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Nano-microscale fracture mechanisms, which affect fracture toughness, play an important role in improving the impact characterization of fiber reinforced polymer composites. Therefore, crack behaviors are tried to be controlled with fracture mechanisms by filling nanoparticles into polymer matrix for improving impact characteristics and fracture toughness in latest studies. In this study, it was aimed to investigate the effects of SiO2 nanoparticles addition into epoxy matrix on the low velocity impact characteristics and fracture toughness in basalt fiber reinforced filament wound composite tubes. SiO2 nanoparticle of 4% wt. filled and unfilled ± [55]6 filament wound basalt fiber reinforced/epoxy composite tubes were subjected to low velocity impact tests at 5 J, 10 J, and 15 J of energy levels. It was seen that while the addition of nanoparticles were increasing the maximum impact forces in the range of about 19%–32%, displacements and absorbed energies decreased because of the increase in the bending stiffness. Charpy impact tests were performed to three different notched arc shaped specimens for determining the impact fracture toughness. SiO2 nanoparticles increased the fracture toughness by 20%–23%. It was observed that SiO2 nanoparticles delayed the formation of failures such as debonding and delamination, and reduced the fiber breakage branching in low velocity impact tests. A liquid penetrant test was used to inspect the crack formations and progressions on the impacted surfaces of all composite tubes as practical inspection for industrial applications. It was seen that microscope and SEM analysis supported the liquid penetrant inspection, which is a non-destructive testing method.

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In general the nanoparticles increase the mechanical and impact behaviors of fiber reinforced polymer based composites. However, the effects of the hybridization of nanoparticles and their reasons over the nano scale fracture mechanisms have not been adequately studied for fiber reinforced composites. In this study, the low velocity impact responses and the mechanical behaviors were investigated for 4%wt. SiO2 nanoparticles filled BFR/Epoxy nanocomposites, 0.5%wt. MWCNTs filled BFR/Epoxy nanocomposites, 4%wt. SiO2 nanoparticles and 0.5%wt. MWCNTs nano-hybrid filled BFR/Epoxy nanocomposites and unfilled BFR/Epoxy composites. The tensile and low velocity impact tests at 10 J and 20 J of energy levels were applied to nanoparticles, nano-hybrid and unfilled BFR/Epoxy composites in order to define the effects of nanoparticles and nano-hybrid particles on the impact and mechanical features according to in accordance with ASTM D3039/D3039M-14 and ASTM D7136/7136M standards. It was observed that SiO2 nanoparticles addition to BFR/Epoxy for both 10 J and 20 J showed the highest tensile strength, maximum force, rebound energy and the lowest displacements and absorbed energy. SiO2+MWCNTs nano-hybrid addition to BFR/Epoxy improved higher low velocity impact responses and tensile strength than MWCNTs addition. The specimens of unfilled BFR/Epoxy composites showed the lowest tensile strength and maximum force and the highest maximum force, displacements and absorbed energy. Microscope and SEM analyses demonstrated that minimum failures like fiber breakages, delamination and debonding were observed by filling SiO2 nanoparticles provided the nano scale fracture mechanisms. In addition MWCNTs hybridization with SiO2 nanoparticles minimizes negative effects of MWCNTs micro size length and improved the impact and mechanical behaviors.