Development of adhesive and cohesive failures in EVA-backsheet structures in environmental testing

The development of adhesive and cohesive failures at the EVA-backsheet interface under different damp-heat (DH) testing condition is investigated in this paper. The adhesive and cohesive failures are classified by the surface roughness of the peeled off backsheet strips. Different DH testing condition leads to different dominating failure modes. The adhesive failure is the main failure mode at lower testing temperature, which has been masked by the mixed failure mode at the higher testing temperatures due to the different temperature acceleration factor of the two processes. Development of accelerated environmental testing protocol requires the failure mode analysis to ensure the target failure mode or degradation mechanism is accelerated and not masked by any other processes.