Compound joint: A novel design principle to improve strain allowables of FRP composite stringer run-outs

A novel design principle is presented and tested, which is able to significantly improve the crack initiation loads of composite panels with stringer terminations. Taking advantage of the stable crack growth in such structures, an artificial crack is introduced which promotes synergistic load transfer of the bolts with the bond-line, drastically reducing the strain energy release rate at the run-out tip and increasing the load transfer capability of the joint.