Tension-tension fatigue behaviour of knitted fabric composites

The tension-tension fatigue behaviour of knitted fabric composites has been investigated. The fatigue damage of knitted fabric composites such as matrix cracks and yarn-matrix debonds was initiated from the part of the knitting loop that is perpendicular to the loading direction. The fatigue damage then propagated following the knitting structure. The fatigue properties of weft knitted fabric composites are compared with the fatigue properties of woven fabric composites, loaded in weft and bias (45degrees) directions. The residual mechanical properties after a certain number of fatigue cycles, such as stiffness and strength, are also presented. As the fatigue damage of the knitted fabric and woven fabric composites in the bias direction is matrix dominated, the hysteresis heating is studied by varying the fatigue frequency. (C) 2003 Elsevier Ltd. All rights reserved.