Behavior of notched and unnotched [0/±30/±60/90]_s GFR/EPOXY composites under static and fatigue loads

摘要

The main objective of the present paper is to study the bending behavior of notched and unnotched angle-ply, [0/±30/±60/90]_s, glass fiber reinforced epoxy (GFRE) composites under static and fatigue loads. Static and fatigue bending properties have been determined for notched and unnotched angle-ply specimens. For this purpose different circular notch sizes (2, 4.5, 7, 9 mm) were drilled at the specimen center. Constant-deflection bending fatigue tests were performed at zero mean stress and 25 Hz. A 15% reduction of the initial applied moment was taken as a failure criterion. S-N diagrams for notched GFRE specimens have been constructed based on gross and net cross-section area. The results show that the ultimate bending strength of notched GFRE specimens decreased linearly with increasing notch diameter. Based on gross-section the fatigue life increases with decreasing notch size and the longer fatigue life was for the unnotched specimens. On the other hand, the S-N diagrams based on net-section indicate the insensitivity of angle-ply composites to the notch size. This is considered to be a peculiar phenomenon to composite materials. The results also show that the S-N diagrams have not any fatigue limit rigorous within 10~7 cycles.