Effects of graphene nanoplatelets and graphene nanosheets on fracture toughness of epoxy nanocomposites

Abstract

The effects of graphene nanoplatelets (GPLs) and graphene nanosheets (GNSs) on fracture toughness and tensile properties of epoxy resin have been studied. A new technique for synthesis of GPLs based on changing magnetic field is developed. The transmission‐electron microscopy and the Raman spectroscopy were employed to characterize the size and chemical structure of the synthesized graphene platelets. The critical stress intensity factor and tensile properties of epoxy matrix filled with GPL and GNS particles were measured. Influence of filler content, filler size and dispersion state was examined. It was found that the GPLs have greater impact on both fracture toughness and tensile strength of nanocomposites compared with the GNSs. For instance, fracture toughness increased by 39% using 0.5 wt% GPLs and 16% for 0.5 wt% GNSs.

Improving the fracture toughness properties of epoxy using graphene nanoplatelets at low filler content

“…The aspect ratio of the f-GNPs used here was found to be 432, which is comparable to material used in previous studies, which ranged from 90 to 933. 9,[59][60][61] However it has been suggested that aspect ratios as high as 35 000 are needed for full stress transfer into the filler particles, [62][63][64] implying that the current system will not achieve optimized reinforcement. It was also noted that the presence of functional groups on the f-GNPs may improve the interfacial stress transfer.…”

“…For effective crack-pinning to occur, the reinforcing particles need to be larger than the crack-opening displacement. 59 Using an Irwin analysis to model the plastic zone, crack-opening displacement can be calculated. The maximum value in this work is found to be 3.4 μm for 0.25 wt% f-GNP loading.…”

Toughening mechanisms of nanoparticle-reinforced polymers

“…Carbon nanotubes (CNTs), carbon nanofibers, and graphene nanoplatelets (GPLs) are among the most frequent choices. Many studies concerning the effects of these rigid carbonic fillers on mechanical and fracture behavior of thermosetting polymers had reported a notable change in fracture resistance with lower filler contents in comparison with inorganic nanoparticles (Rafiee et al, 2009;Zhou et al, 2007Zhou et al, , 2008Shokrieh et al, 2014b). Figure 11.2 represents the increase in fracture toughness and fracture energy of an epoxy matrix with incorporation of GPLs (Shokrieh et al, 2014b).…”

Graphene-Based Polymer Nanocomposites: Chemistry and Applications

“…It was found that the graphene nanoplatelets have greater impact on both fracture toughness and tensile strength of nanocomposites than graphene nanosheets. Optimal improvement was observed in critical stress intensity factor and Young's modulus for 0.5 wt% graphene nanoplatelet epoxy with an average increase compared with neat epoxy of about 39 and 15 %, respectively [120]. The glass transition temperature of neat epoxy increased from 94.7 to 108.6°C with 2.5 wt% modified graphene, which had been produced through grafting 4,4′-methylene diphenyl diisocyanate into graphene platelets [176].…”

“…Results clearly demonstrated a significant increase on the mechanical performance of the hybrid films, probably due to interaction between the graphene platelets and the polymeric chains, consequently increasing T g values and toughness. Recently, Shokrieh et al [120] investigated the effects of graphene nanoplatelets and graphene nanosheets on the fracture toughness and tensile properties of epoxy resin. It was found that the graphene nanoplatelets have greater impact on both fracture toughness and tensile strength of nanocomposites than graphene nanosheets.…”