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The aim of this study was to research the effect of carbon nanofiber (CNF), the microballoon (MB) volume fraction and its density on both the vibration properties and impact behavior of carbon nanofiber – reinforced syntactic foam. Twelve different types of syntactic foam were produced with two different CNF contents, two different MB densities and two different MB volume fractions. Neat epoxy, syntactic foams with and without carbon nanofiber were manufactured for characterization by comparing each other in terms of mechanical and dynamic properties. With the free vibration tests, natural frequencies and damping ratios were investigated. Besides vibrations tests, low-velocity impact and tensile tests were conducted on the syntactic foams. Analyses of the results were performed on the effect of the volume fraction of additives and MB density on the vibration, impact and tensile behavior of the syntactic foams. In addition, SEM was used to understand the microstructure of the samples tested. Vibration results presented that the presence of carbon nanofiber enhanced strength but was not effective on damping, while low-velocity impact, and tensile test results also demonstrated the same trend. [ABSTRACT FROM AUTHOR]

Vapor grown carbon nanofibers (VGCF) were dispersed throughout phenylethynyl terminated polyimide 'Triple A PI (TriA-PI)'. TriA-PI is a newly developed thermosetting polyimide, and the cured polymer exhibits excellent mechanical properties and high glass transition temperature (Tg > 300°C). The resulting composites containing 0, 3.2, 7.7, and 14.3 wt% of VGCFs exhibited relatively good dispersion in macroscopic observations. Dynamic mechanical analysis (DMA) showed an increase in Tg with incorporation of VGCFs; however, increase in Tg was not pronounced compared to multi-walled carbon nanotube (MWNT) dispersion. The experimental result suggested that the VGCFs and MWNT are immobilizing the polyimide chains at elevated temperature, and the chemical and physical interactions between nanofibers and the polyimide are governed by the surface area of the nanofibers per unit volume in composites. [ABSTRACT FROM AUTHOR]