The Influence of the Constituent Properties on the Residual Strength of Glare

Aircraft manufacturers like Boeing and Airbus are currently designing new, high capacity aircraft, e.g., A3XX. To make this aircraft cost effective for the next 30 years, a strong impulse is given to the development of new technologies like the application of new aircraft materials. One of these studies investigates the feasibility of using the Fibre Metal Laminate Glare in the damage tolerance critical upper part region of the aircraft in order to reduce weight and increase safety. The present study investigates the crack resistance of Glare in case of foreign object damage as a function of the constituent's characteristics. An experimental program has been performed on Fibre Metal Laminates built up from several combinations of aluminium alloys and fibres. Especially the fracture mechanism was studied. It was found that a larger strain hardening region and a lower yield stress of the aluminium layers had a positive influence on the residual strength due to the capability of transferring high loads away from the cracked area. Increasing the stiffness and lowering the ultimate strain of the fibres reduces the residual strength, since stiffer fibres attract more load and because the final fracture is dominated by fibre failure.