Design, analysis, and optimization of composite structures for aerospace applications

This thesis contains three papers that focus on composites that pertain to a variety of structures commonly found in the aerospace industry. The first paper presents an investigation of the stowage and deployment strength of a thin carbon fiber-reinforced polymer shell capable of being rolled and stowed in a tight rolled configuration. The intent of this structure is for use as a segment of a larger deployable reflective aperture. This study involved finite element analysis of several laminates, coupon-level and full-scale prototype testing, which provided a much needed insight and benchmark of composite shells used in this manner. The second paper outlines the principles and mathematical backgrounds of functionally graded materials (FGM) in engineering, as well as a review of representative recent studies of such materials. Additionally contained in this paper is an example that demonstrates the advantages FGM structures can provide. This example involves the optimization of a sandwich plate with in-surface graded facings to increase the bucking load and fundamental frequency without any weight penalty. This study was performed by interfacing the commercial finite element code Abaqus, with the Sandia National Laboratories developed optimization toolkit DAKOTA. The third paper focuses on energy harvesting using a flextensional bimorph. In this paper, a new concept of utilizing piezoelectric bimorph harvesters in combination with a flextensional strain amplifier is featured. To demonstrate the energy harvesting capabilities using this concept, a nonlinear finite element analysis of the bimorph harvester was conducted. As follows from the analysis, the new concept offers a possibility to harvest energy in a broad spectrum of driving frequencies, eliminating the major weakness of standard bimorphs related to a narrow useful frequency range. The papers contained in this thesis have displayed significant advancements to their respective application. The concepts and solutions considered in the papers offer significant possibilities for a development of advance aerospace structures --Abstract, page iv