D. H. Turkenburg; H. R. Fischer
Abstract
Internal microscopic damage is ubiquitous in composites, whether this was caused or introduced during the manufacturing process (i.e. via thermal stresses), from machining (i.e. drilling holes for bolted joints), during component assembly or ultimately from in-service loading. Incorporating an in-situ ...
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Internal microscopic damage is ubiquitous in composites, whether this was caused or introduced during the manufacturing process (i.e. via thermal stresses), from machining (i.e. drilling holes for bolted joints), during component assembly or ultimately from in-service loading. Incorporating an in-situ repair solution that can be activated after each of these individual processes could have a significant impact on reducing composite component scrappage rates, post-manufacture and other repairs and increase the time-period for non-destructive testing (NDT) inspection. By utilizing specific self-healing chemistries (i.e. via epoxy-amine polymers containing Diels-Alder based thermo-reversible bonds and/or epoxy resin healing agents) that can achieve multiple repair/healing cycles, damage generated throughout a components life cycle can be repaired and service life extended as well as complete recycling of fibers and resins can be possible. Materials of optimized composition form densely crosslinked networks at room temperature while repeatedly regaining the ability to flow at elevated temperature. Mechanical testing of bulk epoxy and reinforced polymer composite films demonstrated that the thermo-reversible effect is strong enough to achieve repetitive full self-healing of a severely cracked and delaminated test specimens without significantly affecting the mechanics of the resin. The resin has been integrated in prepreg based test specimen and the self-healing efficiency remained around 40% with 5 subsequent healing cycles. The embedded self-healing agents are thermally activated post-damage to repair the internal structure, akin to the healing functionality in animals and plants. This approach represents a truly positive benefit to industry to aid in the optimization of composite manufacture, by reducing post-manufacture inspection time and material wastage costs, and also to maximize the longevity of composite components in service as well as to introduce a true recycling possibility by recovery of the binder material system and of the reinforcing fibers.
Ikbal Choudhury; Sudipta Halder; Nazrul Islam Khan; Abhinav Mathur; Writuparna Nath; Aniruddha Phukan
Abstract
To deliver epoxy composites with enhanced self-healing ability, this study investigates healing efficiency of dual component epoxy system consisting of microcapsules containing epoxy (DGEBA) and different variants of hardener (TETA) microcapsules. Morphological investigation under FESEM confirms formation ...
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To deliver epoxy composites with enhanced self-healing ability, this study investigates healing efficiency of dual component epoxy system consisting of microcapsules containing epoxy (DGEBA) and different variants of hardener (TETA) microcapsules. Morphological investigation under FESEM confirms formation of spherical shaped intact TETA microcapsules at high agitation speed with average size of the ~65.32 µm and reduced wall thickness of ~1.823 µm. Reaction temperature is found to play significant role to tune the roughness of the microcapsule surfaces. The single edge notched bending (SENB) test was performed to evaluate the healing ability. It was found that with incorporation of microcapsules, the fracture toughness decreases but the healing efficiency increases with increase in content of microcapsules. The maximum healing efficiency observed was 65.61%. High concentration of TETA microcapsule (prepared at high agitation speed) in epoxy network gives the essence for their applicability as a potential ingredient to elevate the healing efficiency. To enhance the healing ability further of the composites as well as fibre reinforced composites with unaltered mechanical properties we believe synthesis nanocapsules and their incorporation could have significant impact.
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