Computational simulation of damage progression of composite thin shells subjected to mechanical loads

Defect-free and defected composite thin shells with ply orientation (90/0/ ± 75) made of graphite/epoxy are simulated for damage progression and fracture due to internal pressure and axial loading. The thin shells have a cylindrical geometry with one end fixed and the other free. The applied load consists of an internal pressure in conjunction with an axial load at the free end, the cure temperature was 177°C (350°F) and the operational temperature was 21°C (70°F). The residual stresses due to the processing are taken into account. Shells with defect and without defects were examined by using CODSTRAN an integrated computer code that couples composite mechanics, finite element and account for all possible failure modes inherent in composites. CODSTRAN traces damage initiation, growth, accumulation, damage propagation and the final fracture of the structure. The results show that damage initiation started with matrix failure while damage/fracture progression occurred due to additional matrix failure and fiber fracture. The burst pressure of the (90/0/ ± 75) defected shell was 0.092% of that of the free defect. Finally the results of the damage progression of the (90/0/ ± 75), defective composite shell was compared with the (90/0/ ± θ), where θ = 45 and 60, layup configurations. It was shown that the examined laminate (90/0/ ± 75) has the least damage tolerant of the two compared defective shells with the (90/0/ ± θ), θ = 45 and 60 laminates.