Influence of notch geometry on bending fatigue behaviour of twill E-glass/epoxy composite

An experimental program is designed to study the effect of notch geometry on bending fatigue behavior of Twill E-glass/epoxy composite. Standard specimens and specimens with different type of notches geometry such as circular holes, transverse ellipse, longitudinal ellipse and rectangular slot, have been prepared from plates and are considered for the study. Displacement-controlled bending fatigue tests with R (stress ratio) of 0.10 were conducted and damage in the composite was continuously monitored through the decrement of bending moment during cycling. Besides, some set of specimens were subjected to 45% of the material ultimate flexural strength, tests were interrupted at 1 million cycles, residual properties were measured and compared with virgin specimen properties of both corresponding geometry and of other notched geometry. Finally, it is found that notched geometry specimens respond differently due to the variation of radius of curvature at the critical loading section of the notch, besides it is observed that smooth curvature transitions improve the fatigue strength.