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After recently publishing a few videos covering research into the poor adhesion between chopped carbon fiber (CCF) and the thermoplastic filaments as used with FDM 3D printing, some of the feedback received by [I built a thing] included the idea that the missing step to make CCF additives work was post-print annealing. Naturally this claim had to be investigated, both through the resulting physical characteristics as well as on a microscopic level in the same scanning electron microscope (SEM) as before.
Post-annealing SEM scan, showing clear voids. (Credit: I built a thing, Youtube)
Theories as to why annealing the parts would help here seem to focus on increased bonding and filling of voids in the printed CCF-infused material, while there are the typical worries with annealing such as parts warping and shrinking to also take into account as potential downsides of this treatment.
For the sample materials PETG and PETG-CF, as well as PLA and PLA-CF filaments are used, with each filament type featuring an annealed and not annealed version. These were then tested for tensile strength, stiffness and failure type, as well as dimensional accuracy and warping, before being examined under the SEM. A total of 160 samples were used, with 20 samples per material and annealing state.
