Fatigue behaviour of open-hole carbon fibre/epoxy composites containing bis-maleimide based polymer blend interleaves as self-healing agent

Bis-maleimides (BMIs) exhibit healing functionalities on polymer level. In the current investigation, BMI self-healing (SH) resin based on Diels-Alder (DA) reaction mechanism (identification code: BMI pp) was integrated into high performance aerospace carbon fiber reinforced plastics (CFRPs). The effect of BMI pp as self-healing agent (SHA) into CFRPs is assessed. More precisely, open-hole reference and BMI pp modified CFRP samples having [45/-45/0/90](2S) stacking sequence, with similar fiber volume fractions have been tested under quasi static tensile and tension-tension fatigue loading conditions. According to quasi static experimental results, it was shown that the incorporation of the BMI pp SHA did not deteriorate the in-plane mechanical properties of the entire composite. In addition, tension-tension fatigue tests revealed that the incorporation of the BMI pp SHA into composites architecture made composites to slightly extend their fatigue life. Finally, the activation of the healing functionality of BMI pp modified composites at certain number of fatigue cycles significantly extends their fatigue life of about 75%. For all fatigue tested material sets a three-stage pattern of stiffness degradation was observed.