This is an experimental homebuilt aircraft, so the regulations on manufacture and replacement parts are much less stringent than commercially sold aircraft.
Also, the part it was replacing was a fiberglass part in an epoxy resin, with a glass transition temperature of 84°C. So the 105°C glass transition temperature of the replacement part should have been better than the original.
However, the original had an aluminum tube supporting the inlet, which provided extra structural support beyond fiberglass epoxy resin. And upon testing, the actual glass transition temperature of the 3D printed part was 52.8°C for one sample and 54.0°C for another, so much lower than expected.
Now, because the regulations are much less strict for experimental homebuilt aircraft, there may not be the traceability to figure out where in the chain the issue came up. Was it a bad batch of filament? Did the person making the part use the wrong kind of filament? Who should have tested the glass transition temperature of a coupon of the same material as the replacement part? Did the 3d printed material glass transition temperature change over time, possibly due to something like fuel or exhaust fumes?
The recommendation from this report is to disallow 3d printed replacements for this part, but it should be possible to do with the right material and proper testing and analysis (as well as leaving in the aluminum tube for additional support), as this is an air intake and it should be possible to find a 3d printed material that can withstand the kind of temperatures an air intake is subjected to, given that the original part is a fiberglass with epoxy resin.
Also, the part it was replacing was a fiberglass part in an epoxy resin, with a glass transition temperature of 84°C. So the 105°C glass transition temperature of the replacement part should have been better than the original.
However, the original had an aluminum tube supporting the inlet, which provided extra structural support beyond fiberglass epoxy resin. And upon testing, the actual glass transition temperature of the 3D printed part was 52.8°C for one sample and 54.0°C for another, so much lower than expected.
Now, because the regulations are much less strict for experimental homebuilt aircraft, there may not be the traceability to figure out where in the chain the issue came up. Was it a bad batch of filament? Did the person making the part use the wrong kind of filament? Who should have tested the glass transition temperature of a coupon of the same material as the replacement part? Did the 3d printed material glass transition temperature change over time, possibly due to something like fuel or exhaust fumes?
The recommendation from this report is to disallow 3d printed replacements for this part, but it should be possible to do with the right material and proper testing and analysis (as well as leaving in the aluminum tube for additional support), as this is an air intake and it should be possible to find a 3d printed material that can withstand the kind of temperatures an air intake is subjected to, given that the original part is a fiberglass with epoxy resin.