الفهرس 
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Abstract
A study of baxial fatigue of woven roving glass reinforced polyester subjected to in phase and out of phase cyclic bending and torsional moments is presented>To evaluate failure theories for this material tests conducted on two fiber orientations [0.90] and [45-45]tubes.More than 500 tubular specimens were fatigue tested with different ratios of the global flexural stress A to the global torsional shear stress B.These ratios were A/B=0.5,1,2 and many other values.The results showed that for 0.90 composites the S-N curves in pure bending and in pure torsion are sufficient to predict life contour for combined stress state and any theory of failure may be applied,while for [45,-45]tubes the value of the normal stress interaction component of a strength tensor H12 has to be obtained.If the ratio of A/B is less than 2 the value of H12 may be taken as presented by Tsai-Hahn theory.But if A/B>2 the value of H12 has to be obtained from {45,-45]pure bending S-N curve.The reason for this is that the failure mode is a combination of interfacial shear and matrix failure.In this case three tests are required to construct the life contour of the composites.These are pure bending fatigue test of{0,90]to get the flexural strength as a function of life N.pure torsion of [o.90]tubes to get the shear strength as a function of life N.Pure torsion of{0,90} tubes to get the shear strength as a function of life N and pure bending test of [45,-45]tubes to get the value of H12.The out of phase loading results showed that the lives of the specimens at high stress levels are less than that for the in phase loading with the same peak values A and B.