Method for measuring shear modulus of two-dimensional woven fabric reinforced composite material

Abstract

The present invention relates to the field of the characterization of mechanical properties of fabric reinforced composite materials. Disclosed is a method for measuring the shear modulus of a two-dimensional woven fabric reinforced composite material on the basis of a unidirectional tensile test, comprising: step 1, selecting a composite material reinforcement to be characterized (a plain weave fabric, a twill weave fabric, or a satin weave fabric, etc.), which is used for preparing a laminate laid in the same direction, and cutting same into a plurality of test pieces, the cutting directions being parallel to the warp and weft directions of a two-dimensional woven fabric reinforced composite material or forming an included angle of + / −45° with the warp and weft directions of the two-dimensional woven fabric reinforced composite material; step 2, separately performing a tensile test on a test piece obtained by cutting along yarn directions and a test piece obtained by cutting along oblique directions of + / −45°, and recording test data; and step 3, in view of the data in step 2, acquiring shear mechanical properties of the two-dimensional woven fabric reinforced composite material when subjected to in-plane shearing in the warp direction and the weft direction or in directions forming an included angle of + / −45° with the warp and the weft. According to the present invention, the shear mechanical properties of the two-dimensional woven fabric reinforced composite material can be acquired simply by means of uniaxial tensile testing of a unidirectional laminate.

Description

Method for measuring shear modulus of two-dimensional woven fabric reinforced composite material TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical property characterization of fabric reinforced composite material, and particularly relates to a method for measuring shear modulus of two-dimensional woven fabric reinforced composite material. BACKGROUND

[0002] In the production of composite parts by using two-dimensional woven fabric prepreg or liquid forming process, the woven fabric reinforced composite material has obvious cost advantage while ensuring the mechanical properties. In actual engineering application, two-dimensional woven fabric reinforced composite material parts appear in the form of multi-directional layer laminates, and accurately characterizing the performance of two-dimensional woven fabric reinforced composite material itself is an important basis before laminate design.

[0003] In order to obtain the shear modulus of two-dimensional woven fabric reinforced composite material, the commonly used methods at present include track shear test (the standards that can be referred to include ASTM D5379, ASTM D7078, etc.) or ±45° laminate tensile test (the standards that can be referred to include ASTM D3518, ISO 14129, etc.). The track shear test needs complex clamps and operation process, and the ±45° laminate tensile test avoids the disadvantages of shear test, but still needs to prepare special ±45° symmetrically layered laminates. If the uniaxial tensile test is performed on the two-dimensional fabric composite test piece with unidirectional layer, the in-plane shear modulus and shear response curve of the material can be measured, the inherent defects of shear test can be avoided, the process of preparing laminates in the form of ±45° symmetrically layered can be avoided, and at the same time, the tensile performance of the test piece in the tensile direction can be obtained, which has certain practical significance. SUMMARY

[0004] The purpose of the present application is to provide a method for measuring shear modulus of two-dimensional woven fabric reinforced composite material, so as to solve the problems existing in the prior art, and to obtain the shear mechanical properties of two-dimensional woven fabric reinforced composite material only by uniaxial tensile test on unidirectional layered laminates.

[0005] In order to achieve the above purpose, the present application provides the following solutions:

[0006] The present application provides a method for measuring shear modulus of two-dimensional woven fabric reinforced composite material, comprising:

[0007] Step 1: selecting plain fabric, twill fabric or satin fabric, for preparing two-dimensional woven fabric reinforced composite material laminates with unidirectional layer, and cutting the prepared two-dimensional woven fabric reinforced composite material laminates with unidirectional layer into a plurality of test pieces, and the cutting direction is parallel to or at ±45° angle with the warp and weft directions of the two-dimensional woven fabric reinforced composite material.

[0008] Step two, respectively select the test piece parallel to the warp yarn direction, parallel to the weft yarn direction and ± 45° angle with the yarn direction respectively to carry out tensile loading test, and record the test data;

[0009] Step three, combined with step two data, obtain the shear mechanical properties of the material along the warp and weft directions and along the direction with ± 45° angle with the warp and weft.

[0010] Optionally, for the 0° / 90° direction test piece, the cross-sectional area of the test piece is , when carrying out tensile test, the load of the mth data point is , the longitudinal normal strain of the mth data point is , the transverse normal strain is , the tensile modulus measured in the elastic interval of stress-strain line is , and the Poisson's ratio is .

