Variable twist torsion tests on carbon fibre composite beams

A detailed experimental programme of work is presented which examines the c onstrained torsional response of carbon fibre composite beams for the canti levered configuration with torque applied at the free end. The behaviour of open-section beams and that of single-cell closed-section box beams is rep orted and discussed and the experimental findings are shown to corroborate simple engineering theoretical approaches. Tests have been carried out on z ed and angle-section beams and thus the effects of primary and secondary wa rping restraint respectively on the torsional response of open-section beam s are examined; The behaviour of zed-section beams is governed, in the main , by primary effects and that of angle-section beams is associated solely w ith secondary effects. The stress distributions along the beams and around the cross-sections are determined from the measured strains during test obt ained from surface bonded strain gauges and comparison of these with theory is shown to be in good agreement. The essential differences in response to constrained torsion between open and closed-section beams are detailed in the paper and the importance of experimental tests in the analysis of compo site structures is highlighted. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.