Thermal-mechanical coupling tensile test method for structure and function integrated composite material
By incorporating resistance wire heating and using a U-shaped clamp design, the problems of stress concentration and low thermal efficiency in tensile tests of structurally functional composite materials are solved, enabling a realistic simulation and accurate evaluation of thermo-mechanical coupling performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-14
AI Technical Summary
Existing technologies suffer from stress concentration and low thermal efficiency when conducting tensile tests on structurally functional composite materials, leading to distorted test results and making it difficult to accurately assess their thermo-mechanical coupling performance under real service conditions.
Thermocouple loading is achieved by using built-in resistance wire heating, and a U-shaped clamp is used to form a clamping end with the laminate to avoid stress concentration, ensure uniform loading and internal simulation of the heat source.
This method enables a realistic simulation of structurally functional composite materials under actual working conditions, ensuring the accuracy and validity of test results, eliminating the risk of stress concentration, and improving the reliability of the test.
Smart Images
Figure CN121856015A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of aerospace structural strength testing technology, and specifically relates to a thermo-mechanical coupling tensile testing method for structurally functional integrated composite materials. Background Technology
[0002] In the development of modern aerospace equipment, structurally functional composite materials have been increasingly widely used due to their multiple functional properties, including load-bearing, thermal insulation, wave transmission, and lightning protection. These structures typically employ a sandwich configuration, consisting of upper and lower panels and a central functional module area (such as thermal insulation core material and functional circuitry). To accurately evaluate their mechanical properties under real-world service conditions, especially their load-bearing capacity under thermal conditions, thermo-mechanical coupling strength tests must be conducted, i.e., simultaneously applying in-plane tensile and thermal loads to the test specimen.
[0003] Currently, the conventional testing method for tensile tests on this type of structure mainly involves directly clamping the specimen to the support end face using fixtures. However, this traditional method reveals the following significant technical defects and limitations when dealing with structurally functional composite materials, especially when the overall thickness of the specimen is thin or the structure is complex:
[0004] Because structurally and functionally integrated composite materials typically cannot uniformly transfer loads in the clamping area using traditional bolt connections or other fastening methods, end-face clamping inevitably leads to severe stress concentration. When the test specimen is thin, this stress concentration can easily cause unacceptable failure modes at the support end, such as support end slippage, end bending, or crushing. These failure modes are not actual failures in the test area of the specimen, but are caused by improper support methods, severely interfering with the accurate assessment of the material's thermo-mechanical coupling properties, resulting in invalid or distorted test results.
[0005] Traditional thermal testing typically uses external heating devices, such as hot air guns, infrared heating lamps, and high-temperature furnaces, to heat the surface of the test piece. This method suffers from problems such as low thermal efficiency, uneven temperature field, and severe thermal hysteresis, making it difficult to accurately simulate the real working conditions where there are heat sources inside the structure, and failing to realize the true coupling environment between internal heat sources and tensile loads. Summary of the Invention
[0006] To address the aforementioned problems, this application provides a thermo-mechanically coupled tensile testing method for structurally functional integrated composite materials, mainly comprising:
[0007] Prepare a test specimen, the test specimen including a test specimen assessment area in the middle and clamping ends located at both ends of the test specimen assessment area along the loading direction; the test specimen assessment area includes an upper composite material panel, a lower composite material panel and a functional module area located therebetween, a functional module is arranged in the functional module area, a resistance wire is wound on the functional module, and the two ends of the resistance wire are led out to the outside of the test specimen;
[0008] The clamping ends at both ends of the test piece are respectively connected to a U-shaped test fixture by fasteners;
[0009] Install the two U-shaped test fixtures onto the chucks of the testing machine;
[0010] A pair of in-plane, opposite tensile loads are applied to the test piece using the testing machine.
[0011] Simultaneously, the two ends of the resistance wire are connected to a power source, causing the resistance wire to heat up, thereby introducing a heat source into the test piece and achieving thermo-mechanical coupling loading.
