The NDT Technology For Impact Damage Of Carbon Fiber Reinforced Resin Matrix Composite

With the advantages of light weight and high strength, advanced composites material has been widely used in modern aerospace fields. The laminated composite structures are more sensitive to impact, even under the low-energy impact, there is no trace on the structure surface, the inner structure may appear serious stratified, matrix crack and fiber breakage etc, leading mechanical properties such as compression strength to be decreased greatly.According to "the general technical specifications of HB72242-95composite structures" and "the general specification of GJB28952-97carbon fiber composite laminates", the impact specimens which are called T300/QY8911are designed. The length of the laminates is250mm, the width is180mm, and the width of each layer is0.12mm. Free fall impact test simulates low-energy impact such as the hail, runway gravel impact, the impact of ordinary tools, and human stampede etc, and the impact damage samples under different impact energy were obtained. In the paper, explicit finite element method, three-dimensional Tsai-Wu failure criterion and material stiffness criteria for conversion were used, to simulate the impact damage process of the laminates. Based on the study of the ultrasonic C scan and the laser shearography test parameters, the impact damage of different energy on carbon fiber reinforced composites are detected.The results show that the composite structure under low-energy impact, the surface has no hit, but the inner damage has been detected. With the impact energy increases, drop mark appears on the surface, and the delamination appears in the lamination. When the impact energy reaches a certain value, the fiber breakage appears on the sample surface, and the matrix crack is parallel to the fiber direction. The results of Finite element simulation are consistent with those of the ultrasonic C scan test. The results of the thermal shearography are poorer than the vacuum shearography. When the energy reaches more than5J, the impact damage area can be obtained by the ultrasonic C scan test. when the impact energy reaches more than23J, the results of the thermal shearography test is similar to those of the ultrasonic C scan test. Explicit finite element model,three-dimensional Tsai-Wu failure criterion for damage and material stiffness criteria for conversion are proved by the results in the paper.In the paper, Impact damage and prediction can be obtained by finite element method, the ultrasonic C scan test and the thermal shearography test both can be used to detect the impact damage. The nondestructive testing parameters in the paper not only make the manufacturing process improved, and the time limit extended, but also provide the basis for the patch program of the composite laminates under low-velocity impact.