A method of manufacturing a foam showing a gradient poisson's ratio behaviour

摘要

There is disclosed a method of manufacturing a foam having a Poisson's ratio which varies across at least a region of the foam in a gradient distribution from a negative value to a positive value. The method includes the steps of: a) providing an open-cell foam (1); b) applying a compressive force (F) to a localised region (7) of the foam to collapse the foam (1) in said localised region (7), whilst leaving other regions (8) of the foam un-collapsed; c) heating the foam (1) to a predetermined temperature whilst continuing to apply said compressive force (F) to said localised region (7) of the foam (1); and d) subsequently cooling the foam (1) whilst continuing to apply said compressive force (F) to said localised region (7) of the foam. Also disclosed is a foam (1) according having a first region (7) which exhibits a negative Poisson's ratio, a second region (8) spaced from the first region and which exhibits a positive Poisson's ratio, and an intermediate region (10) located between said first and second regions (7, 8) and across which the Poisson's ratio of the foam (1) varies in a gradient distribution from a negative value to a positive value.