Interlaminar fracture toughness GIC were measured using double cantilever beam (DCB) test for mode- I using area method, compliance method, compliance calibration method and modified beam theories. The results showed that epoxy reinforced with random glass fiber has higher GIC (2834 J/m2) than that of epoxy reinforced with woven roving glass fiber (548 J/m2). The results of different types of mid plane layers show that the Interlaminar fracture toughness GIC for [R7//M1/M1//R7]is (3018 J/m2) which is higher than that of [M7//R1/R1//M7] is(354 J/m2) . It was shown also that lay – up stacking sequences have an effect on the Interlaminar fracture toughness GIC . It was observed that GIC for [R/M//R1/R1//M/R]S is (1355 J/m2) which is higher than that [//M/R//]s is (260 J/m2) . Nano and micro SiO2 particles were used as a third phase filler for woven roving glass fiber composites with (2,4,6,8,10) wt % . It was found that higher GIC was observed for nanocomposites as compared with microcomposites . The results shows that Young modulus for nanocomposites was higher than microcomposites , but flexural strength for microcomposites was higher.