Performance of various designs of hybrid loop-loaded CFRP-titanium straps

Loop-loaded straps are capable of transmitting high tensile loads using lightweight materials like CFRP. Additionally, these loops have the benefit to implement metallic components to reduce wear between the CFRP and the connecting part. This paper investigates loop-loaded CFRP straps which integrate titanium parts into a Resin Transfer Molding process. On the textile side, preforms are manufactured by winding and by Tailored Fiber Placement. On the metal side, parts had been manufactured by Laser Additive Melting. Two metallic parts made of Ti-6Al-4V have been manufactured. The first metallic part is a hull which is placed at the one end of the CFRP strap to connect the strap to the testing machine. On the other end of the strap a titanium insert element was integrated to simulate a flange connection. Furthermore, different designs for this insert have been chosen, varying in radius and the quantity of the loops. The influence on the tensile strength depending on the design of the inserts has been tested using a tensile testing machine. The strap specimens with different cores had been manufactured and examined using a tensile test. From these test results an insight into the influences of the flange design on the mechanical tensile properties as well as failure mechanisms of the hybrid strap were determined evaluated. Hereby, it could be shown that cascaded cores provide and increased tensile strength of 5 % compared to a standard loop strap. Furthermore, different core radii have an influence regarding the tensile strength of nearly 20 % of hybrid loop-loaded straps. Finally, a crossed loop was tested with only 25 % fiber rovings like the other specimens but with a 50 % higher UTS compared to the highest UTS of a cascaded specimen