber bundle-matrix interface strength of continuous fiber reinforced composite materials prepared by various 3D printing processes, and can accurately test the macroscopic interface performance of the entire fiber bundle, which helps to solve the problem of poor interfacial bonding between the fiber bundle and the matrix. Attached Figure Description

[0026] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0027] In the attached diagram:

[0028] Figure 1 This is a schematic diagram of a sample for testing the interfacial strength of a 3D-printed continuous fiber reinforced composite material according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the testing apparatus for a method of testing the interfacial strength of 3D printed continuous fiber reinforced composite materials according to an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the slider structure of a testing device for a method of testing the interfacial strength of 3D printed continuous fiber reinforced composite materials according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the movable slider structure of a testing device for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials according to an embodiment of the present invention.

[0032] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0033] The following will refer to the appendix. Figures 1 to 4Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0034] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0035] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0036] Methods for testing the interfacial strength of 3D-printed continuous carbon fiber reinforced composites include,

[0037] 3D printing forms a single-layer, single-pass continuous fiber-reinforced composite material sample. Cross-sectional photography is used to obtain the interface morphology and dimensions of the sample, and image processing is used to obtain the fiber bundle dimensions.

[0038] Organic solvent drop casting dissolves the polylactic acid matrix in the middle region of the sample to obtain carbon fiber bundles 10, while retaining the matrix 11 at both ends to form the test sample 4. Figure 1 As shown;

[0039] One end of the specimen 4 is held in place by two adjustable sliders, and the other end of the specimen 4 is clamped by a fixture and loaded onto a universal testing machine for tensile testing. The movement of the upper slider and the lower fixture causes the carbon fiber bundle 10 of the specimen 4 to peel off from the matrix 11 at both ends. At the same time, the load-displacement curve is recorded. The interfacial strength of the fiber bundle-matrix 11 is obtained based on the fiber bundle size and the load-displacement curve.

[0040] In a preferred embodiment of the method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials, sample 4 of a single-layer, single-pass continuous carbon fiber reinforced polylactic acid composite material is produced by melt extrusion molding.

[0041] In a preferred embodiment of the method for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials, dichloromethane is drawn up with a dropper and dissolved in the polylactic acid matrix in the middle region of sample 4 by adding it drop by drop, and then dried with a hot air gun.

[0042] In a preferred embodiment of the method for testing the interfacial strength of 3D printed continuous fiber reinforced composite materials, the sample has a single-pass width of 1.4 mm, a layer height of 0.3 mm, and a length of 60 mm.

[0043] In one embodiment, the method includes printing a single-layer, single-pass fiber-reinforced composite material using 3D printing technology, dissolving the matrix 11 material in the middle region using an organic solvent drop-casting method, retaining the matrix material at both ends, and preparing a test specimen 4. Using this testing apparatus, one end of the test specimen 4 is held in place by two adjustable sliders 3 with a gap slightly larger than the fiber bundle thickness, and a movable slider 5 is used to restrict the deflection of the specimen 4 during the stress process. The other end of the specimen 4 is securely clamped with a fixture. The fixture is mounted on a universal testing machine, and a tensile test is conducted. The upper and lower bases respectively drive the upper slider and the lower fixture 7 to move, causing the carbon fiber bundle 10 to peel off from the matrix 11 material. During the test, the load-displacement curve is recorded, and the fiber bundle-matrix 11 interface strength is calculated using a formula.

[0044] like Figures 2 to 4 As shown, the testing apparatus for implementing the method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials includes,

[0045] The upper clamp 1 is detachably connected to the universal testing machine;

[0046] The upper base 2 is fixedly connected to the upper clamp 1;

[0047] A pair of sliders 3 are disposed on the upper base 2 with adjustable spacing. The sliders include a horizontal section detachably connected to the upper base 2 and a vertical section extending vertically downward from the horizontal section. The horizontal section has an elongated slot for adjusting the spacing between the two sliders 3. One end of the sample 4 is detachably fixed to the vertical section.

[0048] A pair of movable sliders 5 are movably connected to the upper base 2 to clamp the carbon fiber bundle 10;

[0049] The lower end clamp 9 is detachably connected to the universal testing machine;

[0050] The lower base 6 is fixedly connected to the lower clamp 9;

[0051] The lower clamp 7 is fixedly connected to the lower base 6 and clamps the other end of the sample 4.

[0052] In a preferred embodiment of the testing device, the movable slider 5 includes an elongated slot for adjusting the distance between the two movable sliders 5.

[0053] In a preferred embodiment of the testing device, the vertical section is provided with multiple fixing holes for connecting screws 8.

[0054] In a preferred embodiment of the testing device, the upper clamp 1, the sample 4, and the lower clamp 9 are collinear.

[0055] In a preferred embodiment of the testing device, the testing device has a symmetrical structure.

[0056] In a preferred embodiment of the testing device, the testing device performs tensile testing at a speed of 0.5 mm / min.

[0057] In one embodiment, a single-layer, single-pass continuous carbon fiber reinforced polylactic acid composite sample 4 was printed using melt extrusion molding technology. A cross-sectional photograph was taken to obtain the interface morphology and dimensions, and the fiber bundle dimensions were obtained using image processing software. The single-pass width was 1.4 mm, the layer height was 0.3 mm, and the length was 60 mm. Dichloromethane was added dropwise to dissolve the polylactic acid matrix 11 in the middle region of sample 4. The sample was then dried using a hot air gun to obtain… Figure 1 The sample 4 to be tested is shown. The sample 4 to be tested is clamped in... Figure 2 In the hole of the movable slider 5, the gap size is controlled to be 0.05mm using a feeler gauge. Tighten the fastening screw 8. The end of the test sample 4 is limited by the slider 3 to keep it vertical and is secured by the screw 8. The lower end of the test sample 4 is secured with the lower fastener. The upper clamp 1 and the lower clamp 9 are respectively secured to the upper and lower fixtures of the universal testing machine, and a tensile test is performed at a speed of 0.5mm / min. The load-displacement curve is measured to obtain the maximum load.

[0058] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials, characterized in that, It includes the following steps, 3D printing forms a single-layer, single-pass continuous fiber-reinforced composite material sample. Cross-sectional photography is used to obtain the interface morphology and dimensions of the sample, and image processing is used to obtain the fiber bundle dimensions. Organic solvent drop coating dissolves the thermoplastic resin matrix in the middle region of the sample to obtain fiber bundles, while retaining the matrix at both ends to form the test sample; One end of the specimen is held in place by two adjustable sliders, and the other end of the specimen is clamped by a fixture and loaded onto a universal testing machine for tensile testing. The movement of the upper slider and the lower fixture causes the fiber bundle of the specimen to peel off from the matrix at both ends. At the same time, the load-displacement curve is recorded. The fiber bundle-matrix interface strength is obtained based on the fiber bundle size and the load-displacement curve.

2. The method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials according to claim 1, characterized in that, Samples of single-layer, single-pass continuous fiber-reinforced polylactic acid composite materials were formed by melt extrusion 3D printing.

3. The method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials according to claim 2, characterized in that, The organic solvent was drawn up with a dropper and dissolved in the thermoplastic resin matrix in the middle area of ​​the sample by adding it drop by drop. The sample was then dried with a hot air gun.

4. The method for testing the interfacial strength of 3D-printed continuous fiber reinforced composite materials according to claim 1, characterized in that, The single-layer width of the substrate is 1.0~1.6mm, the layer height is 0.2~0.3mm, and the length is 40~60mm.

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