Tensile properties of 3D-printed CNT-SGF reinforced PLA composites

Carbon nanotubes (CNTs) were coated on short glass fibres (SGFs) through a one-step flame synthesis technique. Then, these CNT coated SGF (CNT-SGF) reinforced polylactic acid (PLA) composite filaments were processed as a new fused deposition modelling (FDM) 3D printing feedstock. Tensile tests were conducted on FDM 3D-printed specimens with two raster angles (±45° and 0°/90°) each containing pure PLA filaments, SGF/PLA and CNT-SGF/PLA composite filaments separately. Compared to the pure 3D-printed PLA samples, experimental results showed that the 3D-printed specimens using SGFs (≥5 wt%) and CNT-SGFs (1–5 wt%) reinforced PLA filaments exhibited higher Young's modulus and tensile strength values due to the enhanced interface adhesion. Furthermore, the FDM printing raster angles (±45° and 0°/90°) did not noticeably affect the tensile properties of the samples made of the same material, which could be attributed to the complete fusion between adjacent rasters during printing. Scanning electron microscopy (SEM) images on the fracture surfaces of the tensile specimens indicated that the filler distribution within the printed samples was random. Theoretical calculations of the Young's modulus and computational fluid dynamics (CFD) simulation on SGF reinforced PLA samples further verified a random distribution of the fillers within the matrix due to the high printer nozzle diameter to SGF length ratio compared to the short SGF aspect ratio.