Development of a semi-empirical method for obtaining the dynamic Young's modulus in random continuous reinforced glass/epoxy composites

Abstract

Due to the inherent inertial effects associated with high speed testing, it may be beneficial if material properties at high strain rates could be obtained from the use of micro-mechanics. However, it has been demonstrated that using the rule of mixtures to predict material properties at high strain rates results in errors since the rate sensitivity of the Young's modulus and tensile strength cannot be explained solely in terms of the rate dependence of the resin modulus and strength (respectively) measure in isolation. A number of equations for predicting the in-plane material properties of random continuous reinforced polymer composites have been suggested in the available literature using empirically evaluated correction factors. The use of such factors in the determination of dynamic properties have, however, led to significant errors. It is therefore imperative that a method of obtaining high speed material properties of composite laminates must be sought since micro-mechanics equations have not been found suitable. This was set as the primary aim of this research work in obtaining accurate material data. In addition, the understanding of the mechanisms governing failure under high speed loadings remain largely unknown. This prompted the need to characterize the effect of loading rate on failure modes. Tensile tests were conducted on random continuous glass/epoxy composites at increasing rates of strain. The effect of loading rate on failure mechanisms was investigated by viewing fractured surfaces of the tensile specimens using a scanning electron microscope (SEM). This work postulated a semi-empirical relationship for the tensile modulus using micro-mechanics and data from tests conducted. The validity of this relationship however, needs to be investigated further in future work.

Publication Title

Journal of Reinforced Plastics and Composites

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