Multiscale modeling of mechanical behaviors of carbon fiber reinforced epoxy composites subjected to hygrothermal aging

This paper investigates the hygrothermal aging behaviors including the aging law, the moisture absorption, and residual stresses for carbon fiber reinforced epoxy composites via the multiscale finite element method (FEM). Based on the disturbance and the collision algorithm, a microscale unit cell is established with random fibers, interface and matrix. Component mechanical properties are evaluated by an exponential function of temperature and moisture absorption. Furthermore, we propose a defect hypothesis to generate hygrothermal aging defects. The specimen-sized laminate model is established with intralaminar elements and interlaminar elements, which introduces three-dimensional (3D) strain-form Hashin criteria and an improved traction separation cohesive law, respectively. The quantitative characterization for the hygrothermal aging is well obtained by the genetic algorithm, and good agreement, in terms of mechanical properties and failure modes, is observed between experimental and numerical results. Compared with semi-empirical methods, the multi scale model could reveal the relationship between the microscale structure evolution and the macroscale property degradation. Conclusively, the severer hygrothermal aging environment would accompany with less matrix attached to fibers. After 9 severest accelerated hygrothermal aging cycles, the transverse modulus, the transverse tensile strength, the transverse compression strength and the interlaminar shear strength could drop more than 36%, 38%, 58% and 25%, respectively.

Automated summary

This study investigates the hygrothermal aging behaviors of carbon fiber reinforced epoxy composites using a multiscale finite element method, and proposes a defect hypothesis to explain the generation of aging defects. Good agreement between experimental and numerical results is observed, showing the impact of hygrothermal aging on the mechanical properties of the composites.