Failure of composite pipes under local loading with A hemispherically-tipped indenter

Abstract

Summary A number of tests have been carried out in which GRP pipes were loaded quasi-statically and dynamically with a hemispherically-tipped punch. The main energy absorption mechanisms were noted and compared with those that are present in monolithic steeel tubes under similar loading conditions. The effect of projectile impact on the structural integrity of GRP pipes was investigated by internally pressurising impact damaged pipes to failure and noting the drop in burst or leakage pressure resulting from the impact. Medium term (24 hour) pressure tests were also carried out to ascertain the ability of the pipes to remain leak proof after being impact damaged. It is shown that empty GRP pipes are significantly more efficient (in terms of energy absorbed per areal density) at withstanding projectile impact than monolithic steel tubes. However, the energy absorbing capability of GRP pipes is strongly dependent on the filling medium with the minimum energy required for perforation of the pipe wall being much less for oil-filled pipes than for air-filled pipes. It is also shown that, at very low impact energy levels, the GRP pipes suffer cracking of the resin matrix which leads to leakage through the pipe when the pipes are subsequently filled with oil. This implies that although the GRP pipes can be very efficient at withstanding projectile penetration, their damage tolerance is very low. Preliminary tests indicate that fitting an internal liner to the pipes may substantially enhance their damage tolerance.