Effect of strain rate on piezoelectric characteristics of unidirectional glass fiber epoxy composites

Several researches on nondestructive damage monitoring of composite materials by piezoelectric method had been conducted recently, and concluded that the piezoelectric method can be useful for glass fiber epoxy composites. However, few studies were performed about piezoelectric properties of composites despite the importance for analyses of the electro-mechanical coupling systems. Therefore, in this study, the effect of strain rate on the piezoelectric characteristics of unidirectional glass fiber epoxy composites (UGFEC) was investigated. Under various strain rates, stress—strain curve and charge output signal from composite specimens were obtained by experiments. From experimental results, through-thickness modulus increased but electric charge output decreased linearly by increasing the strain in log scale. And piezoelectric strain constant of UGFEC was almost same while piezoelectric stress constant decreased with respect to the strain rate. From the results, it was concluded that electric charge output of UGFEC is influenced by the strain itself rather than by the strain rate.