Elhabak, A.M. and Adly, M.
Mech. Design & Prod. Dept., Faculty of Engineering, Cairo University
The knee in the acoustic emission cumulative counts curve has been proposed as a possible
solution to the absence of a characteristic yielding point in the stress-strain curve of composite
materials. Yield strength could eventually be adopted in the engineering design as an
alternative to the currently used maximum strength. A series of tensile type experiments have
been carried out for investigating the possibility of assessing this point for glass
fiber/polyester resin composites. Coupons with two stacking number of layers have been
examined under tensile experimental conditions. The derived value of the woven polyester
composites for their yield strength fall within reasonable range of 35-40% with respect to
their maximum strength.