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This study presents dynamic mechanical and impact properties of the new form of hybrid thermoplastic composites. The six composites of polyurethane/ p-aramid multiaxial fabric forms (Kolon fabrics) were impregnated with 10 wt% poly(vinyl butyral) (PVB)/ethanol solution with the addition of pristine multiwalled carbon nanotubes (MWCNT) where the PVB/fabric ratio was 20 wt%. All the composites consisted of four layers of the impregnated fabrics. The MWCNT/PVB content was 0, 0.5 and 1 wt%. The surface of the three composites with different MWCNT/PVB content was modified with γ-aminopropyltriethoxy silane (AMEO silane)/ethanol solution. The physical and dynamic mechanical properties of the prepared composite samples were analyzed by dynamic mechanical analysis (DMA) and high speed puncture impact tester. The structures of the composite samples were investigated by scanning electron microscopy (SEM). The results showed that the Kolon/AMEO/PVB/1 wt% MWCNT sample yielded a 60 % improvement in the storage modulus and a 73 % improvement in the impact absorbed energy compared to the Kolon/PVB sample. The carbon nanotubes (MWCNT) were added to improve the dynamic mechanical and impact properties of the materials for ballistic protection. [ABSTRACT FROM AUTHOR]

A study of high frequency fatigue in carbon-fiber reinforced composites has been undertaken. A comparison has been made between the fatigue behavior of crossply ($\backslash 0\; deg\; /\; 90\; deg$) and angleply ($\backslash plusmn\; 45\; deg$) carbon/epoxy unnotched and notched laminates. Additionally, a micromechanical analysis of fracture surfaces performed by scanning electron microscopy was carried out to evaluate the micromechanisms that occurred during fatigue. Experimental observations indicate that fatigue damage consists of a combination of matrix cracks, longitudinal splitting, fiber fracture, and delamination. In order to minimize the effects of residual strain due to temperature rise, a method is proposed for determining real fatigue strength at the level of variable load not lower than the fatigue limit, at which residual strains are minimal. [ABSTRACT FROM AUTHOR]