Mechanical Properties of Buckypaper Laminate Composites and Buckypaper Subjected to Microwave Irradiation

Author:  Paul A. Brayford
Institution:  Colorado School of Mines

Hydrogen has proven itself to be of particular interest as a clean renewable energy storage system. However, modern pressure tanks cannot handle the high pressures required to store the large quantities needed. Carbon nanotubes have already been shown as an effective mechanical reinforcement for composite materials. This research furthered this idea and studied if nanotube composites could be used as an outer reinforcement layer on pressure tanks. Laminate buckypaper composites and buckypaper subjected to microwave irradiation were tested. Single-wall carbon nanotubes were formed into buckypaper by vacuum filtration. Strips were cut from this paper and irradiated with microwaves in an effort to weld the nanotubes. Single and four ply laminate composites consisted of non-irradiated buckypaper strips and were layered with one of two epoxies. Tensile testing was conducted on samples press cut with a microtensile die conforming to ASTM D1708 standards. Samples were strained at 0.5 mm per minute until failure while recording the extension applied and resulting force. Laminate samples were also tested using field emission scanning electron microscopy to determine failure type and buckypaper epoxy impregnation. Microwave powers above 130 W were found to cause excessive damage to the buckypaper strips while 120 W formed only minimal damage. Samples microwaved at 120 W gave a 19 percent increase in average modulus of elasticity and a decrease of 31 percent in average ultimate tensile strength (UTS) in comparison to raw buckypaper. Both single and four ply laminates caused a decrease in both average modulus of elasticity and UTS, with the exception of four ply laminates with a 50 percent weight loading of epoxy where the UTS increased. Samples were determined to fail in a brittle manner and epoxy impregnation was found to be very low. With the low resulting average modulus of elasticities and UTSs, these buckypapers and composites were determined to not have the mechanical properties necessary for pressure tank reinforcement. Further research with larger sample sets is needed to determine this conclusively.

The Journal of Young Investigators is not affiliated with the US Department of Energy. This paper was written by a student intern with the Department of Energy and does not constitute a declarative position of either the Department of Energy or the Journal of Young Investigators.