Correlation of Residual Strength with Acoustic Emission from Impact-Damaged Composite Structures under Constant Biaxial Load

Abstract

Small, filament-wound, Kevlar/epoxy, biaxial test specimens were sub jected to various levels of impact damage at the Oak Ridge Y-12 Plant.** The specimens were pressurized in a proof test cycle to 58% of their nominal, undamaged strength and then pressurized to failure. Acoustic emission data were gathered by multiple sensors dur ing a 10 minute hold at peak proof pressure. Post-test filtering of the data was performed to study composite behavior in the damaged region and other areas. The rate and total amount of AE produced depends on the duration of the static load and degree of damage. The concept of the event rate moment is introduced as a method of quantifying a struc ture's total AE behavior when under static load. Average event rate, total long duration events, and event rate moments provided various degrees of correlation between AE and residual strength.