Auxetic composite materials can be produced either from conventional components via specially designed configurations or from auxetic components. This paper reviews manufacturing methods for both these scenarios. It then looks at the possibility of property enhancements in both low velocity impact and fibre pull out due to the negative Poisson's ratio. Tests revealed that auxetic carbon fibre composites made from commercially available prepreg show evidence of increased resistance to low velocity impact and static indentation with a smaller area of damage. Also, using auxetic fibres in composite materials is shown to produce a higher resistance to fibre pullout.

Carbon fibre laminates were produced with matched throughthe-thickness modulus, but with negative (auxetic), positive and near zero through-the-thickness Poisson's ratios. These were indented with noses of diameter 2, 12.7 and 20 mm. Enhancements in indentation resistance were seen for the auxetic laminates with smaller, more localized damage areas for the two larger diameter indentors where delamination was the dominant failure mechanism. Little difference was seen in mechanical properties for the 2 mm diameter indentor where fibre breakage was the dominant failure mechanism, though smaller damage areas are still obtained in this case due to delamination growth suppression.

The low velocity impact resistance of auxetic carbon fibre laminates has been compared to that of laminates with matched through‐the‐thickness modulus, but with Poisson's ratios of near zero and positive values. Four impact loads corresponding to major events in the static indentation response were examined and damage was assessed by ultrasonic C‐scans, detailed fractography and measurement of residual properties. It was found that enhancements were seen in resistance to low velocity for the auxetic laminates, but only at low energy levels, indicating some degree of rate dependency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)