Enhanced fatigue performances of hybrid nanoreinforced filament wound carbon/epoxy composite pipes

In filament wound composite pipes matrix cracking, as an initial damage mechanism during fatigue loading, can initiate a damage sequence that can result in catastrophic failure of the pipes. Matrix modification using nanostructured fillers is an emerging approach to develop new fatigue-resistant composite materials. The aim of this study to investigate the fatigue performance experimentally, and observe macroscopic and microscopic damage mechanisms of carbon fiber/epoxy filament wound composite pipes toughened by carbon nanotubes ( CNTs) and boron nitride nanoplates (BNNPs). The effectiveness of nanofillers with different morphologies on fatigue damage development and their micro/nano reinforcing mechanisms were discussed. The fatigue tests with positive cycling pressure loading were performed at three different load levels as 50%, 60%, and 70% of the static burst strength of each samples. S-N curves were obtained according to fatigue test and lifetime of the fabricated hybrid composite pipes were evaluated. The addition of nanoscale reinforcements increase fatigue performance of the composite pipes for all cases. To analyze damage initiation and final damage, microscopic analyses of the fracture surfaces were utilized. The fractographic investigations revealed that the morphologies of nanofillers play a key role on improving mechanical performance by generating different nano- and micro-scale toughening mechanisms. (C) 2016 Elsevier Ltd. All rights reserved.