No abstract

In this work, we show that mechanically anisotropic short carbon fibre (sCF)reinforced epoxy foams with an isotropic cellular structure can be fabricated from liquid foam templates. Short carbon fibres were mechanically frothed in an uncured liquid epoxy resin to produce an air-in-resin liquid foam template, followed by subsequent polymerisation to produce sCF-reinforced epoxy foam with an isotropic cellular structure. Fracture toughness test showed that the incorporation of chopped carbon fibres into epoxy foams led to a significant increase in critical stress intensity factor. It was also observed that neat epoxy foams failed catastrophically whilst sCF-reinforced epoxy foams failed in a progressive manner. Compression test further showed that the in-plane compressive moduli of mechanically frothed sCF-reinforced epoxy foams were significantly higher than their out-ofplane compressive moduli, signifying an anisotropic mechanical response. This anisotropic mechanical response stemmed from the radial flow generated by the high intensity mechanical frothing process, facilitating the preferential orientation of the added chopped carbon fibres in-plane whilst the entrained air bubbles during the mechanical frothing process were in equilibrium with the surrounding uncured liquid epoxy resin, resulting in an epoxy foam with an isotropic (spherical) cellular structure.