Analysis of fatigue and damage in glass-fibre-reinforced polypropylene composite materials

This paper concerns fatigue studies of polypropylene/glass-fibre thermoplas tic composites produced from a bi-directional woven cloth of co-mingled E-g lass fibres and polypropylene fibres with a fibre volume fraction V-f of 0. 338. The effect of lay-up design and load conditions on fatigue performance were investigated. The S-N curves, the rise in the temperature of the spec imens, and the loss of stiffness during the tests, are discussed. Fatigue t ests were performed in controlled displacement mode and in an imposed stres s range. Similar results were obtained for both load conditions. The loss o f stiffness was used as a damage parameter and related to the rise of tempe rature. The results show Chat the damage parameter E present a nearly linea r relationship with the rise in temperature. A small deviation was probably caused by the stress release observed in the first period of fatigue life. (C) 1999 Elsevier Science Ltd. All rights reserved.