MICROSCOPIC FATIGUE PROCESSES IN A PLAIN-WEAVE GLASS-FIBER COMPOSITE

This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and 'meta-delaminations' between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a 'meta-CDS) was observed. It was found that woven composites have a unit area of damage accumulation (called a 'unit cell') and the damage of each unit cell and its distribution control the total fatigue damage of the material.