Analysis of thick walled composite pipes with metal liner subjected to simultaneous matrix cracking and plastic flow

Filament wound thick walled composite pipes designed for withstanding high-pressures and axial loads are designed using angle ply layers for obtaining sufficient strength and a metallic liner for obtaining a barrier against diffusion or leakage of gas and/or liquid media. The analysis presented goes beyond the formation of first ply failure and at the same time allows for plastic flow in the liner. The progressive matrix cracking is modelled using a postulated shape function of the displacement field and crack surface geometry. The effective elastic parameters, the stress and strain fields in the cracked composite layers were obtained from an approximate closed form analytical solution, deduced by variational principles. Various failure criteria can be used in order to simulate the progressive evolution of matrix cracks. The plastic flow of the liner was modelled using the method of successive elastic solutions. The analysis of matrix cracking and the plastic flow are based on incremental loading and the two failure mechanisms were modelled in a coupled and simultaneous scheme.