A high power diode laser (HPDL)-based technique for the bonding of composite patches to aluminium alloys on various military aircraft

A rapid, effective and repeatable technique for repairing the damaged skins of various military aircraft, both fixed and rotary winged, using a high power diode laser (HPDL) is described herein. The HPDL was traversed across the surface of an APC-2 repair patch, thereby melting a thermoplastic adhesive placed in between the repair patch and an Alclad substrate, consequently bonding the repair patch to the Alclad substrate. When subjected to single lap shear tests, the shear strength of the HPDL bond was 47.8 ± 4.7 MPa, compared to 32.4 ± 3.7 MPa for the induction welded samples. When subjected to the Boeing wedge test, the HPDL samples had a 1 h crack growth rate that was rated as very good (1.9 ± 0.5 mm/h); for the induction welded samples the 1 h crack growth rate that was rated as good (2.7 ± 1.2 mm/h). Of great significance was processing time achieved with the HPDL, which was reduced from 11.75 mins when employing induction welding to 2.75 mins with the HPDL. Moreover, the HPDL has been shown in this work to be a tool for bonding that is superior to its contemporary counterparts. It is, therefore, distinctly possible that even stronger bonds could be achieved with the HPDL if different adhesives were used.