Inelastic Energy Curves: A Tool for Evaluating the Impact Response of Composite Plates

Abstract

The elegance and paramount value of composites manifests in the ability to tailor a structure for a given task such as maximizing energy absorption in a cost and weight efficient manner. A combination of factors, including recent developments in commercially available fabric architectures and resin transfer molding techniques, have led to a resurgence of interest in several classes of low-cost fiber reinforced composites for resistance to low velocity impact. Inelastic Energy Curves (IEC) are introduced as a tool to facilitate interpretation of data generated by instrumented drop weight impact towers. A general form of IEC is presented which describes distinct regions of failure. Results are presented for four representative E-glass fabric architectures in resin transfer molded composites with impact energies varying over the range to complete puncture. Since IEC's map the progressive degradation of energy transfer capability between the local impact zone and the global structure they may have applicability in interrogating generic failure processes which are prevalent in other layered composite systems. It is generally understood that matrtix properties govern the damage initiation threshold and that fiber properties control penetration resistance; IEC provide a means of identifying and quantifying what happens in between these two extremes.