Stepped Flush Repairs for Primary Composite Structures

Optimisation study of tapered scarf and stepped-lap joints in composite repair patches

“…analysis of bondline stress without any pre-existing flaws or in-service damage), damage tolerance must also be considered for a complete assessment. A recent study by Wang et al [19] investigated the effect of step corners on the fracture behaviour of stepped-lap joints, and found that stepped-lap joints can be designed to meet design ultimate strength requirements to tolerate impact damage. As such, stepped-lap joints can in fact provide an alternative to tapered scarf joints in terms of stress distribution and damage tolerance requirements with carefully chosen joint design parameters.…”

“…However, tapered scarf repairs can be difficult to apply depending on the repair configuration. Stepped-lap joints offer an alternative that is easier to perform and less timeconsuming to produce [19]. However, the design of stepped-lap joints must be carefully investigated in order to avoid generating stress concentration at step corners.…”

Experimental and Numerical Investigations of Honeycomb Sandwich Composite Panels With Open-hole Damage and Scarf Repair Subjected to Compressive Loads

“…For the two dimensional adhesive tests, Wang [16] found that the stacking sequence, laminate thickness, and adhesive yielding had effects on the repair strength due to a variation in stiffness along the scarf. He also concluded that stepped repairs could be designed to rival the performance of scarf repairs, due to the similarity in the inherent stress concentrations at ply terminations in both repair configurations [17]. Darwish [18] obtained that the repaired panels restored 95% of the primary tensile strength value through the tensile static tests on original and repaired panels.…”

Bonded aerospace repairs under tensile loading: Wet chemical surface treatment and selected environmental conditions

“…Benefiting from, for example, low weight and high stiffness, composite materials are extensively used in new generations of aircraft (for instance, 50 wt % in the Boeing 787) . Hereby, primary flight‐critical and secondary operation affecting structures are constructed from these materials . Until March 2018, 1318 Boeing 787 and 854 Airbus A350 were ordered, whereas 670 Boeing 787/ 159 Airbus A350 were delivered .…”

“…From these numbers in combination with a variety of damage sources, for example, manufacture‐induced defects, damage by environmental conditions as well as impact damage occurring in service, during assembly or during maintenance, the necessity to develop repair strategies for composite components is obvious. Replacement poses, in many cases, not the most economic option . In this context, bonded repairs offer distinct advantages in comparison to mechanically fastened repairs, such as a beneficial stress distribution, surface smoothness, and weight reduction .…”