The energy absorption capacity of a series of axially crushed composite tubes fabricated from high tow count graphite fiber is compared with those of similar tubes fabricated from aerospace-grade fiber to determine the viability of considering the use of such fibers in automotive applications. To that end, graphite-epoxy tubular specimens with circular and square cross-sectional geometries; stacking sequences with ±45° fibers and with both ±45° and 0° fibers; and two different fiber types were fabricated and crushed both statically and dynamically to examine the energy absorption characteristics. The fiber types, in the form of preimpregnated tow (towpreg) from Thiokol, were Akzo Fortafil 50k fiber and aerospace-grade T300 12k fiber. Using the towpreg, sixteen tubes were filament wound on aluminum mandrels. Three specimens were cut from each of these tubes for a total of forty-eight specimens. Twenty-four of these specimens were crushed statically in a load frame and twenty-four were crushed dynamically in a drop fixture. In order to characterize the tubes and specimens, a number of measurements were taken. These measurements included length, wall thickness, cross-sectional dimensions, volume, and mass. Two important energy absorption measures were examined: the specific energy absorption (SEA) and the ratio of the peak load to the average load. The geometry had a significant effect on the energy absorption but the stacking sequence did not. It was also found that the 50k material was less effective at absorbing energy than the 12k material, but the 50k still may be acceptable. / Master of Science

A new method for pre-impregnating nickel coated carbon fiber with a thermoplastic polymer to make towpreg, similar to a recently developed coating-line by João P. Nunes et al and a new electrically conductive thermoplastic are developed. A melted bath was used to help mitigate health concerns and waste for dispersion of nickel coated carbon fibers (NCF) in low density polyethylene (LDPE). This towpreg was then mixed with more LDPE or a mixture of LDPE and nickel nanostrands (NiNS) to a desired filler volume fraction to test the electrical conductivity of the composite. Some of these mixtures were then injection molded and tested again for conductivity as well as tensile and impact strength and compared to each other and the non-injection molded samples. It was found that mixing NiNS into the polymer in addition to NCF created a more conductive part than with NCF alone, in a couple orders of magnitude. Also, the shorter the NCF were, the greater the contribution of the NiNS to the electrical properties of the NCF filled material. The tensile strength was increased by adding the NCF and NiNS, while the impact strength (toughness) decreased.