Gecko Inspired Adhesive Patterned Single-Lap Joints

Biology inspires innovation throughout the fields of science and engineering. Inspiration can be found from a dolphin's aerodynamic shape creating low resistance while swimming to a gecko's unique patterned feet, enabling adhesion to almost all surfaces. In industry, lightweight and high strength structures are desired due to their high specific strength performance. To accomplish the desired requirements, nontraditional methods of joining, such as adhesive joints, are often demanded. Adhesive joints play a vital role in today's aerospace applications, as they allow the joining of dissimilar materials to achieve the desired high energy-saving performance. The properties of the adhesive significantly affect the strength of the joint, where hightoughness adhesives can be more beneficial for longer overlap lengths, but less beneficial at high-temperatures; while low-toughness adhesives provide high strength and stiffness over short overlap lengths, but exhibit sudden brittle fracture at lowtemperatures. Hybrid adhesives can combine both high strength and high ductility over a wide range of temperatures and be used to control crack propagation. This work numerically and experimentally studies the effect of gecko-inspired surface patterns on the damage growth and failure mechanisms in a Titanium (Ti) and Carbon Fiber Reinforced Polymer (CFRP) adhesive single-lap joint (SLJ). Finite Element Analysis is performed utilizing Abaqus® paired with Cohesive Zone Modeling to observe the damage growth of the hybrid adhesive based on the material directionality. By implementing directionality to the adhesive properties, the rate at which adhesive failure occurs can be controlled, and the failure mechanisms of the SLJ can be observed. This study applies the concept of biomimicry to evaluate the effect of gecko-inspired hybrid adhesive patterning on the failure mechanisms and strength of SLJs, with the aim to path novel designs for composite adhesive joints.