Majid Safarabadi - Associate Professor, School of Mechanical Engineering, College of Engineering, University of Tehran
Mohammad Reza Shahrokhi - Bachelor Student, School of Mechanical Engineering, College of Engineering, University of Tehran

In unidirectional composite laminates, the magnitude of ultimate tensile strength decreases suddenly andsharply, when the on-axis part changes to off-axis specimen with a small angle. This angle is called “transient angle” inwhich the failure mode changes from fiber breakage to matrix cracking. In present study, this angle is determinedexperimentally. For this purpose, ۲۱ glass/epoxy specimens were made and tested with ۰, ۴, ۸, ۱۲ and۹۰ degrees fiberorientations. It was observed that in samples with ۴ degrees orientation, the ultimate tensile strength decreases ۱۶%,while in parts with ۸ degrees, a considerable drop is occurred equal to ۵۹% with respect to ۰degree specimens. There isnot any significant decrease in strength of ۱۲ degrees specimens in comparison with ۸ degrees pieces (only ۱۰%) and itis similar to the strength of ۹۰ degrees samples. So, the transient angle can be predicted equal to ۸ degrees.

transient angle, unidirectional composite, tensile test