Fracture properties of high performance carbon foam sandwich structures

This paper investigates the fracture properties of high performance sandwich structures based on tough carbon fiber reinforced polyetheretherketone (PEEK) skins bonded to a carbon foam core. Single cantilever beam tests on pre-cracked samples indicated that an excellent level of adhesion can be achieved between the skin and core materials. In all specimens, the crack propagated within the carbon foam providing an additional in situ evaluation of the fracture properties of the core material. Single edge notched bend (SENB) testing was performed and revealed that both test procedures yielded similar values of fracture toughness. Three point bend (3 PB) testing on simple supported beams highlighted the excellent load bearing capabilities offered by these lightweight multifunctional structures. Optical examinations revealed that failure modes such as localized indentation; collapse and densification of the carbon foam core and cohesive bi-material crack propagation contributed to the excellent load bearing characteristics offered by these systems.