Experimental Investigations And FEM Simulations On The Three-point Bending Fatigue Of 3D Orthogonal Woven Composite

As one of 3D woven composite,3D orthogonal woven composite (3DOWC) have higher strength and stiffness in the three direction because three are three different types of yarns namely stuffer yarns, filler yarns and z yarns in the fabric construction. These three types of yarns are placed in three mutually orthogonal direction. It is important to study the three point bending fatigue behavior of the 3DOWC because of the wide potential applications in engineering, especially in the design of engineering structural material for vehicles.This paper reports the three-point bending fatigue behavior of 3DOWC. The S-N curve was obtained to illustrate the relationship between applied stress levels and number of cycles to failure. The stiffness variation was recorded to show the degradation of mechanical properties of the 3DOWC during the process of fatigue loading. Furthermore, the fatigue damage morphologies of the tested 3DOWC coupons were given to indicate the damage modes of different parts (resin, yarns and their interface) of the composite under a range of stress levels. The damage distribution along the longitudinal direction of the composite coupon under the stress level of 60% was presented to illustrate the cumulative damage mechanisms of the 3DOWC under bending fatigue loading. In particular, a user material subroutine UMAT which characterizes the stiffness matrix and fatigue damage evolution of the 3DOWC was employed and incorporated with a finite element code ABAQUS/Standard to calculate the maximum deflection of composite during each cycle of bending fatigue loading. There were good agreements between experimental results and those obtained from finite element analysis (FEA).