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A Novel Composite Tube Design with Bend-Twist Coupling



A novel design of a composite circular tube possessing bend-twist coupling at the structural level is presented. When subjected to a bending moment the tube undergoes twisting in addition to bending. Conversely a torque results in bending in addition to rotation. This coupling causes the shear center of the cross section to be away from the center of the tube. An analytical model is proposed and closed-form equations for shear center distance are derived for both straight and tapered composite tubes. The results are verified by performing finite element analysis. Special tubes were fabricated and tested to measure the shear center distance. The agreement in results is excellent. It is found that the location of the shear center is independent of the shaft radius but proportional to the length of the tube.

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