Analysis of Mechanical Properties of T700 Carbon Fiber Composite Material
Carbon fiber is a new type of carbon material that emerged in the 1960s. It has the advantages of high-temperature resistance, corrosion resistance, small thermal expansion coefficient, good dimensional stability, high specific strength, and high specific modulus. It is an ideal functional and structural material. The initial development field is the aerospace industry and military products, but now the application field is expanding very fast and has a good application prospect.
Japan's Toray, Toho, and Mitsubishi's three major groups have almost taken over the manufacture of small tow carbon fibers. In this paper, the basic mechanical properties of the unidirectional fiber composite sheet (referred to as unidirectional sheet) made of the same two high-performance T700 carbon fibers produced by Toray (TORAY) and Toho (TOHO) are tested, and the other Performance comparison data. Theoretical analysis of the data resulting in differences is provided for the reference selection of technicians who use this type of fiber in products.
According to the relevant international standards, the test specimens were produced and tested. The TORAY-T700 unidirectional plate sample first made a slight sound when it was close to the failure value of about 10%; while the TOHO-T700 unidirectional plate sample first made a slight sound when it was When it is close to about 20% of the damage value. However, loads of the two groups of samples did not fall, until the samples were destroyed with a violent sound, and the load value dropped rapidly. The 0° tensile strength of the TORAY-T700 unidirectional sheet is 1830.7MPa, and the 0° tensile modulus is 99.2GPa; while the corresponding parameters of the TOHO-T700 unidirectional sheet are 1690.7MPa and 109.3GPa. The resin content of the former is 37.1%, and that of the latter is 35.4%.
Through testing its compression performance, it can be seen that the 0° compressive strength of TORAY-T700 unidirectional plate is 895MPa, the compressive modulus is 97.9GPa, the 90° compressive strength is 125.4MPa, and the compressive modulus is 7GPa. The 0° compression strength of the TOHO-T700 unidirectional plate is 889.7MPa, the compression modulus is 105.4GPa, the 90° compression strength is 122.6GPa, and the compression modulus is 7.9GPa. The test results show that the two fibers have similar compressive capacity.
In addition, the interfacial properties of fibers and matrix are important parameters affecting the performance of composite materials. If it is weak, the reinforcement cannot do its job, and the result is a reduction in the strength of the composite. If it is strong, the damage resistance of the composite material is weak, and the result is a decrease in fracture toughness. In the design of composite material products, more attention is paid to the interface performance. Usually, the strength, thickness, and stress of the interface layer should be considered in the design. In this paper, the interfacial properties of the two fibers are investigated through the general transverse tensile properties and interlaminar shear properties of composite materials.
The transverse tensile test method to investigate the performance of the composite material matrix, and the commonly used short beam shear test method to measure the interlaminar shear strength, the specimen will inevitably produce interlaminar stress and strain, such as free edges and thickness changes. When the stress in the thickness direction of the specimen exceeds its strength value, spalling will occur. According to the test, the 90° tensile strength of the TORAY-T700 unidirectional plate is 31.3MPa, the 90° tensile modulus is 7.4GPa, and the interlaminar shear strength is 71.9MPa; the 90° tensile strength of TOHO-T700 unidirectional plate The strength is 31.3MPa, the 90° tensile modulus is 7.8GPa, and the interlaminar shear strength is 67.9MPa.
Through the above test and analysis results, we can know that compared with TOHO-T700 carbon fiber, TORAY-T700 carbon fiber is a more suitable reinforcement material for products with higher requirements for longitudinal stretch. The reason for the poor tensile strength of TOHOT-700 carbon fiber may come from the fiber itself and many hidden defects. The compressive properties of the unidirectional plate and the interfacial properties of the unidirectional plate layers were compared with the TORAY and TOHO T700 carbon fibers by the standard method, and the compressive properties and interface properties of the two were similar.