Composite material II-type interlayer fracture toughness measuring device for obtaining complete R curve

Abstract

The invention relates to a composite material II-type interlayer fracture toughness measuring device for obtaining a complete R curve, which is suitable for a tensile load device to carry out fracture toughness test on a test piece made of a polymer matrix composite material, and comprises a base, a support plate arranged in a special-shaped I-shaped structure, a loading lug plug, a support table and an adjusting plate, the supporting plate is detachably installed on the top face of the base, the adjusting plate is installed on the top face of the supporting plate in a horizontal sliding mode, the supporting table is fixedly installed on the top face of the adjusting plate, the small end of the loading lug plug is connected with the output end of the tension load device, and the large end of the loading lug plug fixes one end of a test piece in a pin hole matching mode. And the other end of the test piece is mounted on the trapezoidal part of the supporting table, so that the test efficiency is improved, and a complete II-type interlayer fracture toughness curve of the composite material is obtained.

Description

Technical Field

[0001] This invention belongs to the technical field of composite material performance testing devices, and particularly relates to a composite material type II interlaminar fracture toughness measuring device for obtaining a complete R-curve. Background Technology

[0002] Polymer-based composites possess advantages such as high specific strength, high specific stiffness, high designability, and fatigue resistance, and are widely used in the manufacture of parts in the aerospace field. In modern civil aircraft design, to meet weight reduction requirements, the application of composite materials is increasingly prevalent. Damage modes mainly include four types: matrix cracking, fiber fracture, fiber-matrix debonding, and delamination. Delamination is the most common failure mode, and Type II delamination toughness is one of the important criteria for screening high-density delamination-resistant carbon fiber composites and a key input parameter for composite strength analysis. When composites are subjected to out-of-plane impact, delamination propagation is mainly dominated by Type II delamination toughness. Therefore, accurately determining the Type II delamination toughness of composite materials is of great significance for material research and development, material screening, quality control, material specification formulation, structural design, and strength verification.

[0003] Previously, domestic testing methods for the type II interlaminar fracture toughness of polymer-based composite materials referenced ASTM D7905 and HB 7403. Both methods employed a three-point bending test, which could only obtain the type II interlaminar fracture toughness value at a certain delamination length, but could not obtain the type II interlaminar fracture toughness value at any crack length. In other words, it could not obtain a complete R-curve of the type II interlaminar fracture toughness of the material.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The present invention provides a composite material type II interlaminar fracture toughness measurement device for obtaining a complete R-curve. When testing the type II interlaminar fracture toughness of polymer-based composite materials, this device can obtain a complete R-curve of the material's type II interlaminar fracture toughness, thereby improving the efficiency of performance testing. The technical solution of this invention has many beneficial effects, as described below: A type II interlaminar fracture toughness measuring device for obtaining a complete R-curve of composite materials is disclosed. This device is suitable for performing fracture toughness tests on polymer-based composite material specimens using a tensile loading device. The specimens have cracks of a preset length. The device includes a base, a support plate with an irregularly shaped I-beam structure, a loading lug, a support platform, and an adjustment plate. The support plate is detachably mounted on the top surface of the base, the adjustment plate is horizontally slidably mounted on the top surface of the support plate, and the support platform is fixedly mounted on the top surface of the adjustment plate. The small end of the loading ear plug is connected to the output end of the tensile load device, and the large end is fixed to one end of the test piece by means of a pin hole. The other end of the test piece is installed on the trapezoidal part of the support platform.

