dynamic stiffness matrix for analysis of modal properties the damaged composite wing

In this paper, damage in composite wings is introduced, firstly, then using euler-bernoulli equations with including flexural and torsional coupling, governing equations on cantilevered composite wing is derived. by applying separation method damaged beam is converted to two interconnected intact beams and using boundary conditions and continues conditions in damage location, the dynamic stiffness matrix is composed and modal analysis of damaged wing is done. composite type is fiber-reinforced and damage type is edge crack with various locations and depths. also effects crack depths and locations on modal properties in various fiber angle are examined. results showed that existence a crack even with small depth in root of large span wing can reduce natural frequencies, seriously.