Development and characterization of ordered, highly oriented, composite laminates using supercritical carbon dioxide

This thesis describes the development and subsequent characterization of a series of oriented, highly ordered laminated composite materials. These laminated composite materials all possess order over varying length-scales from angstrom level molecular chain orientation to macro-scale order in woven fabrics. In each case, supercritical carbon dioxide (SC CO₂) is used as a unique reaction medium and processing aid allowing for the development of structures not previously attainable with standard techniques. The goal of this research is two-fold, the first goal involves the proof of concept, exhibiting the ability to attain novel composite structures using unique SC CO₂ chemistries and processes. The second goal of this research is aimed at developing a thorough understanding of how these unique structures and morphologies translate into an overall mechanical response for the material.; This work will be divided into three distinct but interrelated projects. The first project involves the development of a unique SC CO₂ assisted solvent welding technique. This technique is then applied towards the fabrication of a quasi-isotropic laminate comprised of a series of solvent-welded uniaxially-oriented linear low density polyethylene films (LLDPE). The geometry of this laminate is designed to exploit the improved strength and rigidity of uniaxially oriented LLDPE films while suppressing undesireable transverse properties.; The second project to be addressed in this project involves the development of fiber-reinforced composites with unique nano-scale morphologies. The long-range order in these composites has profound effects on both the individual fiber properties as well as the overall composite properties.; The final project of interest in this work involves the development of intercalated silicate nano-composites with high clay content. In order to achieve the desired morphologies it is necessary to create polymer/clay nano-composites with very high clay content, approaching 50% clay. This level of clay content is not currently possible with conventional techniques due to viscosity limitations. The focus of this project is to employ SC CO₂ as a reaction medium and a processing aid in the in-situ intercalation of silicate nano-composites with high clay content. Subsequent efforts in this area involve the orientation of these structures through the fabrication process itself or through post-reaction processing.