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Three‐point flexural fatigue behaviour and mode I interlaminar fracture toughness of the carbon fibre reinforced polymer composites (CFRPCs) modified by the addition of graphene nanoplatelet (GnP) were investigated. CFRPCs without any addition of nanoparticles were also tested as control samples. Fatigue life was characterized by the two parameter Weibull distribution function and predicted using the combined Weibull and Sigmoidal model. It was found that incorporation of very small amount (0.1%) of GnP in the epoxy polymer matrix improved mean and predicted fatigue life up to 155% and 190% (0.5 failure probability), respectively. The critical mode I interlaminar fracture toughness of the GnP reinforced composites was found up to 40% higher than the control samples. The improvement achieved by incorporating GnP is discussed in terms of crack deflection mechanism by nanoparticles and scanning electron micrograph images of the fracture specimens that revealed strong interfacial bonding in the nanoreinforced specimens.

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This paper presents the study of repeatable self-healing capability of thermoplastic healing agent poly-caprolactone (CAPA-6506) and shape memory polymer (SMP) in a fiber reinforced polymer composite structure. This self-healing is inspired by the bio-mimetic process of ‘close then heal’ mechanism where the thermally actuated SMP causes the closing of cracks and the thermoplastic healing agent performs the healing. In this study, two types of sixteen layered unidirectional carbon fiber reinforced thermoset polymer (SC-780) composites were tested: (1) with SMP (containing 6.4 vol% of CAPA and 0.6 vol% of SMP), and (2) without SMP (containing 6.4 vol% of CAPA only). To quantify the healing efficiency in terms of Mode-I interlaminar fracture toughness, double-cantilever beam tests were carried out for seven separate healing cycles by following the ASTM-D5528-13 standard. The tests yielded promising results as maximum healing efficiency of 73%, and 63% were achieved for with SMP and without SMP specimens, respectively. In addition, increased surface roughness due to the crack deviation, SMP pullout, SMP and CAPA bridging between the layers, and plastic deformation of the matrix that are responsible for crack growth resistance were observed during fractography analysis. Also, the relationships between the composition and material properties of epoxy and healants were thoroughly investigated via Fourier transform infrared (FTIR) spectra and differential scanning calorimetry (DSC).

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