In recent years, the industry has adopted self-healing coatings that rely on embedded microcapsules filled with reactive liquid chemistries upon a surface scratch, the liquid healing agents-released from the ruptured capsule core-polymerize to restore the protective coating 21. However, in situ self-healing FRP composites-that can recover repeatedly from structural-scale damage-have yet to transcend research laboratories 18, 19, 20. Over the last twenty years, self-healing polymers and composites have emerged, offering an autonomous route to mitigate deterioration and prolong useful lifetime 14, 15, 16, 17. It is, therefore, prudent to embrace and realize synthetic structural systems that mimic living organisms’ evolutionary healing attributes of in situ and continual self-repair. Coupled with high energy demands from manufacturing 12 and growing supply chain shortages for petrochemicals used to produce polymer products 13, the need to extend the useful lifetime of FRP materials is now greater than ever. The dwindling supply of non-renewable natural resources, adverse climatic effects from production-related pollution 8, difficulty in recycling spent thermoset-matrix materials 9, and already pervasive plastic pollution 10 make a strong environmental case for finding alternatives to FRP component replacement 11. Moreover, the widespread replacement of FRP is not sustainable from environmental and economical standpoints.
#Composite preform manual
These defects at the micron-scale can develop into large-scale damage and, if unaddressed, may lead to catastrophic failures.Įven upon locating internal damage, manual repair of FRP composites is costly, laborious, and not always successful 7. However, such hierarchical FRP composites are prone to complex, multi-scale damage modes 3, 4 (e.g., matrix cracking and interlaminar delamination) that are difficult to detect using current nondestructive evaluation (NDE) or structural health monitoring (SHM) techniques 5, 6. Fiber-reinforced polymer (FRP) composites-proven transformative in the aerospace industry-are modern materials replacing conventional constituents (e.g., metals) for superior strength- and stiffness-to-weight ratios and enhanced durability in corrosive environments. However, such a design paradigm is not always practical nor achievable: conservative designs can lead to bulky structures, and structural systems invariably encounter unexpected conditions over a long operating lifetime. Consequently, they are often over-engineered to prevent failure. Traditional synthetic material systems, on the other hand, lack the ability to self-repair. Bereft of in situ and sustained repair, a benign cut could exacerbate and prove fatal. For instance, upon laceration in healthy human skin, healing begins instantly and continues until restoring necrotic with new tissue-without hindering other body functionalities 2. (ii) Sustained: the healing functionality persists even after many damage/repair cycles (i.e., throughout an organism’s life). The success of biological healing stems from two essential attributes: (i) In situ: an innate capacity to deliver healing agents to the injured site and self-repair the damage in place. The ability to heal and recover from minor injuries is vital for living organisms 1. The marked lifetime extension offered by this self-healing strategy mitigates costly maintenance, facilitates repair of difficult-to-access structures (e.g., wind-turbine blades), and reduces part replacement, thereby benefiting economy and environment. A discovery of chemically driven improvement in thermal remending of glass- over carbon-fiber composites is also revealed.
#Composite preform full
Full fracture recovery occurs below the glass-transition temperature of the thermoset epoxy-matrix composite, thus preserving stiffness during and after repair. By 3D printing a mendable thermoplastic onto woven glass/carbon fiber reinforcement and co-laminating with electrically resistive heater interlayers, we achieve in situ thermal remending of internal delamination via dynamic bond re-association. Here we transcend existing obstacles and report a fiber-composite capable of minute-scale and prolonged in situ healing - 100 cycles: an order of magnitude higher than prior studies.
Overcoming these inherent challenges for mechanical self-recovery is vital to extend in-service operation and attain widespread adoption of such bioinspired structural materials. But sustained in-service repair of structural fiber-reinforced composites remains unfulfilled due to material heterogeneity and thermodynamic barriers in commonly cross-linked polymer-matrix constituents. An emerging class of synthetic self-healing polymers and composites possess property-retaining functions with the promise of longer lifetimes.
Natural processes continuously degrade a material’s performance throughout its life cycle.
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