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Article Type

Original Study

Abstract

Structural integrity and service life of engineering components is based on fracture resistance. The paper presents an experimental study on the nano-additive that can be added to the locally-produced Iraqi engineering materials in order to enhance their fracture toughness. The research was inspired by the increasing demand in high-performance materials in the main sectors of the country such as infrastructure and energy besides the need to improve the properties of local resources. The tested material systems were two Portland cement composites and epoxy-based polymers. Nano-silica (n-SiO2 nano-alumina (n-Al2O3) and multi-walled carbon nanotubes (MWCNTs) were added to these matrices in different weight ratios (0.5% to 2.0%). Parameters of the fracture toughness including planestrain fracture toughness (K_Ic) and the J-integral (J_Ic) were established according to the ASTM E399 and ASTM E1820 guidelines. The experimental evidence proves that fracture toughness is improved significantly in the presence of nanoparticles. In the case of cement composites, addition of n-SiO2 in 1.5 wt.% resulted in the increase of K ic by up to 45%. MWCNTs loading of 0.5 wt.% increased J Ic by more than 70 in epoxy systems. Microstructural examination also indicated that the observed improvements were as a result of microstructural toughening processes, which include deflection of cracks, nanoparticles pull-out and bridging of microcracks. Such conclusions support the practical importance of nanotechnology in the improvement of the performance and reliability of engineering materials in Iraq, and provide a possible avenue towards lessening dependence on imported high-performance materials and improving the lifespan of national infrastructure.

Keywords

Fracture toughness, Nanocomposites, Cement, Epoxy, Iraqi materials, Experimental testing

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