Viscoelastic interlaminar shear modulus of fibre reinforced composites

An inverse parameter identification technique using a modified Iosipescu shear test (MIST) has been developed for determining the viscoelastic interlaminar shear modulus of composite laminates. The main component of the technique involves minimising the difference between an experimentally measured and a numerically determined creep response at various elevated temperatures by varying the interlaminar shear modulus terms in the numerical model. Consequently, the ‘optimum’ model for the viscoelastic interlaminar shear modulus can be found at each temperature. These individual models are then combined to form a single ‘master curve’ for which a time-shift function and a Prony-series is fitted. In the present studies, Hexcel F593–18 plain weave pre-preg laminates were investigated. Experimental creep tests were conducted at various temperatures between 40 °C and 150 °C. Through the application of the inverse parameter identification technique, it was determined that the viscoelastic interlaminar shear moduli of the composite material can be effectively modelled by a nine-term Prony series and a third-order polynomial time-shift function.