TY - JOUR
T1 - Microstructure and damage evolution in short carbon fibre 3D-printed composites during tensile straining
AU - Almeida, José Humberto S.
AU - Miettinen, Arttu
AU - Léonard, Fabien
AU - Falzon, Brian G.
AU - Withers, Philip J.
PY - 2025
Y1 - 2025
N2 - Short-fibre thermoplastic composites offer a balance between cost, processability, and performance, as well as providing a use for recycled fibres making them attractive in various industrial applications. However, the fibres tend to be misaligned due to their low aspect ratio, which can impact mechanical performance. This work examines the as-manufactured microstructure of a chopped carbon fibre-reinforced nylon composite made by material extrusion additive manufacturing in terms of fibre misalignment, void content, shape and distribution before going on to determine its effect on damage evolution under tensile straining by in-situ time-lapse synchrotron computed tomography (CT). To this end, CT scans have been acquired at various stages throughout straining. A high degree of fibre alignment is observed with ≈86% within 14∘ of the extrusion axis, giving a Krenchel orientation factor of 0.75. The time-lapse CT image sequence reveals that because the mean fibre length (≈98μm.) is below the critical fibre length, fibre fracture does not take place during plastic straining. Instead, failure occurs during straining, from pre-existing voids and newly nucleated ones mainly located at fibre ends, their growth and coalescence. The experimental elastic modulus and strength are compared against the Cox-Krenchel and Kelly-Tyson analytical models that take into account fibre misalignment and length, which demonstrate that the fibre orientation is sufficient and future improvements in properties could be achieved by reducing the initial void content (≈2.3%) and increasing the length and volume fraction of the reinforcing fibres.
AB - Short-fibre thermoplastic composites offer a balance between cost, processability, and performance, as well as providing a use for recycled fibres making them attractive in various industrial applications. However, the fibres tend to be misaligned due to their low aspect ratio, which can impact mechanical performance. This work examines the as-manufactured microstructure of a chopped carbon fibre-reinforced nylon composite made by material extrusion additive manufacturing in terms of fibre misalignment, void content, shape and distribution before going on to determine its effect on damage evolution under tensile straining by in-situ time-lapse synchrotron computed tomography (CT). To this end, CT scans have been acquired at various stages throughout straining. A high degree of fibre alignment is observed with ≈86% within 14∘ of the extrusion axis, giving a Krenchel orientation factor of 0.75. The time-lapse CT image sequence reveals that because the mean fibre length (≈98μm.) is below the critical fibre length, fibre fracture does not take place during plastic straining. Instead, failure occurs during straining, from pre-existing voids and newly nucleated ones mainly located at fibre ends, their growth and coalescence. The experimental elastic modulus and strength are compared against the Cox-Krenchel and Kelly-Tyson analytical models that take into account fibre misalignment and length, which demonstrate that the fibre orientation is sufficient and future improvements in properties could be achieved by reducing the initial void content (≈2.3%) and increasing the length and volume fraction of the reinforcing fibres.
KW - 3D printing
KW - Failure mechanisms
KW - Fused filament fabrication
KW - In-situ testing
KW - X-ray computed tomography
UR - http://www.scopus.com/inward/record.url?scp=85212328867&partnerID=8YFLogxK
U2 - 10.1016/j.compositesb.2024.112073
DO - 10.1016/j.compositesb.2024.112073
M3 - Article
AN - SCOPUS:85212328867
SN - 1359-8368
VL - 292
JO - Composites Part B: Engineering
JF - Composites Part B: Engineering
M1 - 112073
ER -