[0006] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: This structure can obtain a complete R-curve of the type II interlaminar fracture toughness of polymer-based composite materials. At the same time, by adjusting the relative position of the adjustment plate and the support plate, it can adapt to the test of different parts. During the loading process, as the test piece deforms, it can ensure that the direction of the loading force remains perpendicular, and the obtained complete R-curve of the type II interlaminar fracture toughness of polymer-based composite materials has higher accuracy. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a perspective view of the device of the present invention from a first-view perspective; Figure 2 This is a perspective view of the device of the present invention from a second viewpoint; Figure 3 This is a schematic diagram of the loading block; Figure 4 This is a schematic diagram of the support platform; Figure 5 This is a schematic diagram of the slide block, where, 1. Loading earplug; 2. Test piece; 3. Loading block; 5. Fixing pressure plate; 6. Limiting strip; 7. Support platform; 8. Adjusting plate; 9. Slide rail block; 10. Steel ball; 11. Support plate; 12. Base; 13. Through groove. Detailed Implementation

[0009] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0010] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0011] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0012] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that aspects can be practiced without these specific details. To enable those skilled in the art to better understand the invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of that feature. In the description of the invention, unless otherwise stated, "a plurality of" means two or more.

[0013] like Figures 1 to 5The composite material type II interlaminar fracture toughness measuring device shown is suitable for fracture toughness testing of polymer-based composite material test specimens using a tensile load device. The test specimen has a crack of a preset length and includes a base 12, a support plate 11 with an irregular I-shaped structure, a loading ear plug 1, a support platform 7, and an adjusting plate 8. The support plate 11 is detachably mounted on the top surface of the base 12, and the adjusting plate 8 is mounted on the top surface of the support plate 11 in a horizontal sliding manner. The support platform 7 is fixedly mounted on the top surface of the adjusting plate 8. The small end of the loading ear plug 1 is connected to the output end of the tensile load device, and the large end is fixed to one end of the test specimen by a pin hole (e.g., one end of the test specimen is placed in the loading block 3, and the loading block 3 and the large end of the loading ear plug 1 are fixed by a pin). The other end of the test specimen is mounted on the trapezoidal part of the support platform 7.

[0014] Working principle: During the test, the tensile load device generates a vertical tensile force and applies it to the loading lug 1. Under the force of the loading lug 1, the test piece is driven to bend and deform. The adjusting plate 8 can move or slide along the centerline direction of the test piece in its initial state, so that the loading lug 1 continuously generates a vertical tensile force on the test piece. The camera device set on the tensile load device continuously collects the crack state change data and feeds it back to the tensile load device. The tensile load device generates a type II interlaminar fracture toughness curve under the crack length of the test piece based on the real-time loaded tensile force and state change data.

[0015] In one embodiment, the width of the bottom end of the support plate 11 is greater than the width of the top end, and the length of the top end is greater than the length of the bottom end. The numerical part of the support plate 11 is set in an inclined manner, which can both meet the needs of the sliding distance of the adjustment plate 8 and facilitate the installation of the bottom end of the support plate 11 on the top surface of the base 12.

[0016] In one embodiment, the adjusting plate 8 is slidably mounted on the top of the support plate 11 via a slide rail block 9. Specifically, a through groove 13 is formed on one side of the slide rail block 9 along its length, and a recess is formed at the bottom end of the through groove 13. A rolling steel ball 10 is placed in the recess, and the steel ball 10 slidably supports the bottom surface of the adjusting plate 8, while the top surface of the adjusting plate 8 does not contact the top end of the through groove 13. After the slide block 9 engages with both sides of the top surface of the support plate 11 through the through groove 13, the key adjustment plate 8 is fixed to the top surface of the slide block 9 by bolts. When the loading ear plug 1 applies a tensile force to the test piece in the vertical direction, the adjustment plate 8 slides relative to the top of the support plate 11 through the ball bearings to ensure that the tensile force of the loading ear plug 1 is always in a vertical state.

[0017] In one embodiment, the adjusting plate 8 is provided with mounting holes at intervals at one end adjacent to the loading ear plug 1. The mounting position of the support platform 7 relative to the adjusting plate 8 is adjusted through the mounting holes to accommodate the fixing of test pieces of different specifications. Preferably, the end of the support platform 7 away from the loading ear plug 1 is provided with a trapezoidal part, which is a trapezoidal block. The trapezoidal block and the support platform 7 are integrally structured, and the other end of the test piece is fixedly installed through the top of the trapezoidal block.

