What materials should you consider for functional 3D printed prototypes?

I totally agree with the description above for PLA. Nevertheless, I will like to add that due to it's less expensive makes it more suitable for beginners and anybody who wants to try out any project even if it will require a more dedicated material like fiber mix. Considering PLA for functional prototype will be that such will not require exposure to high temperature.

PLA is one of the most affordable, easy to use, easily available 3D printing material in the market. Available in multiple colours PLA is best suited for hobbyists, general prototyping and basic form, fit applications. It’s also the most economical material to work with as it prints at lower temperatures and is less prone to warpage and print failures. PLA in the form of Tough PLA is an easy to print material which has strength similar to ABS. It’s neither heat nor chemical resistant but has better tensile strength.

ABS is the most common material that you will come across in your day to day life. Hence if you use ABS in your end use part it’s worth testing out your prototypes or functional tests in this material before you proceed further. ABS is also very tricky to print as it can warp easily. Having a heat controlled chamber always helps. ABS has better strength and heat resistance than PLA and is the go to material for functional applications.

I will say PETG is one material type that will mostly fit into clients requirements due to it's flexibility to act as PLA or PETG.

PETG is also an easy to print functional material which has similar or slightly better properties than ABS. You can choose PETG over ABS if you require certain bit of chemical resistance, better tensile properties along with ease of printing.

TPU is an elastomer material and is available in various shore hardness. Choose a direct drive FFF printer if you want to print more flexible filaments of TPU. TPU is also available in powder form for SLS technology. TPU parts mimic rubber like properties which can be used in bellows, grips, vibration dampners etc. TPU can also be used to print wearables and insoles.

Nylon is a functional material which can be used to make snap fits, chemical resistant and strong parts that withstand wear and tear. Nylon is hygroscopic in nature and can be a difficult material to print. Nylon is best used with SLS technology for making functional, lightweight, end use parts. Nylon can also be combined with Carbon fiber or glass fillers to achieve better strength and heat resistance.

Nylon FDM material is one FDM material that will want to try your patience but with experience it will always proof to be the best material for functional prototype that requires tough strength.