Abstract
In the present investigation, thermo-reversible bonds formed between maleimide and furan groups (Diels–Alder (DA)-based bis-maleimides (BMI)) have been generated to enable high-performance unidirectional (UD) carbon fiber-reinforced plastics (CFRPs) with self-healing (SH) functionality. The incorporation of the SH agent (SHA) was performed locally, only in areas of interest, with the solution electrospinning process (SEP) technique. More precisely, reference and modified CFRPs with (a) pure SHA, (b) SHA modified with multi-walled carbon nano-tubes (MWCNTs) and (c) SHA modified with graphene nano-platelets (GNPs) were fabricated and further tested under Mode I loading conditions. According to experimental results, it was shown that the interlaminar fracture toughness properties of modified CFRPs were considerably enhanced, with GNP-modified ones to exhibit the best toughening performance. After the first fracture and the activation of the healing process, C-scan inspections revealed, macroscopically, a healing efficiency (H.E.) of 100%; however, after repeating the tests, a low recovery of mechanical properties was achieved. Finally, optical microscopy (OM) examinations not only showed that the epoxy matrix at the interface was partly infiltrated by the DA resin, but it also revealed the presence of pulled-out fibers at the fractured surfaces, indicating extended fiber bridging between crack flanks due to the presence of the SHA.
Highlights
Fiber-reinforced polymer composites (FRPs) are leading candidates as component materials to improve the efficiency and sustainability of many forms of transport due to their lightweight, high specific-strength and stiffness values
Non-autonomous SH technology has been demonstrated through self-healable polymers that are based on supramolecular chemistries [8,9,10,11], covalent bonding [12,13,14] and special covalent bonding (i.e., Diels–Alder (DA)based mechanism bis-maleimide (BMI) polymers) [15,16]
The self-healing agent (SHA) reactants were dissolved into THF solvent in the amount of 15 wt% to fabricate the electrospun solution, with the aim to integrate it into the composite structure by solution electrospinning process (SEP) [19]
Summary
Fiber-reinforced polymer composites (FRPs) are leading candidates as component materials to improve the efficiency and sustainability of many forms of transport due to their lightweight, high specific-strength and stiffness values. An emerging approach called “Self-healing (SH) materials” has been proposed but has not yet been applied to commercial composites [2] This smart technology aims to repair damages in situ and autonomously, leading to an extension of the effective life-span of the composite structures. Non-autonomous SH seems to be the most promising approach for SH composites, as specific reversible bonds are introduced into epoxide networks [5,6,7] This approach allows the healing to be unlimited as no chemicals are consumed, if compared with the autonomous SH mechanism (capsuleor vascular-based network) [4]. In [18], the authors investigated the effect of SHA concentration and curing cycle of DA-based CFRPs on mechanical and healing performance. Three-point bending tests (3PB) were performed to investigate the effect of the SHA on the in-plane mechanical properties of the CFRP, while optical microscopy (OM) examinations of cross-sections and fractured surfaces were performed to investigate the involved failure mechanisms
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