A research was conducted to evaluate the effect of voids which are generated during the fabrication of woven S2-glass/polyester composite laminates of the thickness of more than 20 mm. Four composite laminates having different percentages of void content up to 5 % were fabricated. The fabrication was specially proceeded so that the voids were equally distributed and fiber volume fraction was uniformly maintained; moreover, the shape and the size of voids were observed using microscopy. Attenuations of these laminates were measured by using 1 MHz and 4 MHz ultrasonic waves. Functional relationship between the void content percentage and the attenuation was extracted from the measurements. By measuring interlaminar shear strength and compressive strength of the laminates, the functional relationship between void content percentage and strength was also extracted. It was confirmed that the interlaminar shear strength and compressive strength are exponentially reduced while the void content percentage increased.
