Finite Element Analyses Of Bending Fatigue Behaviors Of Three-dimensional Angle-interlock Woven Composite With Full-scale Structure Model

As one kind of three-dimensional textile composites, three-dimensional angle-interlock woven composites (3DAWCs) can be produced with low cost and high efficiency. And they have good mechanical performances such as resistance of delamination, high impact-resistance, relatively high stiffness and strength in thickness direction. Besides, it is possible to produce engineering structures with complex shapes. It is inevitable that engineering structure material will undertake fatigue loading during use. The fatigue damage accumulation may lead to sudden breakage of the material, which always happens without warning. So it is quite important to study the fatigue behaviors of3DAWC. In this paper, a full-scale geometry structure model of3DAWC was built and the fatigue damage criterion was introduced. After the calculation, the experiment was used to demonstrate the validity of the full-scale geometry structure model. The bending fatigue damage mechanism was revealed based on the combination of experiment and finite element calculation.The large-scale geometric solid model on microstructure level was built in accordance with the real structure of layer-to-layer3DAWC. Based on inelastic hysteresis energy fatigue damage criterion, finite element fatigue damage model was built to calculate the stress distribution, deformation, energy absorption and stiffness degradation and reveal the characteristics of stress distribution and deformation, and analyze the role of each component during the process of fatigue. Based on the interface crack initiation and propagation theory, finite element fatigue model that contained interface crack was established to make a detailed understanding of the process of material damage and crack propagation. And the damage mechanism and structural effect on fatigue behaviors were analyzed from test result and finite element calculation result. We can conclude as:(1) The stress concentration of the whole model mainly focus on the top and bottom parts of center load-carrying area, in more detail, the inclined parts of warp yarns and the interface between yarns and resin;(2) Material damage mainly occurred on warp yarns and resin. And for a single warp yarn,the damage was on the inclined parts and the buckling parts. For resin, the damage appeared on the interface of resin and yarns;(3) The crack propagated both from thickness direction and longitudinal direction. And during the process of fatigue, crack and material damage interacted;(4) Both the test result and FEA result showed three stages of the stiffness degradation:the mechanical property sharply decreased for a short time, then it came to the smooth stage. At the third stage, the material was decreased more sharply than the first stage until the breakage happened.The research in this paper reveals the bending fatigue damage mechanism of3DAWC and can be a reference and support for anti-fatigue structure design of three-dimensional woven composites and other three-dimensional textile composite materials.