Chemical vapour infiltration and mechanical properties of carbon open-cell foams

Abstract

In order to improve their mechanical properties, carbon open-cell foams of two different pore sizes were infiltrated with pyrocarbon by chemical vapour deposition at reduced pressure and using pure propane as precursor. The optimal conditions in terms of deposition rate and uniformity in coating thickness, structure and anisotropy were first investigated. Foam specimens were infiltrated at various stages, with two pyrocarbons of distinct microtextures and their morphology, relative density and geometrical features were evaluated.Compressive crushing tests were conducted to determine the influence of the pore size, the pyrocarbon type and the relative density on the mechanical properties of the pyrocarbon-infiltrated foams. They retain their non-brittle and dissipating behaviour up to relative densities of 0.15. The stiffness, crushing strength and dissipated energy increase significantly with the relative density. The crushing behaviour of the pyrocarbon-foam specimens can be essentially explained using simple structural models and failure mechanisms, according to the Gibson & Ashby’s approach for brittle cellular solids.