Damage identification of composite material during stress rupture using acoustic emission technique

T300/5208 carbon epoxy laminated composite specimens, which were manufactured 19 years ago, and kept in a conventional normal environment, were tested for creep durability and Acoustic Emission behavior. It was found that the mechanical behavior as a whole, was retained, and degradation is minimal if any. The deep history under the load and the Acoustic Emission while under loading, was monitored continuously. Effects of different deformation modes, pure shear and in plane shear combined with interlaminar shear, were separated by choosing special kinds of specimens. It was found that the AE signature is different for the different modes of creep, but remains the same as 19 years ago. The strength and creep behavior are also about the same as 19 years ago. AE activity accelerates as creep rate increased and unconnected, AE accelerate towards the end of the creep life. The Pulse Height Analysis of the two shear stresses, are different in their slopes. Thus these characteristics can serve as sensors for creep rupture.