EFFECT OF VOID CONTENT ON THE STRENGTH OF COMPOSITE LAMINATES

An experimental program was conducted to assess the effect of void content on the static strength and fatigue life of composite laminates under flexural loading. The fabrication procedure used to produce carbon/epoxy laminates with reasonably uniform void content and constant fiber fraction is described. A fracture criterion correlating the ultrasonic attenuation to the strength of composite laminates is presented. Good correlation with experimental results of interlaminar shear and flexural strength was obtained. The fatigue test results and the proposed theory indicate that voids have a strong detrimental effect on the fatigue life of composite structures if the void content is above a critical value. The proposed theory provides the basis of an experimental program aimed at determining the maximum allowable ultrasonic attenuation of a composite laminate for a specific loading condition.