Derstine, Mark S. | Search NASA

NASA NTRS1989

Experimental/analytical characterization of composite tubes under combined loading

The paper outlines the results of an investigation performed to characterize the response of P75/934 graphite/epoxy tubes with a stacking sequence of (15/0/+,-10/0/-15)s under pure torsion and combined axial/torsion loading. The experimentally observed nonlinear response and path-dependent failure are discussed in terms of material nonlinearites at the ply level and first ply failure loads with the help of an analytical model.

Derstine, Mark S.↗

NASA NTRS1988

Combined mechanical loading of composite tubes

An analytical/experimental investigation was performed to study the effect of material nonlinearities on the response of composite tubes subjected to combined axial and torsional loading. The effect of residual stresses on subsequent mechanical response was included in the investigation. Experiments were performed on P75/934 graphite-epoxy tubes with a stacking sequence of (15/0/ + or - 10/0/ -15), using pure torsion and combined axial/torsional loading. In the presence of residual stresses, the analytical model predicted a reduction in the initial shear modulus. Experimentally, coupling between axial loading and shear strain was observed in laminated tubes under combined loading. The phenomenon was predicted by the nonlinear analytical model. The experimentally observed linear limit of the global shear response was found to correspond to the analytically predicted first ply failure. Further, the failure of the tubes was found to be path dependent above a critical load level.

Derstine, Mark S.↗