A constant-life model of fatigue behaviour for carbon-fibre composites: The effect of impact damage

Following earlier,work on the development of a life-prediction method for four types of carbon-fibre composites subjected to constant-stress fatigue, we now attempt to assess the validity, of the method for composites which have sustained damage front low-velocity impacts. This parr of the work was carried out oil a fifth carbon-fibre composite, HTA/982A, having the same structure, a [(+/-45,O-2)(2)](s) lay-up, as those previously investigated. Replicate stress/life data were obtained at four stress ratios (R) of +-0.1, -0.3, -1.5 and + 10 on virgin samples and on samples damaged by a falling weight delivering 1 J of energy,. The constant-life model is shown to be valid for the undamaged laminate and is also able to account for the effects of the impact damage in reducing the compression strength and consequent compressive fatigue response of the material. (C) 1998 Elsevier Science Ltd. All rights reserved.