[0012] Preferably, the preparation process of the test specimen includes:
[0013] The upper composite material panel, the lower composite material panel, and the middle functional module area containing the functional module are bonded together with core adhesive to form the structure.
[0014] Along the direction of the applied load on the test piece, the upper composite material panel and the lower composite material panel are extended outward, and the clamping end is formed by a laminate laying process.
[0015] Preferably, in the functional module area, the functional modules are evenly arranged in a matrix, the gaps between the functional modules are filled with expanding foam, and the two ends of the resistance wire are led out through the expanding foam.
[0016] Preferably, the limit value F of the tensile load is designed according to the following formula:
[0017] ;
[0018] in, , These are the equivalent moduli of the upper composite panel and the lower composite panel along the tensile direction, respectively. For the allowable tensile strain of the composite panel, , These are the widths of the loading edges of the upper and lower composite material panels, respectively. , These are the thicknesses of the upper composite panel and the lower composite panel, respectively.
[0019] Preferably, the length L of the resistance wire is determined in the following way:
[0020] ;
[0021] Where R is the total resistance of the resistance wire. The resistance per unit length of the selected resistance wire, and the total resistance of the resistance wire, are determined by the following formula:
[0022] ;
[0023] U is the voltage of the test power supply, and P is the power of the test power supply.
[0024] Preferably, the method further includes a measurement step:
[0025] Strain gauges are arranged at the intersections of multiple transverse and longitudinal sections in the test area of the test specimen, and the strain gauges are symmetrically arranged on both the front and back sides of the test specimen.
[0026] During the test, the alignment and repeatability of the load were checked using the strain gauge measurement data, and the measured strain values were obtained.
[0027] This application eliminates the risk of stress concentration at the support end and achieves realistic simulation of internal heat source-load coupling. Attached Figure Description
[0028] Figure 1 This is a top view of a test specimen according to a preferred embodiment of the thermo-mechanical coupling tensile testing method for structurally functional integrated composite materials of this application.
[0029] Figure 2 This is a side view of the test specimen.
[0030] Figure 3 This is a schematic diagram of the interior of the test specimen.
[0031] Figure 4 This is a schematic diagram showing the connection between the test piece and the test fixture.
[0032] Figure 5 This is a schematic diagram of the experimental measurement.
[0033] Among them, 1-test area, 2-clamping end, 3-functional module, 4-foaming adhesive, 5-resistance wire, 6-test fixture, 7-strain gauge. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.
[0035] This application provides a thermo-mechanically coupled tensile testing method for structurally functional integrated composite materials, mainly including:
[0036] Prepare a test specimen, the test specimen including a test specimen assessment area 1 in the middle and clamping ends 2 located at both ends of the test specimen assessment area along the loading direction; the test specimen assessment area includes an upper composite material panel, a lower composite material panel and a functional module area located therebetween, a functional module 3 is arranged in the functional module area, a resistance wire 5 is wound on the functional module, and the two ends of the resistance wire are led out to the outside of the test specimen.
[0037] The clamping ends at both ends of the test piece are respectively connected to a U-shaped test fixture 6 by fasteners;
[0038] Install the two U-shaped test fixtures onto the chucks of the testing machine;
[0039] A pair of in-plane, opposite tensile loads are applied to the test piece using the testing machine.
[0040] Simultaneously, the two ends of the resistance wire are connected to a power source, causing the resistance wire to heat up, thereby introducing a heat source into the test piece and achieving thermo-mechanical coupling loading.
[0041] This application establishes a test method capable of realistically simulating the coupled effects of internal heat sources and tensile loads on structurally functional composite materials under actual working conditions. This method utilizes a unique test specimen design, such as... Figures 1-3 As shown, by embedding the heat source within the functional module area, heating from within the specimen is achieved. Compared to traditional external heating methods, this more realistically simulates actual thermal environments such as those experienced by electronic devices. Furthermore, as... Figure 4 As shown, the force is transmitted by connecting the U-shaped clamp to the clamping end formed by the laminate, which effectively avoids the stress concentration problem caused by conventional end-face clamping methods, ensuring that the failure occurs in the test area rather than the support end, thereby guaranteeing the accuracy and validity of the test results.
