Experimental and numerical determination of adhesive strength in semi-rigid multi-layer polymeric systems

A test methodology to evaluate the adhesive strength of poly(ethylene terephthalate) (PET) multi-layer articles was developed by implementing a linearly increasing normal load scratch test (ASTM D7027-13/ISO 19252:08). The adhesive failure load between the layers and the failure modes near or at the interface were experimentally determined. The load required to induce adhesive failure and the scratch coefficient of friction were determined from the scratch test. The role of substrate deformability on adhesive failure during the scratch test was also investigated. Finite element method (FEM) modeling was carried out to investigate the corresponding stress state that causes adhesive failure to occur during scratching. FEM simulations allow for the geometric factors and material constitutive behavior to be taken into account in determining the interfacial stresses in the multi-layer system. By combining the scratch test with FEM modeling, the proposed approach can semi-quantitatively assess the delamination strength of semi-rigid multi-layer polymeric systems.