NUMERICAL AND EXPERIMENTAL INVESTIGATION OF CFRP TO PERFORATED STEEL JOINTS

The elastic properties mismatch between CFRP and steel makes joining them difficult. One way to reduce this mismatch is to gradually decrease the average stiffness of the steel part of the joint by perforating it. The present study investigates flat co-infused perforated steel to CFRP joint configurations that offer a transitional zone of stiffness in the joint site. Further, the possible advantage of mechanical interlocking is investigated. The steel parts are perforated with circular holes. The hole diameters are smaller near the edge of the composite, and increase with increasing depth in to the composite skins of the joint, thus creating a graded steel component. The steel part is joined to the composite by inserting it between CFRP skins. In total, five flat joint configurations are proposed for static tensile testing. These are a non-perforated joint configuration (reference) and two different patterns of perforated joint configurations. The two different perforation patterns are tested with and without PTFE material in the holes, allowing adhesive material (resin) in the holes to assess the hypothesis of mechanical interlocking. Finite element analyses are used to elucidate the experimental results. Perforated steel joints showed a 175% increase of joint strength comparing to non-perforated ones.