Characterisation of additive manufacturing materials for aerospace components

Fibre-reinforced composite materials have been gaining increasing popularity for Additive Manufacturing (AM) of aerospace components due to their significantly greater strength and stiffness to weight ratios, especially for Unmanned Aerial Systems (UAS) as structural stiffness is a crucial factor for effective control of multi-rotor configurations. The project attempts to characterise orthotropic linear elastic properties of AM Carbon Fibre Reinforced Thermoplastic (CFRP) material printed by Fused Deposition Modelling (FDM). The intent is to determine the orthotropic linear elastic properties of a Polyamide-12 matrix based short-fibre CFRP FDM material “Nylon-12 CF”, which can be used in Finite Element (FE) simulations to accurately represent any printed components of this material. These simulations can better guide the future design process of components printed with this material. The properties of FDM printed material are highly dependent on the process parameters such as extrusion width and extrusion raster orientation. They can be modelled using the orthotropic constitutive model. The nine elastic constants for this model, consisting of three Young’s moduli, three shear moduli and three Poisson’s ratios, were determined through mechanical tensile testing and non-destructive ultrasonic methods. Notable differences were observed in the behaviour and response of this material as compared to homogenous thermoplastic FDM material during these tests. Analysis of the tensile test fracture surfaces under a scanning electron microscope (SEM) revealed a greater degree of fusion between the individual extrusions and layers, and possible modes of failure of the specimens. Experimental validation of FE simulations of 3-Point and 4-Point bending tests, as well as distributed loading of a representative cantilevered aerofoil wing specimen were carried out, with the experimental results showing close correlation to the simulation results within the linear elastic range. This gives a reasonable degree of confidence in the obtained mechanical properties and method of simulation.Master of Science (Mechanical Engineering