Abstract: A steel liner (a pipe or vessel) is wrapped with a stack of sheets of glass fiber-reinforced epoxy matrix composite arranged in angle-ply pattern. The stack is cured on the liner to bond the sheets together and to the liner. The wrapped liner is then internally pressurized to cause the liner to yield while the composite remains elastic. When de-pressurized, the liner has compressive residual stress and the composite has tensile residual stress. When the resulting hybrid structure is subsequently again pressurized, it is found that the elastic regime of the liner has been extended.