Abstract

Liquid composite molding (LCM) is growing in importance alternative to traditional prepreg-autoclave methods for manufacture aerospace composites. The most significant roadblock to industry's implementation of LCM is the optimization of resin flow to ensure high quality parts. This study developed process optimization tools to foster the adaptation of LCM. The following dissertation characterized the permeability of reinforcement fabrics under various processing conditions, and investigated in-situ bubble flow with carbon fiber. The purpose of this research is to extend the understanding of LCM and push forward the state of the art via sub-studies captured in five chapters, or manuscripts. Research from these manuscripts is as follows. Chapter 3 sets the groundwork for LCM optimization by extending the current theory for assessing 3D permeability of reinforcement fabrics using an ellipsoidal point infusion experiment. The aim was to improve 3D permeability measurement accuracy for LCM processing models. This work is the first to compare solutions in the context of 75 experiments. Chapters 4 and 5 extend permeability analysis to curved and sheared geometries, typical to real-world aerostructures. Chapter 4 demonstrates a method for measurement of curvature effects on permeability with vacuum infusion. A correlation was shown between curvature (as evaluated over four radii) and effective permeability. Chapter 5 researches the shearing of reinforcement fabric (e.g. when reinforcements are draped over double curvature). The study shows that permeability actually increases for mid-range shear angles beyond the shear-locking angle, and develops a technique for obtaining the 3D permeability of sheared fabric.Chapter 6 investigates carbon fiber voids in situ. LCM optimization requires improved void monitoring for carbon fiber. It is challenging to monitor void flow in situ with carbon fiber reinforcements because of fiber opacity. The research builds upon a new automated fluorescent imaging method to monitor void flow in-situ. Results include high-resolution and high-contrast images and 230 data points for infusion velocity vs. void content data.Chapter 7 contributes to the growing interest in LCM processes for aerospace applications by providing a short cost summary of typical processes for manufacturing aerospace composite parts. Data shows that LCM is a financially wise alternative to automated fiber placement (prepreg-autoclave) manufacturing when a void content of 2-2.5% is acceptable. Work on LCM processes optimization indicates that these percentages will reduce in coming years.

Degree

PhD

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

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