Healing of aerospace carbon-epoxy composites using thermoplastic agents.

Pingkarawat, K 2014, Healing of aerospace carbon-epoxy composites using thermoplastic agents., Professional Doctorate, 2014, RMIT University.


Document type: Thesis
Collection: Theses

Attached Files
Name Description MIMEType Size
Pingkarawat.pdf Thesis application/pdf 7.18MB
Title Healing of aerospace carbon-epoxy composites using thermoplastic agents.
Author(s) Pingkarawat, K
Year 2014
Abstract The general aim of this PhD project is to investigate the self-healing of aerospace carbon-epoxy composites using thermoplastic agents. The project explores key parameters on the healing process, including the type, volume content and shape of the thermoplastic agent, repeatability of the healing process, and healing method (convection heating, ultrasonic welding). The PhD also investigates the influence of thermoplastic agents on the in-plane properties of carbon-epoxy composites. It was found that poly[ethylene-co-(methacrylic acid)] (EMAA) was capable of repairing delamination damage and recovering the mode I interlaminar fracture toughness and fatigue resistance. High recovery (~300%) to the mode I interlaminar fracture toughness was achieved after healing via the formation of a large-scale crack bridging zone consisting of highly ductile EMAA ligaments, which is a delamination toughening mechanism unique to thermoplastic healing agents. The carbon-epoxy composites retained high healing efficiency following multiple repair operations due to the ability of EMAA to reform the crack bridging zone. EMAA was also capable of recovering the mode I fatigue resistance (defined by Paris curves) of the composites following healing. The PhD thesis presents a comparative experimental study into the healing efficiency of EMAA in delaminated carbon-epoxy composites when the repair process is thermally activated by heating induced with ultrasonic waves. It was discovered that bursts of short-duration, high frequency ultrasonic pulses were capable to thermally activating the healing process, and the healing efficiency (defined as recovery of mode I fracture toughness) was up to 130%. Multiple healing operations and full recovery to delamination toughness were achieved with ultrasonics. In addition to EMAA, the PhD project investigates the healing properties of other thermoplastics; namely PEGMA, EVA and ABS. The thermoplastics, except ABS, were capable of partially or completely restoring the delamination toughness and fatigue resistance of the composite. Healing with EMAA and PEGMA involved a pressure delivery mechanism whereas healing with EVA was controlled by its viscosity and adhesion properties. Through-the-thickness stitching with EMAA filaments on the delamination toughness and self-healing properties of carbon–epoxy composites was investigated. The delamination toughness and fatigue resistance of the composites increased with the volume content of EMAA stitches. During the healing these bridging stitches melt and flow into the delamination via the pressure delivery mechanism, and this resulted in full restoration of the toughness and fatigue properties. Multiple healing operations and full recovery to delamination toughness and fatigue resistance were achieved.
Degree Professional Doctorate
Institution RMIT University
School, Department or Centre 2014
Keyword(s) Polymer–matrix composites
PMC's
carbon fibre
delamination
fracture toughness
self-healing
thermoplastic resin
3-Dimensional reinforcement
stitching
mechanical testing
finite element analysis
FEA
mechanical properties
Versions
Version Filter Type
Access Statistics: 377 Abstract Views, 760 File Downloads  -  Detailed Statistics
Created: Fri, 11 Jul 2014, 13:21:26 EST by Lynne Johns
© 2014 RMIT Research Repository • Powered by Fez SoftwareContact us