| Carbon fibers with diameters ranging from 35 to 240 mum were deposited directly from a precursor gas by low-pressure LCVD. Laser chemical vapor deposition (LCVD) is a freeform processing method that locally heats an area exposed to a precursor gas. The gas decomposes by pyrolysis on the heated spot to leave a solid residue. In LCVD, the most significant experimental parameters are the incident laser power and precursor pressures.;The goal of this thesis is to present the local and bulk mechanical properties of these fibers. In this work, the mechanical properties are related to the fibre microstructure and clear mechanical properties dependence on experimental parameters is presented. The mechanical properties presented are the Young's modulus, the hardness, the tensile and fracture strengths as well as the bending resistance. To the author's knowledge, no measurement of the local mechanical properties of such fibers has been done so far. Hence, a radial analysis of the mechanical properties, achieved by nanoindentation, is presented. Also, only a limited investigation of the mechanical properties of high pressure LCVD carbon fibers has already been published. However, no information has been gathered on the bulk mechanical properties of LP-LCVD fibers and on possible mechanical properties deposition parameters dependencies. Hence, to complete the investigation of laser-grown carbon microfibers, a these-point bend test was devised and carried out with the use of a micromanipulator. (Abstract shortened by UMI.). |
