Fatigue behaviour of continuous glass fibre reinforced composites

A study has been undertaken of fatigue in glass fibre reinforced composites. Two matrix resins were tested: a standard polyester and a polyurethane-vinyl-ester, which was designed to have a higher toughness. Three different types of glass fibre fabrics were used for reinforcement: a conventional woven roving and two stitch-bonded cloths. The glass cloths were combined into various lay-ups, in order to consider the effects of matrix, cloth and lay-up on the fatigue strength. Additionally, a study was undertaken to evaluate the micromechanisms that occurred during fatigue and how damage accumulated throughout the sample lifetime. This involved measuring stiffness changes during fatigue cycling, followed by microscopic study of the samples. It was found that similar damage micromechanisms occurred in each lay-up regardless of resin and cloth type, and these included matrix cracking, delamination and fibre breakage. However, differences were observed in the extent, location and rate of damage, and these were consistent with the variations seen in the fatigue strengths.