An experimental and modelling evaluation of the deformation and fracture of quasi-brittle reticulated vitreous carbon foam

Abstract

In quasibrittle materials the addition of specific microstructural features such as porosity can lead to departure from linear elastic behaviour prior to maximum force, followed by graceful failure. A simple but extreme example is reticulated vitreous carbon foam, with its opencell structure of brittle ligaments connected in a threedimensional array. Tensile testing has been made on foams with various pore and ligament dimensions to provide a measure of forcedisplacement, combined with acoustic monitoring, and evaluation of the associated elastic moduli and fracture strengths. These tests provide insights into the mechanisms of quasibrittle failure. The results are explored by comparing with predictions from a microstructurebased finite beam element model. Inputs to the model are the elastic modulus and fracture strength of the individual ligaments of the foam measured at the micro lengthscale. Results are discussed with respect to the energy of fracture, the distribution and progression of fracture for individual ligaments.