A new flexural-tensegrity bow

The bow is a simple machine now representing a paradigmatic example for demonstrating the applicability of the structural concept of flexural tensegrity, as chains of segments in unilateral contact coupled by unbonded prestressing tendons. The nonlinear and nonlocal constitutive laws for bending are dictated by the tendon prestress and, explicitly, by the shape of the contact surfaces between segments. Optimization requires functionally graded elastic properties fulfilling different objective functions, in terms of energetic efficiency, arrow exit speed, shooting accuracy, archer's comfort. An innovative non-recurve composite bow, called FlexTen bow, is theoretically analyzed, prototyped and tested, under static and dynamic conditions. Two different designs are considered, identical except for the shape of the contact surfaces between segments, so that the lever arm of the internal couple is either a linear or a sub-linear function of relative rotation. The FlexTen bow with sub-linear behavior outperforms classical bows, but the advantages, yet to be fully appreciated, also consist in the modular construction and the possibility of packaging.