Experimental and numerical investigation of the strain rate-dependent compression behaviour of a carbon-epoxy structure

Abstract

The usage of fibre-reinforced composites in automotive body structures is still a rarity. The main goal in body structure development is to design lightweight structures as cost-efficient as possible. This research contributes to the approach of maximal material usage by considering the strength increase of a carbon-epoxy laminate with increasing strain rate. The objective was to substantiate the well-known material characteristic's strain rate dependency from a coupon level to realistic body structure component – experimentally and numerically. Hence, a special compression fixture was developed to obtain all necessary characteristic values of the investigated T700S DT120 prepreg system. The rectangular coupon specimens were loaded with quasi-static to intermediate strain rates (2×10^-4 to 70s^-1). A second compression fixture was developed to axial load omega cross-sectional specimens with strain rates from 2×10^-4 to 5s^-1. The experimental tests showed a significant increase of +23% and +21% in compression strength for rectangular coupon specimens and omega cross-sectional components, respectively. Furthermore, the numerical simulation showed the same increase in strength of +21% for omega cross-sectional components. This work has proven the necessity of considering the strain rate dependency of a composite material to accurately predict the maximum load capacity of a structure during a dynamic load event like a crash.