A thick cellular structural adhesive: Identification of its behavior under shear loading

Abstract

This study focuses on the link between the microstructure and the mechanical behavior under shear loading of a thick cellular structural adhesive (TCSA). X-ray microtomography and image post-processing were first used to perform 3D-quantitative microstructure analysis. The cells morphometric parameters and their orientations were studied. The foaming process boundary conditions seems to create local density gradients changing the cells dimensions and shape. The cells are more spherical in the core of the material whereas being more ellipsoidal close to the upper and lower faces of the samples creating a skin layer. The effect on the strain field of this skin layer has then been highlighted. Secondly, a shear test method using an Arcan setup coupled with digital image correlation was used and allowed to observe the mechanical behavior of the material under shear loadings. Instead of the material being cellular and heterogenous, it has been found that the strain field can be considered homogeneous at macroscopic scale to extract the properties on a homogeneous equivalent material. Shear test on samples with different densities were performed. Using the relation developed by Gibson and Ashby linking the shear modulus to the density squared is a first approximation, at this scale, to predict and describe the mechanical behavior under shear loading.