Influence of coupling agents on the adhesion force of dissimilar overmolded polymers: a digital image correlation analysis

The increase in the technical and functional requirements of plastic items has led the development of multimaterials. To achieve a good performance in the adhesion of dissimilar materials, in this case, polypropylene and coconut fiber composites, it is fundamental to understand the phenomena related to the specific interface. This work aims to evaluate the adhesion force of different multi-materials, namely between overmolded polymer-coconut composites using the digital image correlation (DIC) technique. First, coconut fiber composites were prepared using three different coupling agents, then they were overmolded with polypropylene. The results show that coupling agents have a positive influence increasing the mechanical properties of such multi-materials under tensile stress. The Lagrange vectors obtained by DIC analysis identified higher stress concentration at the joint edges, where the occurrence of surface cracks led the samples to fail in the region close to the overlap.