The influence of stacking sequence on mode I interlaminar fracture toughness of glass fiber/epoxy composite panels

Delamination is a typical fracture mechanism in fiber reinforced composite laminates occurs due to low interlaminar strength. Some well-known sources of delamination under different loadings are free edges، cut out، low-velocity impact and fabrication defects. These damages may considerably reduce the global stiffnessand strength and then leads to a catastrophic structure failure. In this study، the influence of stacking sequence on mode I interlaminar fracture toughness of E-glass/epoxy laminated composites is experimentally investigated. On the other hand، delamination resistance and fiber bridging are investigated. Double cantilever beam (DCB) specimens with woven roving of glass fiber of stacking sequences; [0º/90º] 4s، [90º/0º] 4s and [±45º] 4s with an initial crack length are used. Load- displacement curve is obtained in DCB test and then interlaminar fracture toughness (GI) is estimated with R-curve. Results showed that interlaminar fracture toughness increased as the stacking sequence was changed from 0º to ±45º and ±45º to 90º and fiber bridging is more stable. Keywords: Mode I interlaminar fracture toughness، stacking sequence، delamination، composite panels.