Colloquium: João Tomás Ferreira Diniz (ASM)

This thesis investigates the use of Tow-Based Discontinuous Composite (TBDC) interleaves to enhance the mode I fracture toughness of adhesively bonded joints with Carbon Fiber Reinforced Polymer (CFRP) substrates. Two research questions are addressed: the impact of TBDC interleaves on CFRP laminates and their effect in bonded joints. Double-Cantilever Beam (DCB) tests were conducted on TBDC-toughened laminates, with fracture toughness improvements up to 130% compared to non-toughened configurations, due to mechanisms such as crack branching, deflection, and fiber bridging. Adhesive joints were tested using low-toughness Araldite 2015-1 and high-toughness AF 163-2U adhesives. Joints with low-toughness adhesive exhibited more than a 100% increase in crack length from peak fracture toughness to the final value compared to non-toughened joints. Joints with high-toughness adhesive demonstrated toughness values 150% to 750% greater than those observed in non-toughened configurations at comparable crack lengths. These findings highlight the potential of TBDC interleaves to enhance joint toughness and improve the safety of composite bonded structures.

Supervisor: Dr. Sofia Teixeira de Freitas