[0011] Optionally, for the ± 45° direction test piece, the cross-sectional area of the test piece is , when carrying out tensile test, the load of the nth data point is , the longitudinal normal strain of the nth data point is , the transverse normal strain is , the tensile modulus measured in the elastic interval of stress-strain line is , and the Poisson's ratio is .

[0012] Optionally, the calculation method of the shear modulus G 45 of the material in the direction with ± 45° angle with the yarn direction of the two-dimensional woven fabric reinforced composite material is as follows:

[0013] Optionally, the calculation method of the shear modulus of the material in the direction parallel to the yarn direction of the two-dimensional woven fabric reinforced composite material is as follows:

[0014] Optionally, when the two-dimensional woven fabric reinforced composite material is sheared along a direction with an angle of ±45° with the warp and weft yarns, the abscissa of the mth data point on the shear stress-strain curve in the direction is , and the ordinate of the mth data point on the shear stress-strain curve in the direction is .

[0015] Optionally, when the two-dimensional woven fabric reinforced composite material is sheared along the direction of the warp and weft yarns, the abscissa of the nth data point on the shear stress-strain curve in the direction is , and the ordinate of the nth data point on the shear stress-strain curve in the direction is .

[0016] The present application has the following technical effects relative to the prior art:

[0017] The uniaxial tensile test adopted by the present application is one of the most common mechanical property tests, and the required equipment is simple and easy to operate. In comparison, the fixture required for the plane shear test and the preparation of the test piece are more complex and more difficult to operate.

[0018] Compared with the widely used ±45° laminate tensile test method, the present method does not require a separately prepared ±45° symmetrically laminated laminate, but only requires a unidirectional laminated laminate that is the same as the tensile and compression tests. Therefore, the unidirectional laminated method adopted by the present method not only reduces the additional process of test piece preparation, but also eliminates the need for separately preparing a unidirectional laminated laminate for cutting and measuring the tensile mechanical properties of the tensile test piece when the mechanical properties (tensile properties and shear properties) of the two-dimensional woven fabric reinforced composite material need to be fully characterized. This can achieve the effect of one laminate and two tensile test pieces for fully characterizing the mechanical properties of the material. On the other hand, the ±45° laminate tensile test method can only be used to measure the shear mechanical properties along the yarn or fiber direction. The present method can not only be used to measure the shear mechanical properties along the yarn or fiber direction, but also be used to measure the shear mechanical properties in a direction with an angle of ±45° with the yarn or fiber direction.

[0019] The two-dimensional woven fabric reinforced composite material shear modulus measurement method based on the uniaxial tensile test of the present application replaces the shear test by measuring the tensile properties in the 0° / 90° and ±45° two direction combinations, and cooperates with a unique calculation method to achieve the purpose of characterizing the shear mechanical properties of the two-dimensional woven fabric reinforced composite material only through the uniaxial tensile test of the unidirectional laminated test piece, thereby reducing the complexity of characterizing the shear mechanical properties of the two-dimensional woven fabric reinforced composite material. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below only constitute some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0021] Fig. 1 is a schematic diagram of a unidirectional lay-up two-dimensional woven fabric reinforced composite laminate and partial yarns;

[0022] Fig. 2 is a schematic diagram of a test piece with the cutting direction being 0° to the warp direction of the yarns;

[0023] Fig. 3 is a schematic diagram of a test piece with the cutting direction being 90° to the warp direction of the yarns;

[0024] Fig. 4 is a schematic diagram of a test piece with the cutting direction being +45° to the warp direction of the yarns;

[0025] Fig. 5 is a schematic diagram of a test piece with the cutting direction being -45° to the warp direction of the yarns;

[0026] Fig. 6 is a schematic diagram of the process of cutting a test piece along the warp direction and the +45° direction according to the present application;

[0027] Fig. 7 is a schematic diagram of the process of cutting a test piece along the weft direction and the -45° direction according to the present application;

[0028] Fig. 8 is a schematic diagram of a plain weave fabric;

[0029] Fig. 9 is a schematic diagram of a twill weave fabric;

[0030] Fig. 10 is a schematic diagram of a satin weave fabric; DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, and all other embodiments obtained by those of ordinary skill in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0032] The present application aims to provide a two-dimensional woven fabric reinforced composite shear modulus measurement method to solve the problems in the prior art, and can measure the in-plane shear mechanical properties of two-dimensional woven fabric reinforced composites only through uniaxial tensile test of unidirectional lay-up test pieces.

