The energy release rate for delamination in a laminated composite is supposed to be the material property being considered as independent of non-material property variables. However, Mode I fracture toughness(G_I) is found to vary with lamina arrangement, geometrical dimensions, and process-induced stresses.  In this investigation, the influence of lamina stacking arrangement on process-induced stresses and their effects on G_I of laminated composites are studied. Unidirectional (UD) ([0]₁₆) and cross-ply ([90₂/0₆]s, [90₄/0₄]s and [90₆/0₂]s) Glass/ epoxy (GE) composites with the delamination plane at 0◦//0◦ were prepared by manual layup method and post-cured at 120 °C for 4 hours. G_I of composite laminates were experimentally determined using a double cantilever beam(DCB) specimen as per ASTM D 5528. The slitting method was applied to determine the Process-induced stresses in GE laminates. The stacking sequence of laminas was found to have a noticeable effect on the state of residual stresses and G_I of GE laminates. Residual stresses do not have much influence on the G_I for delamination initiation, whereas G_I  for the crack propagation was found to increase with a gradual increase in compressive residual stresses in GE laminates.

Keywords: Residual stresses, Mode I interlaminar fracture toughness, slitting method

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