The point at which you'd need to be a little more concerned about it would be if you were to make something like a composite version of Cycra's probend handguards. They have a patent on something related to that bend, which is kind of a bullshit patent if you ask me, but that's another conversation. And again, no worries if you were only making something like composite parts to replace the plastic part of those handguards (like these). What it really comes down to is protectable intellectual property and there is none here (plastic handguard shields). Zero.