Utilization of moiré interferometry to study the strain distribution within multi-layer thermoplastic elastomers

Abstract

The use of soft elastomeric cushion form bearings as an alternative material to ultra-high molecular weight polyethylene (UHMWPE) has been proposed in the literature as providing enhanced lubrication and lower friction. However, the abrupt change in stiffness between the bearing's soft contact layer and its rigid support substrate results in high shear stresses and leads to the debonding of the soft layer from the substrate. The use of functionally modulus-graded material has been proposed as a solution to this problem. This paper investigates the use of moiré interferometry to study the strain distribution within and across the interfaces of multi-layer elastomeric samples, which were fabricated as models for functionally modulus-graded materials. While this technique has been widely used to study the strain distribution in rigid materials and composites, this paper represents the first report of its application to low-modulus polymers at temperatures where they exhibit significant viscoelastic behavior. The results presented clearly demonstrate that the moiré interferometry technique can be successfully applied in the field of low-modulus elastomeric materials. The analysis of the moiré patterns suggests that the soft elastomeric material under the contact point was subjected to a compressive εx and was pushed sideways. The analysis also showed that the maximum shear strain occurred where the deformation was constrained, which could possibly lead to a local fatigue failure in the sample.