Compression Strength and Taguchi L9 Design of Auxetic Polyurethane Foams for Rehabilitation Applications

Abstract

Auxetic foams are known to exhibit unique mechanical properties such as indentation resistance, higher pressure distribution and shear stiffness. These foams can be tailor-made, by varying the parameters used in the fabrication process, to suite different applications. In this work, Conventional or Normal PU (NPU) foams are converted to auxetic PU (APU) foams using a thermo-mechanical process. Heating temperature, compression factor and heating time are the process parameters which effects the auxeticity of the resulting foam. Taguchi L9 design methodology is used in this work to arrive at the ideal fabrication process parameters for cushioning applications. NPU foams were converted to APU foams using 9 sets of process parameters. Poisson’s ratio values of these APU foams were found using digital image correlation technique and MATLAB software. Compression tests were performed for all the samples and compression strength was determined. Highest compression strength of 0.02 MPa and lowest Poisson’s ratio of -0.95 were obtained. Further studies with larger samples are required to determine the ideal foam for medical cushioning applications.