An Experimental Study of Novel Cold Worked Penetrative Reinforcement of GFRP/ Aluminium Bonded Joints

Abstract

Stronger, lightweight materials exhibiting fail-safe failure modes are increasingly becoming a necessity amidst concerns of dwindling energy sources, rising pollution levels, and a consumer desire for constantly improving technology. The requirement for stronger and lighter materials has given rise to the implementation of fiber reinforced polymers (FRP). For FRP, metal face sheets are often added to form fiber metal laminates for improved damage tolerance. Bonding of composite materials to metals is challenging. One of the ways to improve the bonding is to use penetrative reinforcements, instead of chemical treatment. Unfortunately, the processes required to produce such modified surfaces is costly, and energy prohibitive for full-scale implementation. The use of a cold working process to form similar penetrative reinforcements provides a more environmentally friendly method. The investigation of the properties of this technology employed on a single shear lap joint is investigated in this thesis to determine ultimate strength, fatigue performance, impact fatigue, and finally failure modes under different surface configurations. Use of a novel tumbling method to test impact fatigue is developed and test results are reported here. Ultimate tensile strength is found to be comparable to non-reinforced joints, fatigue performance is found, however, to decrease in comparison to non-reinforced joints, and impact fatigue is found to be exceptional compared to non-reinforced joints. Joints with cold-work reinforcements show a substantial increase in failure energy, and damage tolerance. The modified joints show promise for use in a fail-safe design.