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The part was claimed to be ABS-CF. UK AAIB tested the part and found it to have a Tg of approximately 53C. The Tg of ABS is far higher, around 100C. I suspect t
by owenversteeg 11mo ago
The part was claimed to be ABS-CF. UK AAIB tested the part and found it to have a Tg of approximately 53C. The Tg of ABS is far higher, around 100C. I suspect that the part may have been accidentally printed with PLA-CF (which has a Tg of approximately 55C.)
The original part was fiberglass/epoxy with the epoxy having a Tg of 84C.
- brovonov 11mo agoPlastics under load have a lower Tg.
- hatsunearu 11mo agoIsn't Tg a poorly defined metric? It seems like thermoplastics will lose their strength as temperature goes up and there's no abrupt transition where there's a near step-change in behavior
- brovonov 11mo agoIt kind of is, a better metric is HDT (Heat Deflection Temperature), and it is based on curve usually load over temp.
- gpm 11mo agoAnd a datasheet for a (not necessarily the same) CF-ABS filament claims a HDT at 1.82 MPa of 93C: https://um-support-files.ultimaker.com/materials/1.75mm/tds/Method-ABS-CF/UltiMaker-Method-ABS-CF-TDS-v1.00.pdf https://um-support-files.ultimaker.com/materials/1.75mm/tds/... Something funny is going on with this material given the report is saying they measured a glass transition temperature of ~50C.
- ggreer 11mo agoI doubt there is any form of ABS filament with such a low glass transition temperature. As the original poster said, it was probably PLA. I find it odd that the report didn't name the manufacturer of the part, and that the part was not listed on the LAA modification form. There can't be many people selling such parts at airshows, so you'd think the investigators would have been able to find out who made it. Now I wonder if the previous owner (who installed the new fuel system) printed the part himself, then claimed he bought it overseas to avoid blame.
- CarVac 11mo agoTg changes? Or do you mean they deflect sooner under more load?
- deleted 11mo ago[deleted]
- nomel 11mo agoMaybe "load" includes the heat that comes from the changes forces from the vibrations? But even then, that would be additional heat sources, rather than a change in the temperature where it happens. Polycarbonate shows little change vs pressure [1]: [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6403934/ https://pmc.ncbi.nlm.nih.gov/articles/PMC6403934/
- Kirby64 11mo agoTg does not change with load. HDT does, kind of, but that’s already covered by the load being defined for the various conditions. HDT is always defined at a specific load so it also does not change with load (since load is fixed).
- boothby 11mo agoWhat's Tg?
- digitalPhonix 11mo agoGlass transition temperature I think
- emil-lp 11mo agoGlass transition temperature. https://en.wikipedia.org/wiki/Glass_transition https://en.wikipedia.org/wiki/Glass_transition
- deleted 11mo ago[deleted]
- owenversteeg 11mo agoGlass-liquid transition temperature, which is approximately where plastics and other materials change from hard and relatively brittle into flexible and rubbery. As the other comments here noted, it doesn’t exactly mean that the material is safe to use for a rigid part below that temperature, and the transition extends over a range in temperatures, but it does give you a rough idea about the behavior of a material at various temperatures.
- pawelduda 11mo agoSounds plausible but I guess it's something that they would've confirmed, had it been true Or it was ABS-CF but they forgot to dry the filament /s