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0034] The embodiment provides a two-dimensional woven fabric reinforced composite shear modulus measurement method. In order to measure the shear modulus of the two-dimensional woven fabric reinforced composite, a test piece is cut along the yarn direction of a unidirectional lay-up two-dimensional woven fabric reinforced composite laminate and a direction deviating from the yarn by +45°, and a tensile test is performed, so that the in-plane shear mechanical properties of the material can be obtained. Since the thickness of the single-layer composite (Lamina) is extremely thin, it is difficult to carry out test testing. The unidirectional lay-up is a composite material manufacturing process, and the thickness of the test piece is increased by unidirectional lay-up to manufacture a unidirectional laminate, so as to measure the basic mechanical properties of the single-layer composite (Lamina). In the unidirectional lay-up process, the fiber band can be a very narrow band or a wider fabric form, and the number of layers is laid according to a certain number of layers, but their common characteristic is that the fibers between all the layers are almost completely parallel. The reason why the method adopts the way of preparing the laminate by unidirectional lay-up is to equivalent the performance of the single-layer material (Lamina) by the performance obtained by the mechanical test on the unidirectional laminate (Laminate), and then used for the design of the multi-directional lay-up laminate in the subsequent engineering scene. The test piece cut along the +45° direction (namely, the +45° direction test piece) and the test piece cut along the-45° direction (namely, the-45° direction test piece) can be replaced with each other, and the test piece cut along the warp direction (namely, the 0° direction test piece) and the test piece cut along the weft direction (namely, the 90° direction test piece) can be replaced with each other. The two-dimensional woven fabric reinforced composite shear modulus measurement method of the embodiment is suitable for a wide range of fabric types, and can be applied to, for example, the plain fabric shown in FIG. 8, the twill fabric shown in FIG. 9, and the satin fabric shown in FIG. 10. The embodiment specifically takes the twill fabric composite material as an example for description.

[0035] Specifically includes the following steps:

[0036] Step 1, test piece preparation

[0037] Step 1.1: Prepare a unidirectional lay-up two-dimensional woven fabric reinforced composite laminate. FIG. 1 is a local schematic diagram of a unidirectional lay-up two-dimensional woven fabric reinforced composite laminate prepared in the embodiment, taking a twill fabric composite material as an example.

[0038] Step 1.2: Cutting test piece

[0039] Fig. 2, Fig. 3, Fig. 4 and Fig. 5 are schematic diagrams of test pieces cut in different directions, and Fig. 6 and Fig. 7 are schematic diagrams of the process of cutting test pieces in different directions. Fig. 2 is a 0° direction test piece, the length direction of which is parallel to the warp direction of the yarn; Fig. 3 is a 90° direction test piece, the length direction of which is parallel to the weft direction of the yarn; Fig. 4 is a +45° direction test piece, the length direction of which forms a +45° angle with the warp direction; and Fig. 5 is a -45° direction test piece, the length direction of which forms a -45° angle with the warp direction.

[0040] Step 2: Tensile test

[0041] Step 2.1: Tensile test of the 0° direction test piece or the 90° direction test piece.

[0042] Measure the initial cross-sectional area of the test piece in Fig. 2 or Fig. 3 , and load it in tension, and record the data of each measuring point, including the load of the mth measuring point , the longitudinal normal strain , and the transverse normal strain . The tensile modulus and the Poisson's ratio in the elastic interval of the stress-strain curve are measured.

[0043] Step 2.2: Tensile test of the +45° direction test piece or the -45° direction test piece.

[0044] Measure the initial cross-sectional area of the test piece in Fig. 4 or Fig. 5 , and load it in tension, and record the data of each measuring point, including the load of the nth measuring point , the longitudinal normal strain , and the transverse normal strain . The tensile modulus and the Poisson's ratio in the elastic interval of the stress-strain curve are measured.

[0045] Step 3: Calculate the shear mechanical properties

[0046] Calculate the shear mechanical properties of the material from the experimental data in Step 2.

[0047]

[0048] In formula (1) to formula (6), is the tensile modulus measured in the elastic interval of the stress-strain curve when the 0° direction test piece or the 90° direction test piece is subjected to the tensile test, is the Poisson's ratio measured in the elastic interval of the stress-strain curve when the 0° direction test piece or the 90° direction test piece is subjected to the tensile test, the tensile modulus measured in the elastic region of the stress-strain curve when the tensile test is performed on the test piece in the +45° direction or in the -45° direction, the Poisson's ratio measured in the elastic region of the stress-strain curve when the tensile test is performed on the test piece in the +45° direction or in the -45° direction, and respectively the longitudinal and transverse strain at the mth measurement point when the tensile test is performed on the test piece in the 0° or 90° direction, respectively the load at the mth measurement point when the tensile test is performed on the test piece in the 0° or 90° direction, and respectively the longitudinal and transverse strain at the nth measurement point when the tensile test is performed on the test piece in the +45° or -45° direction, respectively the load at the nth measurement point when the tensile test is performed on the test piece in the +45° or -45° direction, the initial cross-sectional area of the test piece in the 0° or 90° direction, the initial cross-sectional area of the test piece in the +45° or -45° direction.