[0018] Furthermore, it also includes a fixing plate 5, which clamps the other end of the test piece with the top surface of the trapezoidal block and is fastened with screws. Preferably, the trapezoidal block has a hole on its axially upward side away from the loading ear 1, and a limiting strip 6 is installed in the hole. The limiting strip 6 is used for aligning or centering the test piece. It can obtain the complete correspondence between the crack length of the test piece 2 and the applied load and displacement in real time, and further obtain the R curve of the material's type II interlaminar fracture toughness.

[0019] The specific implementation steps include: (1). First step: Fix the support plate to the loading platform with bolts; (2). Second step: Bond the pre-cracked end of the test specimen to the loading block; (3) Third step: Adjust the loading arm length, fix the test piece between the fixed pressure plate and the fixed support plate with bolts, and ensure the loading center of the test piece by adjusting the limit strip; (4) Fourth step: Connect the adjusting plate, the support plate and the slide groove together with bolts; (5) Step 5: Place the steel ball into the groove so that the steel ball contacts the support plate; (6) Step 6: Connect the loading earplug to the loading block using a pin; (7) Step 7: Apply tensile load, obtain the relationship between crack length of test piece and load and displacement, and further obtain the R curve of type II interlaminar fracture toughness of material.

[0020] The product provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the invention claims.

Claims

1. A type II interlaminar fracture toughness measuring device for obtaining a complete R-curve of composite materials, suitable for performing fracture toughness tests on polymer-based composite material specimens using a tensile loading device, wherein the specimens have cracks of a preset length, characterized in that... Includes a base, a support plate with an irregular I-beam structure, a loading earpiece, a support platform, and an adjustment plate, among which, The support plate is detachably mounted on the top surface of the base, the adjustment plate is horizontally slidably mounted on the top surface of the support plate, and the support platform is fixedly mounted on the top surface of the adjustment plate. The small end of the loading ear plug is connected to the output end of the tensile load device, and the large end is fixed to one end of the test piece by means of a pin hole. The other end of the test piece is installed on the trapezoidal part of the support platform.

2. The composite material type II interlaminar fracture toughness measuring device according to claim 1, characterized in that, The bottom of the support plate is wider than the top, and the top is longer than the bottom. The numerical part of the support plate is set at an angle.

3. The composite material type II interlaminar fracture toughness measuring device according to claim 1, characterized in that, The adjusting plate is slidably mounted on the top of the support plate via a slide rail block. A through groove is provided on one side of the slide block along its length, and a groove is provided at the bottom end of the through groove. A rolling steel ball is placed in the groove. The steel ball supports the bottom surface of the adjustment plate in a sliding manner, and the top surface of the adjustment plate does not contact the top end of the through groove. After the slide blocks are respectively engaged with the top surfaces of the support plate by the through slots, the key adjustment plate is fixed to the top surface of the slide blocks by bolts. When the loading ear plug applies a tensile force to the test piece in the vertical direction, the adjustment plate slides relative to the top of the support plate through the ball bearings to ensure that the tensile force of the loading ear plug is always in a vertical state.

4. The composite material type II interlaminar fracture toughness measuring device according to claim 1, characterized in that, The adjustment plate has mounting holes spaced apart at one end adjacent to the loading earpiece. The position of the support platform relative to the adjustment plate can be adjusted through the mounting holes to accommodate the fixing of test pieces of different specifications.

5. The composite material type II interlaminar fracture toughness measuring device according to claim 1, characterized in that, The trapezoidal part is provided at the end of the support platform away from the loading earpiece. The trapezoidal part is a trapezoidal block. The trapezoidal block is integrally formed with the support platform. The other end of the test piece is fixedly installed through the top of the trapezoidal block.

6. The composite material type II interlaminar fracture toughness measuring device according to claim 5, characterized in that, It also includes a fixed pressure plate, which clamps the other end of the test piece with the top surface of the trapezoidal block and is fastened with screws.

7. The composite material type II interlaminar fracture toughness measuring device according to claim 6, characterized in that, The trapezoidal block has a hole on its axially upward side away from the loading earpiece, and a limiting strip is installed in the hole. The limiting strip is used for aligning or centering the test piece.

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