ABSTRACT
The strength of two and three plies FRP composite was evaluated using ring burst test developed by the authors [1, 2]. The fracture behavior during the tests of damaged FRP was characterized by an 8mm video camera, a high magnification video scope, strain measurements and AE analysis. Ring specimens were fabricated by a filament winding (FW) machine. In this study, following two types of simulated damages were introduced artificially into the FW-FRP specimens. The notches were introduced by cutting wheel mechanically and the pre-existing interlaminar delaminations were introduced by inserting a teflon sheet between the outermost and the inner FRP layers during fabrication. The strength of unnotched specimen with or without pre-existing interlaminar delamination was nearly equal to the rule of mixture (ROM) value. On the other hand, the strength of notched specimen was larger than the predicted pressure based on the premise that the notched outermost ply could not sustain the load. However, as the teflon sheet was longer, the strength was decreased gradually. The fracture behavior of FW-FRP composite, especially propagation of interlaminar delamination, was characterized by the AE analysis and observation using the above three techniques. It was demonstrated that AE technique was powerful for the detection of pre-existing interlaminar delamination and the monitoring of delamination propagation in FW-FRP composites. Consequently, the fracture behavior of FW-FRP composites with damages was understood.
