Hybrid Carbon Nanotube-Composite Architectures

Hybrid composite architectures employing traditional advanced composites and carbon nanotubes (CNTs) offer significant potential mechanical and multifunctional performance benefits. Dense patterns of well-aligned carbon nanotubes (CNTs) were grown on silicon wafers using a thermal chemical vapor deposition (CVD) process [1]. Wetting of CNTs and retention of mechanical properties of the fibers after the CVD process are considered fundamental issues related to realizing novel hybrid composite architectures. Wetting of CNT forests by several commercial polymers (including a highly-viscous epoxy, as shown in Figure 1) has been demonstrated at rates conducive to creating a fully-dispersed CNT/matrix region around the fibers in hybrid architectures [2]. A new microfabrication method [3] was developed to create wellaligned, regularly contracted pillars. The basic mechanical properties (elastic modulus, strength) of the polymer and the CNT/polymer nanocomposite were obtained by means of a nanoindenter to apply a compression test to the vertically aligned circular composite pillars [3]. The elastic modulus was obtained using the Oliver-Pharr theory adapted to the flat punch used in the experiments. These intermediate architectures of aligned CNTs in a polymer matrix are being employed to create more sophisticated architectures utilizing advanced fibers and prepregs of traditional advanced composites [4-5]. The dense, aligned, high-quality forests of CNTs grown at high rates (~50 microns per minute) suggest that the process is scalable for incorporation into traditional composites. Single-fiber tension tests [6] indicate no mechanical degradation for fibers undergoing the CNT growth process, as shown in Figure 2c). Results indicate that hybrid CNT/composite architectures are feasible; future work focuses on mechanical and multifunctional property characterization of other hybrid architectures and scaling to a continuous CNT growth process.