The Repair of Interlaminar Fracture in Thermoplastic-matrix Composites
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Tayyab KHAN , Rehan UMER (UNITED ARAB EMIRATES), Wesley CANTWELL (UNITED ARAB EMIRATES)Abstract :
In this study, pre-cracked carbon fiber reinforced composite laminates, based on an infusible thermoplastic resin (Elium®), were manufactured via the vacuum-assisted resin transfer molding process. These pre-cracks were subsequently repaired using a hot press by heating the laminates above the glass transition temperature of the cured liquid thermoplastic resin. The Mode I interlaminar fracture toughness (GIc) was investigated by conducting a series of double cantilever beam (DCB) tests and the precise contribution of each processing parameter towards the measured fracture toughness was determined using an analysis of variance (ANOVA) approach. The bonding mechanisms were investigated through microscopic analyses and X-ray Computed Tomography (XCT) and the mechanical performance of the repaired composites was also investigated through four-point bending tests.
The results revealed that the joining temperature was the most dominant parameter, with an 82% contribution, followed by the contact time which had a 12% influence. The specimens bonded at higher temperatures for longer times exhibited the highest fracture toughness characteristics, these being in excess of 0.74 N/mm, values that compared favorably with those measured on fully-infused reference samples (1.16 N/mm). The 3D models generated from XCT images showed an increase in solid volume fraction from 48% to 70% at the optimum repair parameters. The residual flexural strength of the damaged samples healed at the optimum parameters was recorded to be 96% of the reference condition. The SEM images confirmed that delamination from the previously healed crack interfaces was the most dominant failure mode in the repaired samples, in contrast to fiber fracture and brittle failure in the undamaged reference composite samples. The results show that the damaged composite laminates can be effectively healed and repaired to as good as undamaged laminates using the interdiffusion mechanism.
The results revealed that the joining temperature was the most dominant parameter, with an 82% contribution, followed by the contact time which had a 12% influence. The specimens bonded at higher temperatures for longer times exhibited the highest fracture toughness characteristics, these being in excess of 0.74 N/mm, values that compared favorably with those measured on fully-infused reference samples (1.16 N/mm). The 3D models generated from XCT images showed an increase in solid volume fraction from 48% to 70% at the optimum repair parameters. The residual flexural strength of the damaged samples healed at the optimum parameters was recorded to be 96% of the reference condition. The SEM images confirmed that delamination from the previously healed crack interfaces was the most dominant failure mode in the repaired samples, in contrast to fiber fracture and brittle failure in the undamaged reference composite samples. The results show that the damaged composite laminates can be effectively healed and repaired to as good as undamaged laminates using the interdiffusion mechanism.