Fatigue Properties of Carbon/PEEK [±30] Tubes under Multiaxial Cyclic Loading

Multiaxial fatigue behavior of carbon/PEEK tubes is discussed in this paper. Carbon/PEEK tubular specimens were fabricated from UD prepreg (APC-2/AS4 : ICI Fiberite Co., Ltd.) with a lamination of [±30] by a newly developed fabrication method. Repeated loadings of tension and compression combined with torsion were applied on the samples with an electro-hydraulic fatigue testing machine at a frequency of 10Hz. Multiaxial fatigue tests were actually performed under combined tension-compression-torsion cycles for the different ratio of axial stress and shear stress.

Methodology of fatigue strength estimation was discussed for the different biaxial stress ratio, σ/τ. Proposed method was confirmed to be useful for estimation of fatigue strength at the given lives for the various combinations of axial stress and shear stress, if the fatigue life data is available for the respective condition of cyclic axial loading and torsion. Discussion is also made on the fatigue failure mode of the tubular specimens under the different combinations of axial stress and shear stress.