Investigation of compression after impact (CAI) response of filament wound grp pipes

The GRP (Glass Reinforced Polymer) composite pipes produced by filament winding technique are used in many fields such as the transmission of pressurized chemical liquids, industrial liquids, oil and natural gas transmission and construction materials. GRP composite pipes may be subjected to low speed impacts for various reasons both during installation and service. The impact on the CTP composite pipe wall may lead to some nonvisible damages such as matrix crack, fiber damage, and inter-layer separation. Composite pipes suffered strength loss due to these damages caused by impact cannot support the expected strength values during service. Pipes with three different diameters (Ø54, Ø72 and Ø96 mm) were produced to investigate the damage caused by low velocity impact and to determine the effect of these damages on the strength losses of the composite pipe. In order to investigate the influence of low velocity impact damage, the produced pipes were subjected to impacts at the velocity of 1.5, 2, 2.5 and 3 m/s according to ASTM D 7136 and preliminary damage was formed. During low velocity impact tests, Force-Time, Force-Displacement and Energy-Time graphs were obtained and dynamic behavior of the pipes were examined. In order to examine the effects of damages on the strength of post-impact pipes, Compression after impact (CAI) tests were performed on pre-damaged pipes according to ASTM D 7137 and Force-Displacement graphs were obtained. The results of impacted samples were compared with the behavior of non-impacted samples. Damages and data obtained during low velocity impact and compression after impact tests were recorded. After the experiments, macro/micro damage analyses of GRP pipes were performed by optical microscope and SEM imaging.