[0042] In some alternative embodiments, the preparation process of the test specimen includes:
[0043] The upper composite material panel, the lower composite material panel, and the middle functional module area containing the functional module are bonded together with core adhesive to form the structure.
[0044] Along the direction of the applied load on the test piece, the upper composite material panel and the lower composite material panel are extended outward, and the clamping end is formed by a laminate laying process.
[0045] In this embodiment, the special design of the clamping end is key to solving the stress concentration problem. Specifically, after bonding the test area 1 (the upper and lower panels and the functional module area), the upper and lower composite material panels need to be extended outward along the load direction, and the extended part is reinforced and cured using a laminate laying process, thereby forming two solid laminate areas on the left and right as clamping ends 2. This design significantly increases the stiffness and strength of the clamping end in the thickness direction, enabling it to transfer the tensile load from the U-shaped clamp to the test area more evenly and stably through fasteners (such as bolts), fundamentally eliminating the risk of abnormal failures such as bending, crushing, or slippage that easily occur at the ends of thin-walled specimens.
[0046] In some alternative embodiments, in the functional module area, the functional modules are evenly arranged in a matrix, the gaps between the functional modules are filled with expanding foam, and the two ends of the resistance wire are led out through the expanding foam.
[0047] The detailed construction of the functional module areas ensures the feasibility and reliability of the internal heat source. The matrix arrangement of the functional modules 3 guarantees the regularity of the structure. The primary function of filling the gaps between the modules with expanding foam 4 is to fix and support the functional modules and the resistance wires 5 wound around them, forming a stable overall structure; secondly, the expanding foam 4 also provides some thermal insulation and electrical insulation. More importantly, it provides a protected lead-out path for the two ends of the resistance wires 5, ensuring that they can smoothly extend from the edge of the functional module and connect to an external power source, thereby successfully achieving internal heating. This construction makes the specimen itself a controllable "thermo-coupled" unit.
[0048] In some alternative embodiments, the limit value F of the tensile load is designed according to the following formula:
[0049] ;
[0050] in, , These are the equivalent moduli of the upper composite panel and the lower composite panel along the tensile direction, respectively. For the allowable tensile strain of the composite panel, , These are the widths of the loading edges of the upper and lower composite material panels, respectively. , These are the thicknesses of the upper composite panel and the lower composite panel, respectively.
[0051] By designing the load using the above formula, it can be ensured that the test is loaded to the expected level, mainly assessing the strength of the composite panel, while avoiding excessive and unintended mechanical damage to the functional module area.
[0052] In some alternative embodiments, the length L of the resistance wire is determined in the following way:
[0053] ;
[0054] Where R is the total resistance of the resistance wire. The resistance per unit length of the selected resistance wire, and the total resistance of the resistance wire, are determined by the following formula:
[0055] ;
[0056] U is the voltage of the test power supply, and P is the power of the test power supply.
[0057] Understandably, precise control of the internal heat source is crucial for achieving the desired thermal environment. The calculation process for the resistance wire length reflects the precise planning of the heating power. First, based on the voltage (U) of the available test power supply and the desired heating power (P), the required total resistance value (R) of the resistance wire is derived using the power formula. Then, based on the selected resistance wire specifications (whose resistance per unit length is a known parameter), the required precise length (L) is calculated. Finally, this length of resistance wire is uniformly wound around the functional module in multiple turns to generate a temperature field that is as uniform and stable as possible throughout the test area, meeting the test's requirements for thermal environment consistency.
[0058] In some alternative implementations, the method further includes a measurement step:
[0059] Strain gauges are arranged at the intersections of multiple transverse and longitudinal sections in the test area of the test specimen, and the strain gauges are symmetrically arranged on both the front and back sides of the test specimen.
[0060] During the test, the alignment and repeatability of the load were checked using the strain gauge measurement data, and the measured strain values were obtained.
