STRESSES AND STRAINS IN HEMISPHERICAL GRP PRESSURE-VESSELS WITH RADIAL CYLINDRICAL BRANCH CONNECTIONS

Experimental strain distributions are presented for two 1 m diameter chopped strand mat glass-fibre-reinforced polyester hemispherical pressure vessels with 200 mm diameter radial branch connections. One vessel had local reinforcement around the branch. The results are compared with theoretical predictions from computer programs based on thin-shell theory (BOSOR4) and axisymmetric solid finite element analysis (PAFEC, ASAS). The finite element approach is shown to give good agreement with experimental results when detailed information of the shape of the branch hemisphere junction is provided. In-plane and through-thickness stresses and strains are examined in detail for internal pressure and a radially outward load applied to the end of the branch. Fine finite element meshes are necessary for accurate prediction of through-thickness stresses at the junction. Orthotropic material properties are considered. Delamination occurred at the junction due to through-thickness tensile stresses, but for internal pressure loading the final fracture was due to in-plane stresses.