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.
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