Date of Award
Herrington, Paul D.
The present study investigates microcracking and damage progression in IM7/977-2, IM7/5555, and IM7/5276-1 [0/90/90/0] laminates. For each material system, seven to eight small coupons were axially loaded in a tensile substage. At increments of around 50 MPa the surfaces of the specimens were inspected via optical microscopy so that a history of microcracking damage as a function of applied loading could be charted. In the IM7/977-2 laminates microcracks were found to initiate on average at around 1050MPa; microcracking initiation for the other two systems was around 850 to 900 MPa. Also, the IM7/977-2 system displayed a steeper increase in crack density as a function of applied loading than the other two systems. The IM7/5555 system was the only system that achieved a microcracking saturation density; the saturation density was found to be around 17 cracks per centimeter. While the IM7/977-2 and IM7/5276-1 systems typically broke into two pieces at failure, the IM7/5555 specimens shattered into pieces. In addition, delaminations were observed in a majority of the IM7/5555 specimens at loadings 250MPa under the failure loads.
Hottengada, Babruvahan, "Investigation of Microcracking and Damage Propagation in Cross-Ply Composite Laminates" (2006). University of New Orleans Theses and Dissertations. Paper 367.