The effect of fatigue damage on toughening of short-fiber-reinforced polymer composites

Fatigue fracture of fiber-reinforced polymer composites (FRP) occurs when m icrocracks are induced by debonding, pull-out and delamination at the inter face between the matrix and fiber. This microcrack area increases with incr ease in fatigue cycles and a damage region is formed. In our previous paper , fatigue life of a short fiber-reinforced polymer composite consisting of glass fibers and polycarbonate matrix was found to be related not to the ma in crack growth behavior but to the progression behavior of the damage regi on. In this paper, using our proposed real time observational system, we pe rformed detailed observations on the behavior of fatigue damage and clarifi ed the mechanism of damage progression. Furthermore, mechanical considerati ons were performed by finite-element elastic-plastic stress analysis. The r esults mentioned above indicate that control of short fiber alignment makes it possible to release the stress concentration caused in the matrix, and disperse fatigue damage. This results in an enormous improvement in fractur e toughness. (C) 1999 Kluwer Academic Publishers.