Implementation of progressive failure for fatigue based on cycle-dependent material property degradation model

Abstract

Anisotropic composite materials have been extensively utilized in mechanical, automotive, aerospace and other engineering areas due to high strength/weight ratio, superb resistance to corrosion and excellent thermos-mechanical properties. As the use of composite materials increases, determination of material properties, mechanical analysis and failure of the structure become essential for the design of composite structure. In particular, the fatigue failure is important to ensure that structures can survive in harsh environmental conditions. The non-homogeneous character of composites induces diverse failure modes of the constituent including fiber fracture, matrix cracking, fiber-matrix interface failure, and delamination, which makes their fatigue behavior very complex in comparison with traditional engineering materials. In this study, based on different failure modes of a unidirectional ply under multiaxial stress states, a progressive damage theory is extended to simulate fatigue failure in composite laminates subjected to cyclic loadings. A cycle-dependent material property degradation model was employed to predict deterioration of the material properties due to arbitrary stress state and ratio. This cycle-dependent material property degradation rule is implemented into user subroutine USDFLD in ABAQUS through which cycle-dependent material degradation states are updated over fatigue loading. The present computational implementation is tested by comparing the experimental fatigue behavior of a 30-degree off-axis specimen with the simulation result obtained by the present implantation. The comparison between the experimental and simulation results demonstrates the successful simulation capability of the present implementation.