Browsing by Author "Nel, Jan Heimriks"

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    Development and characterisation of a carbon fibre reinforced MAX phase composite material.
    (Stellenbosch : Stellenbosch University, 2017-12) Nel, Jan Heimriks; Blaine, Deborah; Sigalas, Iakovos; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: A carbon fibre reinforced MAX phase ceramic matrix composite (CMC) was produced in prepreg form and sintered using spark plasma sintering (SPS). MAX phase ceramics is a group of ternary ceramics exhibiting a combination of advantageous properties of both metals and ceramics. The CMC prepreg was designed with a carbon fibre weave acting as reinforcement and a MAX phase (Ti2AlC) acting as the matrix. Polymethyl methacrylate (PMMA) was used to coat the fibres and Ti2AlC powder combination to achieve a flexible and robust prepreg. Ti2AlC powder was prepared by attrition milling in a liquid medium. The particle size distribution was measured using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The mean particle size was reduced from 16 cm to 275 nm, allowing infiltration of the powder into a fibre weave. The effect of the attrition milling on the elemental composition of the powder was evaluated using energy dispersive spectroscopy (EDS) and powder X-ray diffraction (PXRD). Electrophoretic deposition (EPD), vacuum infiltration, and pressure infiltration were evaluated for ceramic infiltration into a carbon fibre weave. The ceramic infiltration was investigated by examining polished cross-sections using optical microscopy. Prepreg layers were combined and thermal debinding was performed at 400 °C to remove the PMMA coating. The CMC was sintered using SPS at 20 MPa and 1400 °C to create a 30 mm CMC disc. The sintered CMC had a density of 2.04 g/cm3 and open porosity of 16 %. The microstructure of the CMC was evaluated using optical microscopy, SEM, and X-ray computed tomography (CT). The discs were fractured using the ball on three balls (B3B) test method to determine the strength and mechanical response. EDS and SEM analysis was employed to evaluate diffusion between carbon fibres and Ti2AlC matrix. Aluminium diffused from the matrix into the fibres, resulting in the formation of Al4C3 in the carbon fibre and TiC in the matrix surrounding the fibre.