Fatigue and damage tolerance aspects of metal laminates

Abstract

In the DAILFAST program (EU KP6 program), a number of new metal and hybrid technologies have been investigated. Main objectives were to improve the properties of structural materials and concepts and to reduce the manufacturing costs. Part of this research was aimed at the improvement of the fatigue and damage tolerance properties of selected Metal Laminates and structures made of these laminates. The constituents of these Metal Laminates were state-of-art aluminum alloys, having several thicknesses, and adhesives. In the program a number of static properties have been tested on coupon level. The results of most tensile dominated tests showed that, as expected, the static properties of the Metal Laminates are equal to the properties of monolithic materials. For some other properties that are related to shear and/or compression loading some improvement is achieved. Other properties related to damage tolerance showed the potential for improvement, one is the impact resistance. Coupons tested in a drop tower test showed that most laminates perform significantly better than monolithic materials. Also the fatigue resistance of the metal laminates is higher when compared to monolithic alloys: in general, the increase of fatigue life is in the order of 10-20%. These results are based on tests with specimen with through the thickness holes. Further improvement of the fatigue and damage tolerance behavior of Metal Laminates structures is achieved by proper design and manufacture of those structures. Metal Laminates can be tailored for its purpose by selecting the right combinations of constituents and the right local thickness. This tailoring is achieved by the natural application of doublers, local reinforcements and other local features bonded onto the. To demonstrate the effects of tailoring, a number of small and medium size panels have been designed, manufactured and tested. At coupon level a number of joint types and joint configurations were tested statically and in fatigue. These tests showed that the best joining method is adhesive bonding. The panel tests showed that a weight reduction of 10 to 13% is possible when compared to riveted structures. The manufacture of these panels however, is more expensive. © Springer Science+Business Media B.V. 2009.