Shear behaviour of polyurethane foam

Abstract

Polymeric based foams are widely used as insulation or structural core materials. Typically, plastic foams such as polyurethane (PUR) are commercially available in a variety of densities and, consequently, with distinct mechanical properties to fulfil a wide range of uses and applications. Usually, in sandwich construction, PUR foams are used as core material enclosed by two external faces of higher stiffness and strength. Since the lightweight PUR foams are relatively inexpensive, they are prone to be used as core material in sandwich construction, but may limit the ultimate strength of the sandwich panels due to core shear failure. Thus, a detailed characterization of PUR mechanical properties, namely shear modulus and shear strength, is required to efficiently use these materials in structural applications. Thereby, the present study deals with the experimental characterisation of the shear behaviour of a specific PUR closed-cell foam, with density of 70 kg/m3, in particular, considering the implications of size effect on the obtained results and on the estimation of the material properties. The experimental procedure was based on the standards ISO 1922 and ASTM C273, as well as, other existing publications, considering that this PUR is intended to be used as structural core material in sandwich panels for flooring purposes. Instrumentation included a load cell, LVDTs and digital image correlation. The present work details the experimental program and analyses the main results obtained.