Unidirectional (UD) pre-pregs containing self-healing materials based on Diels-Alder reaction bis-maleimide (BMI) polymers were successfully incorporated on the mid-plane of UD carbon fibre reinforced polymers. The fracture toughness of these composites and the introduced healing capability were measured under mode I loading. The interlaminar fracture toughness was enhanced considerably, since the maximum load (P max ) of the modified composite increased approximately 1.5 times and the mode I fracture energy (G IC ) displayed a significant increase of almost 3.5 times when compared to the reference composites. Furthermore the modified composites displayed a healing efficiency (HE) value of about 30% for P max and 20% for G IC after the first healing, appearing to be an almost stable behaviour after the third healing cycle. The HE displayed a decrease of 20% and 15% for P max and G IC values, respectively, after the fifth healing cycle. During the tests, the monitored acoustic emission (AE) activity of the samples showed that there is no significant difference due to the presence of BMI polymer in terms of AE hits. Moreover, optical microscopy not only showed that the epoxy matrix at the interface is partly infiltrated by the BMI polymer, but it also revealed the presence of pulled out fibres at the fractured surface, indicating ductile behaviour.

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Abstract. This study focuses on the transfer of the healing functionality of supramolecular polymers (SP) to fibre reinforced composites through interleaving. SPs exhibiting self-healing based on hydrogen bonds were formed into films and were successfully incorporated into carbon fibre composites. The effect of the SP interleaves on in-plane fracture toughness and the subsequent healing capability of the hybrid composites were investigated under mode II fracture loading. The fracture toughness showed considerable increase since the maximum load (P max ) of the hybrid composite approximately doubled, and consequently the mode II interlaminar fracture toughness energy (G IIC ) exhibited an increase reaching nearly 100% compared to the reference composite. The healing component was activated using external heat. P max and G IIC recovery after activation were measured, exhibiting a healing efficiency after the first healing cycle close to 85% for Pmax and 100% for G IIC , eventually dropping to 80% for P max while G IIC was retained around 100% even after the fourth healing cycle. Acoustic Emission activity during the tests was monitored and was found to be strongly reduced due to the presence of the SP.

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Self‐healing resin (Bismaleimide prepolymer, BMI pp) based on Diels–Alder reaction mechanism was integrated into high performance carbon fiber reinforced plastics (CFRPs). Reference and BMI pp modified CFRPs were manufactured by incorporating grains of the self‐healing agent (SHA) in the mid‐thickness interlaminar region through sieving. First, the effect of the SHA concentration on the toughening and healing performance of CFRPs was studied under mode I fracture loading. The SHA was able to enhance the interlaminar fracture toughness of the composite to a certain extent and also to offer a moderate thermally activated healing functionality. Also, the effect of the curing temperature on the same results was studied; it was found the decrease of the curing temperature slightly decreases the fracture toughness while increases the healing efficiency of the composite. Finally, optical microscopy examinations were conducted and three‐point bending tests were utilized to study the in‐plane mechanical properties of the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47478.