Defect detection in 3D printed carbon fibre composites using X-ray Computed Tomography

Abstract

X-ray Computed Tomography (X-ray CT) has become a vital tool for product quality inspection. The X-ray CT analysis of 3D printed composites, with a layer-by-layer structure of carbon fibre/polyamide and polyamide plies, demonstrates how the void content increases with an increasing number of consecutive carbon fibre layers. Not only the void content, but also the pore network complexity increases, as more pore types are introduced into the sample. The PolyAmide (PA) matrix has an average void content of 6%, consisting of interbead channels with strong anisotropy. Alternating a carbon fibre layer with two polyamide layers slightly increases porosity (6.8% on average), as both inter- and intrabundle porosities are now present. It was found that the premature cutting of the carbon fibre bundle results in a large void at the end of the print path, while the start of the path is also associated with voids and an interruption of the PA wall layers. Full carbon fibre layering sections introduce additional large voids (average porosity of 9.7%), as the carbon fibre bundle cannot fully move into the corners of the polyamide wall layers. The tested samples exhibit a delamination failure mode in the performed indentation test. The 100°PA2CF lay-up exhibits the best performance, yielding the highest loading and actuation potential. The presence of a PA layer between CF layers is beneficial for the mechanical performance of the printed carbon fibre composite. While reinforcements are introduced to enhance the mechanical strength and elasticity of thermoplastics, or to invoke an actuation mechanism, the final material properties strongly depend on the used fill pattern, the location of the start and end points of the print pattern, the turn radius, the lay-up, and more specifically the number of consecutive reinforcement layers.