A unified approach to modeling delamination and matrix cracking in smart composite structures

The development of smart structures technology has coincided with the increased use of composite materials in structural design. Composite laminates have forms of damage that are not found in other materials, specifically delamination and transverse matrix cracking. An in-depth understanding of the effects of damage on smart composite structures is necessary for predicting not only the life of the structure, but also for modeling any method to be used for damage detection. The objective of this research was to develop a comprehensive model for accurately and efficiently modeling smart composite structures including the effects of composite damage.; First, a new, efficient method for modeling smart structures with piezoelectric devices was developed. The coupled model simultaneously solves for the mechanical and electrical response of the system using mechanical displacements and electrical displacements. The developed theory utilizes a refined higher order displacement field that accurately captures the transverse shear deformation in moderately thick laminates.; The model was then extended to include internal damage in the form of delamination and matrix cracking. When delamination is present, the sublaminates are modeled as individual plates and continuity is enforced at the interfaces. Matrix cracking was modeled as a reduction in laminate stiffness using parameters determined using finite element analysis of a representative crack.; Finally, the simultaneous optimization of both mechanical and electrical parameters in an adaptive structural system was studied. This study demonstrates how multidisciplinary optimization techniques, such as the Kreisselmeier-Steinhauser function, can be utilized to optimize both structural and electrical aspects of an adaptive structural system. Optimization of piezoelectric actuator placement and electrical circuitry was performed on passive electrical damping systems.; Results show that the developed model is capable of accurately modeling both the mechanical and electrical response of adaptive structures. These results show that traditional uncoupled piezoelectric modeling techniques do not take into account many electrical effects, resulting in significant errors in the sensor response predicted for transient loads. The developed model provides the ability to predict the effect of composite damage on the behavior of adaptive structures and to model potential methods to be used for damage detection.