The effects of particle size and silane treatment on the impact strength are experimentally evaluated for epoxy reinforced with nanometer- and micrometer-sized SiC particles. These nano and microcomposites are fabricated using two different sizes of SiC particles: 60–100 nm and 2–4 mm in diameter. The weight fraction of particles is fixed at 1.5% and the particles are dispersed using ultrasonication. For the purpose of investigating the effect of particle–matrix adhesion on the failure process, composites are fabricated using both as received and silane treated SiC particles and γ-aminopropyltriethoxysilane is used as an organofunctional coupling agent to control adhesion properties. Impact energy is measured using Frank IZod impact pendulum instrument. Additionally, fractured surfaces are observed under a scanning electron microscope to investigate particle bonding, particle dispersion, and toughening mechanism. Particle size along with dispersion and bonding are observed to affect the impact strength. It is observed that both the improved particle dispersion and bonding due to silane treatment lead to an increase in impact strength. With regards to particle size, the composites with nanometer-sized SiC particles are having greater impact strength compared to micrometer-sized particles.

In this study, an effort has been made to improve the mechanical, thermal, and ablation performance of carbon-phenolic (C-Ph) composites. The ZrO 2 , SiC, and ZrO 2 /SiC hybrid fillers were synthesized using sol-gel method followed by individual incorporation into C-Ph composites. The thermal stability and flexural strength of these C-Ph composites were analyzed using thermogravimetry analysis and three-point bending test, respectively. A significant improvement in the flexural strength and modulus of the reinforced C-Ph composites was observed and also exhibited the higher thermal stability. The oxyacetylene flame test was conducted to measure the ablation behavior of these filler reinforced C-Ph composites under a heat flux of 4.0 MW/m 2 for 60 seconds. ZrO 2 /SiC0.5 reinforcement in the C-Ph composite decreased the linear and mass ablation rates by 46% and 22%, respectively when compared with pure C-Ph composite. The surface morphology analysis revealed that the burnt composite covered with the ZrC ceramic phase and SiO 2 bubble-like structure, which could have improved the ablation resistance of composites. These results were found well within the acceptable range when using the surface energy dispersive spectroscopy and X-ray diffraction analysis. K E Y W O R D Sablation behavior, carbon fiber, flexural strength, nano silicon carbide, thermal stability

Stitched foam sandwich panel is a newly developed sandwich structure used in various structural applications. The sandwich skins are made of glass-fiber/epoxy-matrix composite; their interior layers are connected with glass yarn called piles. This paper investigates the effect of pile orientation on the shear strength of stitched foam sandwich panel. Four types of pile orientation are used; 90º, 45º, 90 º/45 º and 90º/45º/90º.The results are compared with a non-stitched sandwich panel. From the results of the core shear test, it is observed that the panels with 90º/45º/90ºorientation proved to be strongest among all.

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