Indentation of laminated filament-wound composite tubes

The finite element method has been used to analyse the behaviour of thin-walled, 100 mm diameter filament-wound GRP tubes supported on a flat plate and indented with a 50 mm diameter spherical indenter. The tube wall was treated as an angle-ply laminate and a half-tube model was employed with appropriate rotational symmetry conditions. The strain results were compared with those from a quarter-tube monolithic material model (homogeneous throughout and orthotropic with principal axes coincident with the axial and circumferential directions). The theoretical predictions were compared with experimental results. Local resin cracks occurred under the indenter. Two-cover (four-layer), 1 mm thick, ±55° and ±75° winding angle tubes finally failed at large indenter displacements by local shell buckling caused by the development of local axial compressive forces some distance away from the indenter. Four-cover (eight-layer), 2 mm thick, ±55° tubes delaminated under the indenter and failed by shell fracture, again some distance away from the indenter.