I’ve traveled quite a bit with scientific poster tubes and have never been questioned about carrying them on. If they stick out of your backpack or are strapped to the outside you likely won’t have any issues. I’ve also traveled many times with mountain bike helmets buckled to the outside of my carry on without any issues. Once you’re on the plane nobody will care if you take them out so they don’t get broken or ask a flight attendant if you can store them in the coat closet up front in first or business class (again airline dependent)