Static and fatigue characterizations of fiber glass/epoxy tubes exposed to internal pressure and/or bending moment

In this research, static and fatigue characteristics of fibrous materials is presented. The effects of fiber orientation, pressure ratio and mean stress on the fatigue characteristic of glass fiber/reinforced epoxy are investigated via testing tubular samples with different orientations of fiber [±45°]3s and [0°, 90°]3s. All samples were subjected to an internal pressure at several pressure ratios and/or a reversed bending moment. The test results indicated that, [0, 90°]3s samples had the highest bending strengths at various pressure ratios; when exposed to a minimum value of local shear stress which is zero. Pressure ratios effect is observed. It was obvious that any increase of pressure ratio had an adverse effect on samples fatigue strength for any orientation. Mean stress influence was discussed and it was stated that it had a detrimental influence on fatigue life samples with any orientation and at any pressure ratio. A new form of Goodman's equation for the present case of loading was presented and proved to be appropriate for demonstrating mean stress influence for present work.