| The objective of this dissertation research is to develop a computational "TOOL" to predict dynamic residual properties in laminated composites, i.e., characterizing the effects of fiber fracture, matrix cracking, fiber microbuckling and delamination on changes in the stiffnesses, natural frequencies, mode shapes and damping of laminated composites structures.; The approach utilized involves the development and extension of damage models which are then implemented in an existing finite element framework. These efforts include developing an internal state variable (ISV) damage model to represent the smooth transition in ply stiffness properties due to the initiation and propagation of intralaminar cracking of a laminate, developing a fiber microbuckling model at the ply level, and simulating damping characteristics and the variation with damage. Having a relationship between various damage modes and stiffness/damping properties allows for analyzing damage propagation under loads and significantly improves the determination of static/dynamic response characteristics and residual properties for laminated composite structures. Furthermore, it gives a better understanding of the nature and extent of damage as reflected by the residual properties.; The results of this work provide a general capability to model such damage modes at the macro-mechanics level, which would provide a much needed capability in the optimal design of composite structures. Furthermore, such modeling capability would be required in many "smart structure" applications. |
