Abstract

ABSTRACT

Investigation on the autonomic structural self-healing of FRPC using microencapsulated 5E2N/Grubbs catalyst system for low temperature applications


Mohammad Asgar Khan, Ph.D.
Concordia University, 2016

Structural self-healing of Fiber Reinforced Polymer Composites (FRPC) using microencapsulated 5E2N/Grubbs catalyst system is investigated in this work for low temperature applications. Microcapsule containing liquid 5E2N monomer in poly melamine urea formaldehyde (PMUF) shells have been synthesized following the in-situ polymerization technique. The effects of stirring speed and concentration of surfactant on the quality of microcapsules in terms of their average sizes, size distribution, surface morphology and shell thickness are investigated. An optimum combination of stirring speed-SLS concentration is established through numerous synthesis trials of microcapsules. The feasibility of self-healing with the current materials system is first demonstrated by visually observing the healing of crack network that is created on unreinforced epoxy samples impacted with high velocity projectiles. Different strength-based approaches like impact-heal-flexure, flexure-heal-flexure are examined to evaluate the self-healing performance of FRPC in the preliminary investigations. A fracture based approach based on the mode II delamination of FRPC which deals with determining material properties independent of geometry of samples is found to be a better choice for the evaluation of healing performance of FRPC. In the new proposed protocol, healing performance is evaluated by measuring and comparing the mode II fracture toughness of regular neat (not incorporated with healing agents) and modified (incorporated with healing agents) FRPC samples during the Non pre-cracked (NPC) and Pre-cracked (PC) test post healing without any manual intervention for achieving healing. Healing performance index, instead of healing efficiency, is defined by comparing the fracture toughness of regular and modified samples taking into account the possible toughening or weakening effect of incorporating healing agents into the composites. Healing performance index is shown to be a better and realistic indicator of actual healing performance than conventional healing efficiency definition. Effects of average size and concentration of microcapsules on the self-healing performance of FRP composites are investigated at room temperature using the proposed protocol. Finally, the effect of low temperature on self-healing performance of FRP composites is evaluated.