TITLE:
Recipe Development and Mechanical Characterization of Carbon Fibre Reinforced Recycled Polypropylene 3D Printing Filament
AUTHORS:
Mwambe Polline, James M. Mutua, Thomas Ochuku Mbuya, Kyekyere Ernest
KEYWORDS:
Fused Filament Fabrication, Fused Deposition Modeling, 3D Printing, Carbon Fibre Reinforced Polymers, Polypropylene, Plastic Recycling
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.11 No.3,
July
30,
2021
ABSTRACT: Recycled polypropylene filaments for fused filament
fabrication were investigated with and without 14 wt% short fibre carbon reinforcements. The microstructure
and mechanical properties of the filaments and 3D printed specimens were
characterized using scanning electron microscopy and standard tensile testing.
It was observed that recycled polypropylene filaments with 14 wt% short carbon fibre reinforcement contained pores that were
dispersed throughout the microstructure of the filament. A two-stage filament
extrusion process was observed to improve the spatial distribution of carbon fibre reinforcement but did not reduce the
pores. Recycled polypropylene filaments without reinforcement extruded at high
screw speeds above 20 rpm contained a centreline cavity but no spatially
distributed pores. However, this cavity is eliminated when extrusion is carried
out at screw speeds below 20 rpm. For 3D printed specimens, interlayer cavities
were observed larger for specimens printed from 14 wt% carbon fibre reinforced recycled polypropylene than
those printed from unreinforced filaments. The values of tensile strength for
the filaments were 21.82 MPa and 24.22 MPa, which reduced to 19.72 MPa and 22.70 MPa, respectively, for 3D printed samples using the filaments. Likewise,
the young’s modulus of the filaments was 1208.6 MPa and 1412.7 MPa, which reduced to 961.5 MPa and 1352.3 MPa, respectively, for the
3D printed samples. The percentage elongation at failure for the recycled
polypropylene filament was 9.83% but reduced to 3.84% for the samples printed
with 14 wt% carbon fiber reinforced polypropylene filaments whose elongation to
failure was 6.58%. The SEM observations on the fractured tensile test samples
showed interlayer gaps between the printed and the adjacent raster layers.
These gaps accounted for the reduction in the mechanical properties of the
printed parts.