[0061] like Figure 5As shown, strain gauges axx and bxx are arranged symmetrically back-to-back. This embodiment firstly, by comparing the strain values on both sides, can effectively monitor and evaluate whether bending occurs during the loading process (i.e., whether the alignment is good); secondly, it ensures the comprehensiveness and reliability of strain measurement, enabling the acquisition of detailed strain distribution data of the test area under multiaxial stress. These measured strain data are the most direct and important basis for analyzing the deformation behavior of materials under thermo-mechanical coupling, verifying simulation models, and studying their failure mechanisms.
[0062] The test specimen designed in this application effectively simulates the loading mode of a functional-structure integrated composite material structure under the coupled action of internal heat source and tensile load. It can be used to study and verify its failure mechanism and load-bearing capacity. The test specimen is simple to manufacture and easy to connect and install with fixtures and testing machines. It can eliminate the risk of unacceptable failure modes such as slippage, end bending, and crushing at the support end due to stress concentration in conventional testing methods. It realizes the experimental research and verification of thermo-mechanical coupled tensile testing of functional-structure integrated composite materials.
[0063] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A thermo-mechanically coupled tensile testing method for structurally functional integrated composite materials, characterized in that, Includes the following steps: Prepare a test specimen, the test specimen including a test specimen assessment area in the middle and clamping ends located at both ends of the test specimen assessment area along the loading direction; the test specimen assessment area includes an upper composite material panel, a lower composite material panel and a functional module area located therebetween, a functional module is arranged in the functional module area, a resistance wire is wound on the functional module, and the two ends of the resistance wire are led out to the outside of the test specimen; The clamping ends at both ends of the test piece are respectively connected to a U-shaped test fixture by fasteners; Install the two U-shaped test fixtures onto the chucks of the testing machine; A pair of in-plane, opposite tensile loads are applied to the test piece using the testing machine. Simultaneously, the two ends of the resistance wire are connected to a power source, causing the resistance wire to heat up, thereby introducing a heat source into the test piece and achieving thermo-mechanical coupling loading.
2. The thermo-coupled tensile testing method for structurally functional integrated composite materials as described in claim 1, characterized in that, The preparation process of the test specimen includes: The upper composite material panel, the lower composite material panel, and the intermediate functional module area containing the functional module are bonded together using core adhesive. Along the direction of the applied load on the test piece, the upper composite panel and the lower composite panel are extended outward, and the clamping end is formed by a laminate laying process.
3. The thermo-coupled tensile testing method for structurally functional integrated composite materials as described in claim 1, characterized in that, In the functional module area, the functional modules are evenly arranged in a matrix, and the gaps between the functional modules are filled with expanding foam. The two ends of the resistance wire are led out through the expanding foam.
4. The thermo-mechanically coupled tensile testing method for structurally functional integrated composite materials as described in claim 1, characterized in that, The limit value F of the tensile load is designed according to the following formula: ； in, , These are the equivalent moduli of the upper composite panel and the lower composite panel along the tensile direction, respectively. For the allowable tensile strain of the composite panel, , These are the widths of the loading edges of the upper and lower composite material panels, respectively. , These are the thicknesses of the upper composite panel and the lower composite panel, respectively.
5. The thermo-mechanically coupled tensile testing method for structurally functional integrated composite materials as described in claim 1, characterized in that, The length L of the resistance wire is determined by the following method: ； Where R is the total resistance of the resistance wire. The resistance per unit length of the selected resistance wire, and the total resistance of the resistance wire, are determined by the following formula: ； U is the voltage of the test power supply, and P is the power of the test power supply.
6. The thermo-mechanically coupled tensile testing method for structurally functional integrated composite materials as described in claim 1, characterized in that, The method further includes a measurement step: Strain gauges are arranged at the intersection of multiple transverse and longitudinal sections in the test area of the test specimen, and the strain gauges are symmetrically arranged on both the front and back sides of the test specimen. During the test, the alignment and repeatability of the load were checked using the strain gauge measurement data, and the measured strain values were obtained.