On a Damage Growth Mechanism in a Hoop Layer of Filament Wound Pressure Vessels

Abstract

A damage growth mechanism in a hoop layer of a cylindrical portion of a composite pressure vessel was analytically studied. The cylindrical portion was produced by winding finite width prepreg tape, and made of two layers which consist of a circumferentially wound hoop layer and an almost axially reinforced base angle-ply layer. The fibers of the hoop layer were slightly inclined from the circumferential direction for the tape to be wound without gap and overlapping each other. So, the hoop layer forms a very low angle-ply laminate. High tensile strains generated in both axial and hoop directions due to the high internal pressure may produce matrix cracks in the full depth of the hoop layer, because the surface unevenness of the damage due to the different fiber angle is very small as the crack just initiates. However, the damage growth is not simple in this case because the unevenness increases with the crack growth without fiber breakages. The growth of uneven damage was examined through a fracture mechanical study based on the channeling crack assumption, but found to be difficult. It is concluded that the crack growth must accompany some fiber breakages or fiber peel-off from the cracked surface.