Material damage and buckling instability: towards a unifying general theory

ended

General structural stability theories have been hitherto restricted to elastic systems. This constitutes a significant weakness in current structural stability analysis techniques particularly owing to the increasing use of composite structures in lightweight construction. The DamBuckler project aims for this to be resolved by developing a novel generalized theory that unifies the concepts of structural stability and material damage. Hence, a novel variational principle will be developed that is capable of determining the deformation path, its stability and the damage growth behaviour of mechanical systems. The variational principle will be based on an energy functional, depending on the configuration only, which will be derived by analysing the behaviour of the energies related to elastic and inelastic deformation with respect to variations of the damage state. With the aid of the novel general structural stability theory, the effect of material damage and its propagation will be considered and analysed in the stability analysis of structures. The theory will be applied to an application example which is particularly relevant for aircraft structures: the modelling of the compressive behaviour of composite panels with barely visible impact damage. Hitherto, detailed mechanical insight into the structural stability behaviour of these structures is restricted since analytical models are confined to non-growing damage. Moreover, comprehensive finite element models, although consider damage growth, are related to certain structural configurations and damage locations. The novel general theory will enable the formulation of semi-analytical modelling approaches that will provide insight into the influence on the structural stability from varying material parameters, laminate layup, layer thickness, delamination depth and geometry, alongside the effect of multiple and distinct damage parameters such that they can be understood comprehensively and predicted with accuracy.