AUXETIC POLYETHYLENE - THE EFFECT OF A NEGATIVE POISSON RATIO ON HARDNESS

Recent papers have described a particular form of ultra high molecular weight polyethylene (UHMWPE) which possesses a large negative Poisson 's ratio (nu) because of its complex microstructure. Classical elastic ity theory predicts that this should lead to enhancements in certain m echanical properties and this paper examines one such property-that of ball indentation resistance or hardness. The hardness of auxetic UHMW PE with a negative nu, compression moulded UHMWPE and a microporous fo rm of UHMWPE with a positive nu was measured. It was found that the pr esence of a negative nu resulted in enhancements of the hardness by up to a factor of 2 over conventional UHMWPE.