Measurement, analysis and process planning for the layup of unidirectional fabrics

Manual layup has been a common method in the manufacture of composite structures for complex geometries. However, when production volumes and/or the quality requirements increase, there is an urgent need for solutions to automate the layup process. In addition, the trend in designing composite structures with increasingly larger dimensions and more complex geometries requires advanced process planning tools to optimize process parameters and guarantee the feasibility of the layup process. This dissertation presents a three-phased study on the development of automated and optimized process planning tools for the layup of unidirectional fabrics onto complex three-dimensional mold surfaces. The first phase of the study introduces the development of a laser scanning based measurement system, with the capability of measuring in-plane shear and out-of-plane deformations of unidirectional fabrics at the resolution of tow level. Based on this fabric deformation measurement approach, the second phase of study analyzes the effects of process parameters on the generation of different deformation modes and the transformation between them. The findings from the analyses were further explored to provide generalized solutions for improving the process of fabric layup in the third phase of the study, where two process planning tools are presented: pre-shearing planning and in-process manipulation planning. It has been verified by both simulation and experiments that these process planning tools are effective in increasing the drapability of the fabrics and in securing a feasible layup plan. Implementation approaches in layup process automation and composite structure design for manufacturability are also presented. The results of this dissertation can provide a path toward automated composite manufacturing that is both cost effective and reduces variability leading to flaws in large complex composites.