Collapse of Composite Rings Due to Delamination Buckling Under External Pressure

Abstract

The collapse of cylindrical shells under external pressure is known to be controlled by global elastic buckling, material failure, or a combination thereof. In the case of composites, delamination is another factor affecting the stiffness and stability of the structural component. Thin inner delaminated layers are expected to locally buckle inwards, under hoop compression, reducing the effective thickness of the ring wall. This may lead to a premature collapse of composite rings. The problem is numerically treated and parametrically studied. A Fourier series-based finite-element model is formulated for delaminated composite tubular cross sections. A special “chord length” procedure is developed to enable the convergence of the local buckling solution in quasi-static nonlinear analysis. Parametric studies are conducted to assess the influence of delamination length, depth, location, out-of-roundness imperfection, and ring layup on the pressure levels at delamination buckling and collapse.