Closed-form non-linear sectional analysis in the presence of delamination

A non-linear sectional analysis is presented for a composite strip with small pretwist in the presence of delamination. Variational Asymptotic Method (VAM)is used as a tool for dimensional reduction of laminated shell theory to a non-linear one-dimensional (1D)theory. Study is performed to investigate the influence of delamination on trapeze effect, which is important in rotor blades. As the developed procedure gives the nonlinear stiffness of the strip at any given cross-section,degradation in the non-linear stiffness due to the presence of delamination can be used as data to detect damage. Hence the developed model has a potential application in structural health monitoring of rotorcraf flexbeams.