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Abstract. This study investigates the effects of nano carboxylic acrylonitrile butadiene rubber (CNBR-NP) and nano acrylonitrile butadiene rubber (NBR-NP) on the interlaminar shear strength and fracture toughness of carbon fibre reinforced polymer composites (CFRP) with dicyandiamide-cured epoxy matrix. The results show that nano-size dispersion of rubber significantly improved the Mode I delamination fracture toughness (GiC) of the CFRP by 150% and its Mode II delamination fracture toughness (G[IC) by 80% with the addition of 10 phr of CNBR-NP. For the NBR-NP system, the GIC and GIIC delamination fracture toughness of the CFRP were increased by 100 and 80% respectively with the addition of 10 phr (parts per hundred rubber) of nano rubber to the matrix. Scanning electron microscopy (SEM) images of the fracture surface revealed that the toughening was mainly achieved by debonding of the nano rubber, crack path deflection and fibre bridging.
Keywords: polymer composites, processing technologies, nanomaterials, mechanical properties, nanocomposites
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1.Introduction
Carbon fibre reinforced polymer composites (CFRP) are widely used in advanced engineering technologies. Epoxy resins are employed as their matrix material, possessing outstanding mechanical performance and good processability. However, epoxy resins are relatively brittle which causes a major problem for the engineering performance of the final structure. To overcome this weakness, scientists have been toughening the formulations with nano and micron-scale particles in the last three decades.
Several research teams have explored the modification of the properties of epoxy resins by introducing various toughening agents such as reactive liquid rubber [1], thermoplastics [1, 3], micron scale rubber particles, nano rubber particles [4, 8], and nanoscale fillers [5, 6]. One of the main objectives behind the modification of the epoxy is to improve the fracture toughness of the resin without sacrificing intrinsic properties like the glass transition temperature (Tg) and its elastic modulus. A significant increase in the fracture toughness of advanced composite laminates can constitute a potential route towards designing composites with an extended lifetime and durability.
Recent studies have demonstrated the benefits of using nanoparticles to improve the mechanical properties of epoxy resins. Tang et al. [7] reported a 52% increase in the KIC of epoxy resin with 0.2 wt% highly dispersed thermally reduced graphene sheets addition. Qi et al. [8] observed an improvement of...