Ultrasonic and Interlaminar Properties of Highly Porous Composites

Abstract

The effect of increasing void content (up to 30%) on the ultrasound attenuation coefficient, interlaminar shear strength and Mode I interlaminar fracture toughness properties of a glass fibre reinforced polymer (GFRP) composite were investigated. Also studied was the effect of increasing the thickness (up to 150 mm) of highly porous GFRP composites on ultrasound attenuation. A pulse-echo ultrasonics technique was used to measure the amount of attenuation through the GFRP, and this increased linearly with thickness up to 150 mm. Attenuation also increased rapidly with void content, and these measurements were used to further test the accuracy of models proposed by Martin and by Hale and Ashton for calculating the attenuation coefficient of porous composites. Poor agreement was found between the measured and calculated attenuation coefficients, and the causes for the discrepancies are discussed. As expected, the interlaminar shear strength and interlaminar fracture toughness decreased rapidly with increasing void content.