[0049] By the above equations, the shear modulus of the twill fabric composite material along the yarn direction and the stress-strain curve of the shear response (the abscissa of the nth point is and the ordinate is ) can be obtained, and the shear modulus of the twill fabric composite material along the axis direction at an angle of 45° with the yarn and the stress-strain curve of the shear response (the abscissa of the mth point is and the ordinate is ) can be calculated. To avoid contingency, the test can be performed on the test piece of the same type for multiple times, and the average value of the test results of each group is taken.

[0050] The principles and implementation manners of the present application are described by specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the field, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A method for measuring the shear modulus of two-dimensional woven composite materials based on uniaxial tensile testing, characterized in that, include: Step 1: Select plain weave, twill weave, or satin weave fabric to prepare a unidirectional lay-up two-dimensional woven fabric reinforced composite laminate. Cut the prepared unidirectional lay-up two-dimensional woven fabric reinforced composite laminate into multiple test pieces. The cutting direction is parallel to or at an angle of ±45° to the warp and weft directions of the two-dimensional woven fabric reinforced composite material. Step 2: Select test specimens parallel to the yarn direction and test specimens at an angle of ±45° to the yarn direction for tensile loading tests, and record the test data. Step 3: Combining the data from Step 2, obtain the shear mechanical properties of the fabric-reinforced composite material on the plane of the test specimen along the warp and weft directions and along directions with an angle of ±45° with the warp and weft directions.

2. The method for measuring the shear modulus of two-dimensional woven fabric reinforced composite materials according to claim 1, characterized in that, The unidirectional lay-up two-dimensional woven fabric reinforced composite laminate is cut into two types of test pieces, with the cutting directions of the test pieces being 0° / 90° and ±45° to the yarn direction of the two-dimensional woven fabric reinforced composite warp, respectively.

3. The method for measuring the shear modulus of two-dimensional woven fabric reinforced composite materials according to claim 1, characterized in that, For the test specimen in the 0° / 90° direction, the cross-sectional area of ​​the test specimen is... When performing a tensile test on it, the load at the m-th data point is The longitudinal normal strain of the m-th data point is The transverse normal strain of the m-th data point is The tensile modulus measured in the elastic region of the stress-strain line is: Poisson's ratio is .

4. The method for measuring the shear modulus of two-dimensional woven fabric reinforced composite materials according to claim 1, characterized in that, For the test specimen in the ±45° direction, the cross-sectional area of ​​the test specimen is... When performing a tensile test on it, the load at the nth data point is The longitudinal normal strain of the nth data point is The transverse normal strain of the nth data point is The tensile modulus measured in the elastic region of the stress-strain line is: Poisson's ratio is .

5. [Revised according to Rule 26, 04.07.2025] The method for measuring the shear modulus of two-dimensional woven fabric reinforced composite materials according to claim 3 is characterized in that, The shear modulus of the material in the direction within ±45° of the yarn direction of the two-dimensional woven fabric reinforced composite material The calculation method is as follows: .

6. [Amended according to Rule 26, 04.07.2025] The method for measuring the shear modulus of two-dimensional woven fabric reinforced composite materials according to claim 4 is characterized in that, The shear modulus of the material in the direction parallel to the yarn direction of the two-dimensional woven fabric reinforced composite material The calculation method is as follows: 。 7. The method for measuring the shear modulus of two-dimensional woven fabric reinforced composite materials according to claim 3, characterized in that, When a two-dimensional woven fabric reinforced composite material is subjected to shear along a direction with an angle of ±45° to the warp and weft yarns, the abscissa of the m-th data point on the shear stress-strain curve in that direction is: The ordinate of the m-th data point on the shear stress-strain curve in this direction is... .

8. The method for measuring the shear modulus of two-dimensional woven fabric reinforced composite materials according to claim 4, characterized in that, When a two-dimensional woven fabric reinforced composite material is subjected to shear along the warp and weft directions, the abscissa of the nth data point on the shear stress-strain curve in that direction is: The ordinate of the nth data point on the shear stress-strain curve in this direction is... .

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