STRAIN-DEPENDENT BEHAVIOR OF MICROPOROUS POLYETHYLENE WITH A NEGATIVEPOISSON RATIO

Recent papers have discussed particular forms of expanded polytetraflu oroethylene (PTFE) and ultra-high molecular weight polyethylene (UHMWP E) that exhibit large negative Poisson's ratios due to their complex m icrostructures. These consist of an open network of nodules interconne cted by fibrils. Two geometric models have been developed to explain t he effect in PTFE; one based on nodule translation and the other on no dule rotation. Data are presented for the strain-dependent variation o f the Poisson's ratio of UHMWPE under compression and the models are a pplied. The translation model alone accurately describes the variation s in Poisson's ratio as a function of compressive strain.