Assessing the application of Hi-Lok registered fasteners for the repair of open-hole and delaminated CFRP

This research investigates the potential of applying low-cost Hi-Lok registered fasteners as a temporary repair method for delamination damaged CFRP. Impact testing was performed on CFRP T800S/3900-2B coupons at three impact energy levels (5J, 10J and 20J). The strength and failure strain of delaminated, open hole and delaminated fastened (Hi-Lok registered ) specimens were then measured and compared using quasi-static testing in tension and compression. Digital Image Correlation (DIC) was used to support strain gauge measurements and analyse the stress distribution in undamaged filled-hole specimens. In compression the fastener was shown to increase the coupon strength and failure strain when compared to damaged and open-hole specimens for all energy levels. Numerical simulations using the implicit method within LS-DYNA 971 highlight the importance of hole tolerance and contact between the Hi-Lok registered fastener and coupon. The simulation results showed close agreement to theoretical stress distributions and the stress-strain response of experiments in tension and compression.