What's the strongest filament so far?

You can't use matweb data. That's just an average and is not at all representative of printed parts. Even considering standard stress/strain data if you know it for the specific grade of material used in the filament might not mean much since there is a lot of variability in layer adhesion.

I've tested a lot of different materials (browse through my blog to see some).

I think Taulman 645 produces the strongest printed part right now. Nylon printed parts approach the strength of injection molded (not necessarily injection molded nylon, but generally what you would expect from an injection molded part).

The PETs (PET+, colorfabb XT, Taulman t-glase) also give you great strength for a printed part.

HIPS is the weakest.

ABS is also fairly weak for a printed material unless you are really using a lot of layers. The strength to weight ratio is not what you might think when you consider ABS as a material used in car molding parts and legos. It does have nice ductility, flexibility, and decent impact strength relative to other choices. I think that the popularity of ABS as a printing filament will have gone way down by the end of the year.

The carbon fiber filament is NOT intended to be stronger than other materials. It is intended to be stiffer. It really is noticeably stiffer than any other material I've printed with. So stiff that I'm not positive the 3mm will print on bowden machines without snapping.

PLA is actually very strong, but since it is so brittle, it breaks relatively easily and has poor impact strength. If you make a piece and load it slowly, it will take a lot of force to deflect it, but once it does, it snaps abruptly and violently. Likewise, if you drop it too hard, it is more likely to break than other materials.

PLA/PHA is a blend of the two materials that gets most of the strength of PLA with some of the flexibility and impact strength of ABS. I'm a huge fan of this material.

 

Thanks.

Nope, PET is a thermoplastic. same as ABS, PLA, Nylon or anything else we're putting through our printers.

Epoxies are thermoset polymers. You can't melt and resolidify a thermoset.

Everything you put through filament extruding printer like the robo is going to be either a thermoplastic or something mixed into a thermoplastic (like the wood or carbon fiber filaments). Thermoplastics are polymers that can be melted and then resolidify. All of your recyclable plastics are thermoplastics. As an FYI, everytime you melt and resolidify a thermoplastic, you are damaging the polymer chains. So, recycled plastic will not have quite the same properties as a 'virgin' plastic. Every time you melt it again, you degrade those properties more. That's one part of the explanation around why our 3D printed materials are not as strong as anything you see quoted on matweb. They've already been melt processed at least twice before we extrude them. Once for color compounding (at least part of the batch) and then again for extrusion into filament form.