Electrospun thermoplastic-thermosetting resin for hindering delamination and possibly self-healing in laminate CFRPs.
Topic(s) : Multifunctional and smart composites
Co-authors :
Emanuele MANZI (ITALY), Pietro BRAGA (ITALY), Emanuele MACCAFERRI (ITALY), Laura MAZZOCCHETTI (ITALY), Tiziana BENELLI (ITALY), Tommaso Maria BRUGO (ITALY), Andrea ZUCCHELLI (ITALY), Loris GIORGINI (ITALY), Giulia LUCARINIAbstract :
Polymer matrix composites (PMCs), and in particular carbon fiber reinforced polymers (CFRPs), possess many outstanding properties, including lightweight, high strength-to-weight ratio and excellent mechanical properties, that make them ideal candidates as replacements for metals in many structural applications [1]. However, composite materials that possess a laminar structure suffer from some intrinsic weaknesses, including poor delamination resistance, resulting in high susceptibility to impacts and vibrations, which is the most severe drawback that limits the widespread application of high-performance fiber-reinforced polymer (FRP) laminates [2,3]. The reduction of the risk of delamination, besides increasing safety, can even extend the service life thus promoting the component’s sustainability, making it a crucial topic.
Several possible remedies to hinder delamination have been proposed, including the interleaving of nonwoven nanofibrous mats. Common thermoplastic polymers, such as poly(ε-caprolcatone) and polyamides (Nylons) [3] and, more recently, even rubbery nanofibers [4,5] have been electrospun and successfully integrated into epoxy CFRP laminates, providing significant interlaminar fracture toughness enhancement. At the same time, studying systems that act 'downstream’ once delamination has occurred could be interesting. Within this context, self-healing systems allow total or partial recovery of the laminate's initial mechanical characteristics [6]. In this frame, a smart solution could consist in the use of interleaved mats able to provide self-healing capability without compromising the initial mechanical properties of the laminate.
The present study aims at illustrating a preliminary evaluation of the properties of a resin that displays both thermoplastic and thermosetting behaviour, with a focus on understanding whether the obtained electrospun mats have a beneficial effect on the laminate’s mechanical properties or not and assess its possible self-healing ability, exploiting its peculiar thermal behaviour. Indeed, this particular resin possesses a thermoplastic behaviour at low temperatures, with a glass transition temperature (Tg) just above room temperature, thus allowing an easy electrospinning procedure and general processability, avoiding any coalescence phenomena, in a similar fashion to common thermoplastic polymers. Instead, the thermosetting behaviour, exploitable for enabling self-healing, is triggered at higher temperatures, when the crosslinking reaction occurs. The modified laminates show increased interlaminar fracture toughness both in Mode I and Mode II (up to 2 times for Mode II), thus confirming the beneficial effect of the nanofibrous interleave, and opens the possibility to investigate the self-healing ability of the resin.
Several possible remedies to hinder delamination have been proposed, including the interleaving of nonwoven nanofibrous mats. Common thermoplastic polymers, such as poly(ε-caprolcatone) and polyamides (Nylons) [3] and, more recently, even rubbery nanofibers [4,5] have been electrospun and successfully integrated into epoxy CFRP laminates, providing significant interlaminar fracture toughness enhancement. At the same time, studying systems that act 'downstream’ once delamination has occurred could be interesting. Within this context, self-healing systems allow total or partial recovery of the laminate's initial mechanical characteristics [6]. In this frame, a smart solution could consist in the use of interleaved mats able to provide self-healing capability without compromising the initial mechanical properties of the laminate.
The present study aims at illustrating a preliminary evaluation of the properties of a resin that displays both thermoplastic and thermosetting behaviour, with a focus on understanding whether the obtained electrospun mats have a beneficial effect on the laminate’s mechanical properties or not and assess its possible self-healing ability, exploiting its peculiar thermal behaviour. Indeed, this particular resin possesses a thermoplastic behaviour at low temperatures, with a glass transition temperature (Tg) just above room temperature, thus allowing an easy electrospinning procedure and general processability, avoiding any coalescence phenomena, in a similar fashion to common thermoplastic polymers. Instead, the thermosetting behaviour, exploitable for enabling self-healing, is triggered at higher temperatures, when the crosslinking reaction occurs. The modified laminates show increased interlaminar fracture toughness both in Mode I and Mode II (up to 2 times for Mode II), thus confirming the beneficial effect of the nanofibrous interleave, and opens the possibility to investigate the self-healing ability of the resin.