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The effect of different weight percentages (wt.%) of MWCNTs includes 0, 0.17, 0.34 and 0.51% on the mechanical and low-velocity impact properties are presented on the example of the pure epoxy and epoxy/fiberglass composites beams. A sonication technique is used to disperse MWCNTs in the epoxy network and the nanocomposite beams are fabricated using hand lay-up technique. In tensile tests, the value of Young’s modulus, tensile strength and strain at break are reported. In the low-velocity impact tests on the MWCNTs/fiberglass/epoxy, the time-history response of contact force, displacement and velocity of the impactor and indentation and displacement of the beam are measured and presented. The results show that compared to pure epoxy, Young’s modulus and tensile strength of epoxy/MWCNTs are increased 21.98% and 58.32% at 0.34 wt.% of CNTs, respectively, and raised 1.05 and 1.17 times at 0.17 wt.% of CNTs for the epoxy/fiberglass/MWCNTs, respectively. It is observed that the excellent improvement in the impact properties is achieved for 0.34 wt.% of CNTs. A series of polynomial formulations as a function of wt.% of CNTs are proposed to calculate the Young’s modulus, peak contact force and maximum beam deflection at the impact position.

In this article, a new analytical model is presented for low velocity impact on an axially functionally graded (AFG) carbon nanotube (CNT) reinforced cantilever beam. In order to estimate the material properties of the composite media, the refined rule of mixtures approach containing the efficiency parameters is employed. Based on the third order shear deformation beam theory, the beam deformation is formulated and the contact force is obtained with the aid of the nonlinear Hertz contact law. To derive the equations of motion, energy method with combining the polynomial Ritz method and generalized Lagrange equations are employed. To validate the accuracy of the analytical model, the convergence and comparison studies are carried out with those are reported in the literature in the special cases and simulating the process with ABAQUS software. Afterward, the influences of CNTs distribution, CNTs volume fraction, impact position, impactor initial velocity, and beam geometrical parameters on the contact force and beam deflection at the impact position are studied in detail. POLYM. COMPOS., 39:E969–E983, 2018. © 2017 Society of Plastics Engineers

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In this paper, the effect of addition of nanosilica on mechanical properties of pure epoxy and epoxy/fiberglass composite has been investigated. The epoxy/nanosilica composites and epoxy/fiberglass/nanosilica hybrid composites have been fabricated, and the Young’s modulus, tensile strength, yield stress and elongation at break have been determined by simple extension tests. The results show that by addition of 1 wt% of nanosilica in both types of composites, Young’s modulus, yield stress and tensile strength decrease and elongation at break increases. By increasing the nanosilica content, the Young’s modulus, yield stress and tensile strength increase and elongation at break decreases. Also, imperialist competitive algorithm is employed to model the mechanical properties as fourth degree polynomial functions. The accuracy of polynomial is maximized and coefficients are obtained. The results show 25.66%, 56.87% and 45.84% improvement in Young’s modulus, yield stress and tensile strength of pure epoxy, respectively. Also, 12.9%, 24.83% and 12.85% improvement in Young’s modulus, yield stress and tensile strength of epoxy/fiberglass composites, has been observed, respectively.

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