Details of Static Nonlinear Analysis

As before, a linear stability analysis was performed to find the critical loads at which significant deformation will appear. The critical loads associated with delamination buckling and overall buckling were found to be 157.6N and 721.0N respectively. It will be seen as delamination buckling and growth occur the effective center of stiffness moves downwards and as a result some overall bending occurs at a fraction of the critical load associated with overall buckling predicted by linear stability analysis. This is clearly an example of interaction of delamination growth and overall buckling.

Load was introduced by prescribing end-shortening as before. The maximum end-shortening of 2mm is selected which is about 2.5 times that corresponding to delamination buckling. Small equal and opposite loads increasing from zero to 1N were applied at the bottom and top nodes respectively at the center of the column to prompt the delamination to remain open. End-shortening was applied in small increments, 1000 increments to reach a value of 2mm.