Date of Award

2017

Document Type

Open Access Thesis

Department

Mechanical Engineering

Sub-Department

College of Engineering and Computing

First Advisor

Ramy Harik

Second Advisor

Zafer Gürdal

Abstract

Automated manufacturing of fiber reinforced composite structures via numerically controlled hardware yields parts with increased accuracy and repeatability as compared to hand-layup parts. Automated fiber placement (AFP) is one such process in which structures or parts are built by adding bands of prescribed number of tows or slit-tape with prescribed width using robotic machine heads over 3D surfaces following prescribed paths. Despite the improved accuracy, different types of defects or manufacturing features arise during fabrication. These defects can be due to geometrical features, materials, and process planning parameters and are detected in the form of wrinkling, tow twist, tow folding, overlap, gaps and several others.

This thesis presents a thorough investigation of wrinkling within a path on a general surface for a composite tow constructed using the AFP process. Governing equations and assumptions for the presented model are derived based on geometric considerations only, neglecting the elastic properties of the material, and formulated for an arbitrary curve on a general three-dimensional surface. A simple form of the wrinkled shape is assumed and applied to the inner edge of the tow path. A numerical solution is implemented within Mathematica to visualize the curved paths and to indicate potential regions for wrinkling on the surface. Several examples are presented to demonstrate the model, including constant angle paths on a double-curved surface and curved paths on a flat surface. The obtained deformed patterns are compared with actual data from digital image correlation (DIC) of several towpaths.

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