Dynamic properties of high structural integrity auxetic open cell foam

Abstract

This paper illustrates various dynamic characteristics of open cell compliant polyurethanefoam with auxetic (negative Poisson’s ratio) behaviour. The foam is obtained fromoff-the-shelf open cell polyurethane grey foam with a manufacturing process based onmechanical deformation on a mould in a temperature-controlled oven. The Poisson’s ratiois measured with an image processing technique based on edge detection with waveletmethods. Foam samples have been tested in a viscoelastic analyser tensile test machine todetermine the Young’s modulus and loss factor for small dynamic strains. The samesamples have also been tested in an acoustic impedance tube to measure acousticabsorption and specific acoustic resistance and reactance with a transmissibilitytechnique. Another set of tests has been set up on a cam plastometer machine forconstant strain rate dynamic crushing analysis. All the tests have been carried outon auxetic and normal foam samples to provide a comparison between the twotypes of cellular solids. The results from the experimental tests are discussedand interpreted using microstructure models for cellular materials existing in theliterature. The negative Poisson’s ratio foam presented in this paper shows an overallsuperiority regarding damping and acoustic properties compared to the originalconventional foam. Its dynamic crushing performance is also significantly superior to thenormal foam, suggesting a possible use in structural integrity compliant elements.