Acoustic Detection Technology For Tensile Damage Of Composite Materials In Hygrothermal Environment

Carbon fiber reinforced epoxy resin matrix composites(CFRP)were widely used in aerospace,marine,automotive and medical fields due to their excellent properties such as high temperature resistance,fatigue resistance and low specific gravity.However,its long-term exposure to hygrothermal environment is easy to cause aging and lead to the decline of mechanical properties,in which the stress field caused by hygrothermal environment is an important factor.In this paper,the moisture absorption behavior and failure mechanism of CFRP composites in hygrothermal environment were studied by the combination of finite element simulation and experimental research,which provides a technology for strength evaluation and life prediction of CFRP composites in service process.In this paper,by comparing and analyzing the influence of ambient temperature on the mechanical properties of composite specimens with the same ply thickness in different hygrothermal environments,and the influence of the characteristics of materials on their mechanical properties in the same hygrothermal environment,the hygroscopic kinetic curve was obtained,and the parameters of finite element simulation were determined.According to the convective heat transfer coefficient of the composite with air and water,the temperature change of the composite with time under dry and humid conditions was simulated by using the heat conduction module of ABAQUS.The parameters such as mass diffusion coefficient,saturated moisture absorption and solubility obtained from the hygroscopic kinetic curve were input into the mass diffusion module of ABAQUS,and the concentration field of the composites at different time and temperature was analyzed and studied.The tensile test,acoustic emission monitoring and material failure acoustic emission signal analysis methods of materials in different environments were studied respectively.It is concluded that the bearing capacity of composite fibers after moisture absorption is lower than that in room temperature environment.After the fiber breaks,the bearing capacity decreases sharply and the material quickly invalid research conclusions.The research results provide technical support for the design and application of carbon fiber composite structures working in hygrothermal environment.