Crack-growth relationships for glass-reinforced plastics and their application to design

Abstract

Crack-growth tests under zero-tension fatigue loading were carried out on a chopped strand mat and a glass-fabric-reinforced polyester resin. A compliance calibration technique was used to measure crack growth so as to overcome difficulties with visual measurement. The Paris (1957) power relationship based on stress intensity factor range was applicable to the results, but the value of the exponent was much greater than reported values for metals and polymers. It is suggested that a crack-growth criterion could be used as the basis of a safe-life design method overcoming difficulties associated with conventional fatigue data in extrapolating to long lives and allowing for size effects and for incipient damage.