The joint strength of hybrid composite joints reinforced with different laminates materials

Abstract

The application of composite materials in structural applications is nowadays commonplace in diverse industrial sectors. Composites are usually joined with adhesive bonding due to the excellent performance and flexibility of this technique, which does not require modifications to the adherend and is able to easily join different materials. However, delamination of adhesively bonded joints with composite adherends is still a major concern as it leads to extremely low joint performance. Diverse studies have proposed techniques to reduce delamination in carbon fibre reinforced polymer (CFRP) single lap joints (SLJs), e.g., using adhesive fillets, using mixed adhesive technique, stitching or Z-pinning. Another subset of techniques attempts to avoid delamination via reinforcement of the adherend, usually by replacing layers of CFRP with polymer or metal (fibre metal laminates) in the surface of the adherend. This paper studies the effect of additional polymer and metal layer thickness inserted in the adherends on failure load and failure mode of bonded joints with composite adherends. Multiple configurations are analysed numerically for quasi-static and intermediate rate conditions using elastic and cohesive zone modelling. A noticeable increase in failure load under an intermediate loading rate was observed by replacing CFRP layers with polymer or metal layers on the outer surface of the adherends. The failure mode for the CFRP SLJs with adherends reinforced with aluminium was changed from delamination to cohesive failure (for both static and intermediate rate loading) and a higher degree of cohesive failure was observed in configurations reinforced with polymer.

Keywords

• CFRP
• Adhesive bonding
• Reinforcements
• Composite materials
• Delamination