Filler-enhanced crashworthiness of high performance composites

Energy absorption is an increasingly important function of structural materials as it is now an essential requirement in the design of almost any means of transportation. The capability of absorbing energy in the unfortunate event of a crash is often referred to as the crashworthiness of a structure. In the pinnacle of motorsport; Formula One, this capability is stretched far beyond industrial performance. Traditionally, metals have been the most commonly used materials for crashworthy structural applications due to their plastic deformation characteristics that enable them to absorb impact energy in a controlled manner. Unlike metals, polymer composites materials do not typically exhibit extensive plastic deformation due to relatively low failure strains, though still yield superior performance. The superior energy absorbency of composites is achieved due to extensive localized microfracture processes of the composite occurring in a crush zone which propagates through the whole structure, a process which is denoted as progressive crushing. 

In order to push the boundaries of performance even further, the intrinsic deformation behaviour of epoxies is studied by measuring the intrinsic true stress-strain response. Upon analysing the response with the help of constitutive models, the flaws of epoxies surface and can be mitigated by heterogenization of the microstructure, i.e. adding filler particulates. These microstructures are subsequently analysed and optimized by implementation of the state-of-the-art EGP constitutive model for multiple relaxation times, all within a continuum model based on Representative Volume Elements.