Rubber‐toughening of glass fiber‐epoxy filament wound composites

Abstract

An attempt was made to improve the properties of filament wound glass fiber‐epoxy composites by addition of carboxyl‐terminated‐butadiene‐acrylonitrile (CTBN)‐rubber to the matrix. The interlaminar G_Ic of unidirectional glass fiber‐epoxy increased significantly with CTBN addition whereas the flexural strength decreased. The weepage stress in hoop loading of ±50 degree angle‐ply pipes was higher for unmodified as compared with 10 phr CTBN‐modified epoxy matrix pipes. However, the strain at weepage and the stress and strain at nonlinearity were higher for the pipes based on toughened epoxy. The reason for the lower weepage stress is that, although the toughened matrix pipes show higher resistance to cracking, their stiffness is lower. The addition of small amounts of CTBN‐rubber (about 5 percent by weight is suggested) to the present epoxy matrix for filament winding can be done with only a minor increase in viscosity. This is a way of toughness enhancement for applications where the matrix stiffness reduction and increased moisture absorption are of minor importance.