Development and optimization of an innovative joining technique for composite structures using the Finite Element method

This paper presents the numerical implementation and optimization of a novel joining technique which has a proven feasibility for composite structures, the Redundant High Efficiency Assembly (RHEA). Therefore, specially cut titanium foils were bent and inserted into carbon fiber reinforced plastic (CFRP) structures before the curing process was started. Thereby, a bonding connection between metal and CFRP is formed by the resin of the preimpregnated composite material. As shear loading is a representative load case for this joint, single lap shear was considered within this research work. In order to analyze the mechanical behaviour, a mesomechanical model of this joining technique was built up in the commercial Finite Element software ABAQUS/Standard 6.11-2. The main aspects of the numerical modeling included the implementation of Puck's failure criterion for unidirectional composite materials as well as the simulation of the bonding behavior of the metal-CFRP interface. The validation of the numerical results consisted of experimental tests of the interface properties as well as the single lap shear test of the reference geometry. The knowledge about the mechanical behavior allowed an optimization of the whole arrangement and design of the titanium elements according to shear loading, which resulted in an increased applicable load and strain of the bond.