PSI - Issue 41

Alok K. Srivastava et al. / Procedia Structural Integrity 41 (2022) 241–247 Alok K. Srivastava et al. / Structural Integrity Procedia 00 (2019) 000–000

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in agreement with the strong interfacial adhesion between fiber and the epoxy. Likewise, among longitudinal fracture surfaces in Fig. 5 (d, e, f), 0.4GNP laminate shows the largest amount of epoxy adhered on the fibers. The presence of GNPs in 0.2GNP laminate in Fig. 5g (indicated by yellow circle) can be seen which are adhered/mixed with the epoxy. Apparently, GNPs in 0.4GNP laminate (Fig. 5h) is not similar to former one and flakes of GNPs of different sizes can be seen in 0.4GNP laminate (indicated by yellow arrows) and a strong pull out of epoxy from the peripheral region (indicated by white dash line in Fig. 5h) of these GNP particles can be seen. The pull-out phenomenon of epoxy is ascribed to its higher mechanical interlocking with GNPs and this resulted in higher tensile strength and modulus of the 0.4GNP laminates. Consequently, the strong interfacial adhesion and larger interphase results in higher tensile properties of the GNP coated carbon fiber epoxy composites. Thus, the incorporation of the GNPs on the carbon fibers enhanced the tensile properties of the composites by interphase reinforcement.

Fig. 5. SEM micrographs of cross-sectional fracture surfaces of (a) Pristine, (b) 0.2GNP, (c) 0.4GNP laminates and longitudinal fracture surfaces (d) Pristine, (e, g) 0.2GNP, (f, h) 0.4GNP laminates 9. Conclusions In this work, GNPs were used as a nano-filler to coat the carbon fibers prior to laminate manufacturing through VARTM technique. Larger interphase was formed in GNP added laminates which implies enhanced interfacial interactions of GNPs with fibers and epoxy. Further, the laminates were tested under uniaxial tension and it was found that the GNP added laminates showed higher Young’s modulus as well as tensile strength compared to pristine laminates. This might be attributed to the larger interphase of the GNP added CFRPs. Further examination of the cross sections of the failed specimens showed larger debonding gaps between fiber and epoxy when no GNP were added. Also, at longitudinal fracture surfaces of pristine laminates, smooth and clean fiber surfaces can be seen which