TESTING AND MODELING OF FAILURE BEHAVIOUR IN FIBER METAL LAMINATES

摘要

Fiber Metal Laminates (FML) are hybrid materials consisting of alternating layers of thin metal sheets and composite layers. GLARE is the best known example of these laminates and is applied in the Airbus A380. The main incentive for the development of these hybrids is their excellent Damage Tolerant behavior when compared to metal alloys. When compared to composite materials, FML offer some plasticity and can be manufactured applying simple (metal) manufacturing processes. The laminates, due to their composition, fail in modes, different from the ones for monolithic metals and full composites. Metals fail in a more or less ductile manner, composites fail by failure of the fibers and/or (subsequent) fracture of the matrix and fiber-matrix interfaces. The different constituents involved in FML, may each fail in their own failure mode: fibers in breaking, the adhesive in shear or in peel, and the metal in ductile fracture or local buckling. Assembled in a laminate also coherence failures may occur, like delamination, which occur at the interfaces between the metal and the composite layers. This delamination is induced by tensile, compressive or bending stresses, and results from high tensile and shear stresses at the interfaces. This paper discusses some experimental and numerical results of an ongoing research focused on the failure behavior of FML, and of GLARE in particular. This research is performed in a Specific Targeted Research Project under the 6th Framework of the European Commission, called DIALFAST, in a Work package about micro-mechanical modeling of FML. The work in this WP was performed by Airbus, TU Delft and EADS CRC; ALE was subcontracted by Airbus. The main objective for this work package is to develop FE-models that can predict adequately the failure of typical details in FML structures like joints, splices, etc. The models are developed to describe the failure behavior observed during the experiments and are validated with the measurements from these tests. The FE-models, as described in the paper, are used to develop design tools for the design of FML structures and to predict and describe the failure of structures and structural details in GLARE. The macro-mechanical testing and modeling is part of another Work package within the DIALFAST program. Two examples of failure, investigated during the research, are described in this paper: delamination of laminates and the failure of riveted joints.