3. RESULTS
From the static tensile tests we received the load vs. displacement curves and the mechanical properties for neat and nanocomposite cracked samples of crack lengths 2.0 mm and 3.0 mm at inclined angles ±30°, ±45°, ±60°. The data of 2.0 and 3.0 mm crack lengths were listed. For neat symmetrically double-edge-cracked samples the mechanical properties were presented in Table 1 for θ = 30°, θ = 45°, andθ = 60° and (a) for 2.0 mm, (b) for 3.0 mm crack length, respectively. Similarly, the mechanical properties for crack length 2.0 mm are expressed in (a) and crack length 3.0 mm in (b) for Tables 2-4. Next, for nanocomposite symmetrically double-edge-cracked samples, their mechanical properties were presented in Table 2 for θ = 30°,θ = 45°, and θ = 60°, respectively. As for neat anti-symmetrically double-edge-cracked samples the mechanical properties by tensile tests were listed in Table 3 for θ = 30°, θ = 45°, and θ = 60°, respectively. As for nanocomposite anti-symmetrically double-edge-cracked samples the mechanical properties were presented in Table 4 for θ = ±30°, θ = ±45°, and θ = ±60°, respectively.
From cyclic tests the P-N curves for neat symmetrically double-edge-cracked samples were shown in Figure 2(a) for crack length 2.0 mm and (b) for crack length 3.0 mm with θ = 30°, 45°, 60° together. The P-N curves for nanocomposite symmetrically double-edge-cracked samples were presented in Figure 3(a) for crack length 2.0 mm and (b) for crack length 3.0 mm with θ = 30°, 45°, 60°. Herein, the residual fatigue life is defined as the number of cycles due to applied loading that results in the broken sample with separated pieces. In the comparison of nano-powder SiO2improvement, for example, both the P-N curves for neat and nanocomposite anti-symmetrically double-edge-cracked samples were illustrated in Figure 4 for crack length 3.0 mm at θ = ±45°. The P-N curves for 2.0 mm and 3.0 mm crack lengths in nanocomposite anti-symmetrically double-edge-cracked samples were represented in Figure 5 for θ = ±45°.