Post-buckling behaviour and delamination growth characteristics of delaminated composite plates

The problem of a delaminated composite plate subjected to in-plane compressive loading is investigated by employing a novel analytical framework previously developed by the authors. The framework is capable of modelling the post-buckling behaviour considering damage growth by using a set of generalized coordinates only. Therefore, in order to model the post-buckling responses of delaminated composite plates a Rayleigh–Ritz formulation is employed. Thus, the post-buckling behaviour as well as the delamination growth characteristics are determined by solving a set of non-linear algebraic equations only. For the cases investigated, the study reveals that delamination growth is associated with the global buckling response. So long as stable delamination growth is present, the post-buckling response remains also stable. However, unstable delamination growth may be caused which would occur unexpectedly yielding sudden failure of the structure. This underlines the importance of considering delamination growth when studying the structural stability behaviour of these structures

Buckling and postbuckling behavior of delaminated composite struts

The buckling and postbuckling behavior of composite struts under uniaxial compression is investigated. A geometrically nonlinear model comprising only four generalized coordinates is applied to multi-layered struts built up of transversally isotropic unidirectional layers. Laminates with a cross-ply layup are investigated. By minimizing the total potential energy of the system, equilibrium paths and critical buckling loads for varying lengths and depths of delamination are determined. Thus, the response of the system in the postbuckling range is analyzed and areas of stable and unstable behavior are determined. The outcome of the work provides detailed information about the influence of delaminations on the buckling behavior of composite struts

An analytical framework to extend the general structural stability analysis by considering certain inelastic effects-theory and application to delaminated composites

An analytical framework which incorporates damage propagation/growth into the general structural stability analysis is presented. Therefore, the conventional total potential energy approach is extended by introducing an extended total potential energy-like functional capable of describing inelastic processes in which equilibrium holds between available and the required force for producing a change in structure. The work deals with systems which are described by I generalized coordinates and K damage parameters. The damage parameters are found to be functions of I generalized coordinates and M load parameters. The underlying variational principle for inelastic solids may be solved using discrete formulations or approximate methods such as a Rayleigh–Ritz formulation. This leads to a set of non-linear algebraic equations, comprising post-critical equilibrium paths and damage propagation. In order to verify the framework, it is applied to the well-known problem in which a delaminated composite strut/plate is subjected to an in-plane compressive load