Effects of glass fiber size composition (film-former type) on transverse cracking in cross-ply laminates

Transverse cracking is an important phenomenon in the context of fluid leak age in pipes and pressure vessels. Multiple transverse cracking in [0/90](S ) glass-fiber-reinforced vinylester and epoxy laminates with six different fiber surface treatments (size) is examined. Film-former composition is the variable since this component can be easily changed also in commercial siz e formulations. The influence of the film-former polymer on transverse crac king is significant in epoxy laminates and very strong in vinylester lamina tes. Both onset of transverse cracking and slope of crack density vs, strai n are influenced. Remarkably low crack densities were observed in some viny lester laminates. Micromechanisms of cracking are interpreted. Correlation is established between transverse cracking behavior and interfacial shear s trength measured by single fragmentation tests. The strong film-former effe ct is proposed to be due to a combination of improved interfacial adhesion and the plasticizing effect from the film-former on the interphase region. (C) 2000 Elsevier Science Ltd. All rights reserved.