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The effects of multi-walled carbon nanotubes (MWCNTs) and nanosilica on tensile behavior of woven carbon fabric-reinforced epoxy composites have been studied. Multi-scale composites with epoxy matrices modified with different MWCNT and nanosilica contents (0.1, 0.5 and 0.9 wt.%) have been fabricated by vacuum-assisted resin infusion molding (VARIM). The dispersion of the nanoparticles in the epoxy resin has been made using an ultrasound and high-speed shearing method. Incorporation of nanoparticles improved tensile behavior and this effect was more evident in the case of composites reinforced with 0.5 wt.% of MWNCT and nanosilica. Incorporating either of the tow nanoparticles at 0.9 wt.% leads to a decrease in the trend of tensile properties. Examination of fracture surfaces using scanning electron microscopy (SEM) showed that by incorporating 0.9 wt.% of each nanoparticle, there are local MWCNT and nanosilica agglomerations within the composites. These nanoparticle-agglomerates reduced their potential strengthening effect in multi-scale composites containing 0.9 wt.% of nanoparticles. Also, SEM images showed that the MWCNTs and nanosilica enhanced the fiber–matrix interfacial strength and then by toughening the surrounding matrix, improved the strength and stiffness of multi-scale composites.

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The first aim of this paper is to experimentally explore the effect of multi-walled carbon nanotubes (MWCNTs) on the coefficient of thermal expansion (CTE) of epoxy-based composites. Focusing on the obtained experimental data, two important conclusions can be drawn. 1) Though the CTE of carbon nanotubes (CNTs) is lower than that of neat epoxy, using more CNT does not necessarily decrease the CTE of epoxy polymer. 2) The optimum weight percent of CNT is 0.3 which can reduce the CTE of epoxy up to 33%. As the second goal of the present research work, thermal buckling analysis of rectangular carbon fiber-reinforced CNT/epoxy polymer (CFRCNTEP) laminated composite plates is performed numerically. To this purpose, first, using the obtained experimental data and micro-mechanical models, the thermo-elastic properties of structure are calculated. Then, based on the first-order shear deformation theory (FSDT) and by means of generalized differential quadrature (GDQ) method, the influence of CNTs on the critical buckling temperature of CFRCNTEP composite plates is investigated. The numerical results reveal that MWCNTs can strongly affect thermal buckling behavior of composite plates. It is observed that by adding 0.3 wt% CNTs into the matrix phase, the critical buckling temperature increases between 35 to 42%.