A novel 2-D random void model and its application in ultrasonically determined void content for composite materials

A two-dimensional (2-D) Random Void Model (RVM) is innovatively developed to describe random voids and to quantitatively correlate ultrasonic attenuation coefficient with void content of composite materials. The spatial autocorrelation function and statistical parameters are used to describe the large-scale heterogeneity from the composite matrix and the small-scale heterogeneities of elastic fluctuations from random voids. The RVMs of Carbon Fiber Reinforced Polymer (CFRP) composite specimens over a void content range of 0.03-4.62% are presented. Outstanding improvements of geometric simulations of voids morphology and quantitative correlation of porosity and ultrasonic attenuation coefficient at 5 MHz are observed. It is concluded that this method is suitable to identify random voids and to predict void content of composite materials nondestructively.