The fracture toughness of composite laminates with a negative Poisson's ratio

Two sets of carbon fibre laminate configurations have been designed manufactured and examined. The first consisted of one in plane auxetic (i.e. having a negative Poisson's ratio) and one with matched elastic moduli, but a positive in-plane Poisson's ratio. The second consisted of three laminate again with matched elastic moduli but with negative, near zero and positive thru-thickness Poisson's ratio. Fracture toughness is predicted to be enhanced if a negative thru-thickness Poisson's ratio is present. This study also shows that more energy is required to propagate a crack in the auxetic laminate and that is less notch sensitive than its conventional counterpart for the negative in-plane Poisson's ratio. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim