Effect of notch on quasi-static and fatigue flexural performance of Twill E-Glass/Epoxy composite

An experimental study has been conducted to investigate the effect of notch on flexural (quasi-static and fatigue) performance of Twill E-Glass/Epoxy composite. Standard specimens and specimens with different types of notches configuration such as circular holes, transverse ellipse, longitudinal ellipse and slot geometry, have been prepared from plates and are considered for the study. Displacement-controlled bending fatigue tests with stress ratio R of 0.10 have been conducted on the selected specimens and damage in the composite has been continuously monitored through the decrement of bending moment during cycling. S–N curves are generated for the targeted composite material by cycling the coupons until failure and recording the number of cycles-to-failure. The results of un-notched specimens are then compared with those of coupons which have the selected notch geometries. Besides, the residual mechanical properties (flexural strength) of the material have been measured after loading the specimens to a preset number of cycles for coupon loaded at 30% and 45% of the Average Failure Load (AFL). The results are used to compare the rate of material degradation among the different type of notches. Finally, it is observed that different notched geometry behave differently for quasi-static and fatigue loading. For composite component subjected to quasi-static load, the failure is mainly governed by stress concentration (local failure) i.e. the notch size is not a significant factor. Whereas for composite component subjected to fatigue loading, the notch size becomes a dominant factor for failure and results to be more relevant than the stress concentration.