Selected issues of mechanics of ceramic matrix composites

Defect/damage tolerance and fracture of pressurized graphite/epoxy thin composite shells are evaluated via computational simulation. An integrated computer code that scales up constituent micromechanics level material properties to the structure level and accounts for all possible failure modes is used for the simulation of composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulation. Design implications with regard to defect and damage tolerance of thin-walled composite cylindrical shells are examined. A procedure is outlined regarding the use of this type of information for setting quality acceptance criteria, design allowables, damage tolerance, and retirement-for-cause criteria. Illustrative examples are presented for cylindrical and hemispherical shells. Results show that defects have a significant effect on the burst pressure.