Relevance of graphene oxide as nanofiller for geometrical variation in unidirectional carbon fiber/epoxy composite

Abstract

Curved geometry in unidirectional CFRP (UD‐CFRP) demands ideal shape optimization to attain superior performance while maintaining the desired high strength to weight ratio. Herein, the effect of graphene oxide (GO) as the potential filler to improve the mechanical and thermal properties of flat and curved specimens of UD‐CFRP was investigated. The GO was synthesized using Hummer's method and introduced in the epoxy resin by wet transfer technique. Three‐point and four‐point bending analysis of UD‐CFRP showed maximum flexural strength and modulus at 0.3 wt% GO addition in UD‐CFRP. The improved interfacial adhesion of 0.3 wt% GO incorporated UD‐CFRP was realized by calculating storage modulus, reinforcement efficiency factor (r), C‐factor, adhesion factor, cross‐linking density, and glass transition temperature (Tg) from dynamic mechanical analyzer. Fracture analysis by scanning electron microscope showed the superior interlocking in carbon fiber, and epoxy polymer at 0.3 wt% GO addition.

In situ cross‐linking capability of novel amine‐functionalized graphene with epoxy nanocomposites

“…The degree of oxidation in GO is calculated by O1s spectra, where majorly three peaks can be fitted at 532.0, 532.8, and 533.5 eV, and they signify the presence of hydroxyl/epoxide oxygen, carbonyl oxygen, and carboxylic oxygen, respectively (Figure 3b). 41,45 For GO COOH, C1s spectra are fitted with five peaks as observed in GO (Figure 3c). In the case of GO COOH, mild oxidation resulted in an increment of oxygen content (Figure 3d).…”

“…As done in our previous study, the epoxy nanocomposites were fabricated via the solvent casting method. 45 All synthesized graphene material was incorporated in epoxy polymer by the three-way dispersion method. Initially, functionalized graphene was dispersed in ethanol using a bath ultrasonicator for 2 h followed by high shear of homogenization for 1 h. In the second step, dispersed graphene was transferred to epoxy resin, and the solvent was evaporated at 80 C for 24 h. In the last step, the graphene-epoxy mixture was homogenized by high shear homogenizer for 1 h at 80 C. The functionalized graphene content was varied in epoxy resin from 0.1 to 0.4 wt%, and 25 wt% of hardener HY5200 was added to the epoxy mixture and degassed in a vacuum desiccator for 1 h. The mixture of graphene-epoxy and hardener was transferred to the mold die of the desired shape and cured at temperature 120 C for 4 h followed by postcuring at 160 C for 2 h.…”

“…SAED pattern of GO (Figure 4b) shows the diffused ring structure in the electron diffraction pattern, which signifies the highly amorphous nature of GO. 45 The structure of GO COOH also contains folded structure, but the degree of entanglement is low compared with GO. The mild oxidation by monochloroacetic acid rearranges the structure to higher stability than GO (Figure 4c).…”

“…It might be possible that the linkage between the epoxy and GO CONHCH 2 CH 2 NH 2 is not physical as it was observed for GO and GO COOH (shown in a previously reported study). 45,63 One of the reasons for increment strength is effective stress transfer, which depends on the inter-molecular adhesion between polymer and nanofillers. 63 The lower decrement in flexural strength for GO CONHCH 2 CH 2 NH 2epoxy nanocomposite at 0.4 wt% indicates the formation of a strong chemical bond between GO CONHCH 2 CH 2 NH 2 and epoxy polymer.…”

“…43,44 In previously reported work, GO was incorporated in epoxy polymer to improve the interfacial strength of epoxy nanocomposite, and the formation of additional H-bonding between GO and epoxy polymer is confirmed. 45 However, in the noncovalent interaction such as H-bonding, weak van der Waals, or π-π interactions between GO and epoxy polymer, the enhancement of the mechanical and thermal properties is limited up to a specific value. The performance of epoxy nanocomposite can be further improved by introducing a covalent chemical bond between the epoxy polymer and graphene.…”