Ultrasonic and interlaminar properties of highly porous composites

The effect of increasing Void content (up to 30%) on the ultrasound attenua tion coefficient, interlaminar shear strength and Mode I interlaminar fract ure toughness properties of a glass fibre reinforced polymer (GFRP) composi te were investigated. Also studied was the effect of increasing the thickne ss (up to 150 mm) of highly porous GFRP composites on ultrasound attenuatio n. A pulse-echo ultrasonics technique was used to measure the amount of att enuation through the GFRP, and this increased linearly with thickness up to 150 mm. Attenuation also increased rapidly with void content, and these me asurements were used to further test the accuracy of models proposed by Mar tin and by Hale and Ashton for calculating the attenuation coefficient of p orous composites. Poor agreement was found between the measured and calcula ted attenuation coefficients, and the causes for the discrepancies are disc ussed. As expected, the interlaminar shear strength and interlaminar fractu re toughness decreased rapidly with increasing void content.