Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Tutunea-Fatan, Remus

Abstract

Thermoplastic composite parts are manufactured using compression molding for the purposes of assembly in a car seat sub-assembly. Concerns about the dimensional accuracy of the parts prompted an investigation into the part warpage. The warpage of the parts needs to be evaluated for the purposes of determining processing conditions which are linked to part warpage, in order to reduce part warpage.

Laser line probes (LLP) are becoming a more attractive tool for the purposes of part inspection. LLPs quickly acquire point cloud data from complex surfaces and are a non-contact method of measurement; these qualities make LLPs the best tool for the inspection of warped composite parts. Currently there are no guidelines for inspecting this class of parts which require special scanning conditions (no rigid fixtures). There exists no evaluation of the repeatability or accuracy of LLP scans under these specific scanning conditions. To address this knowledge gap, research was conducted comparing several methods of scanning to outline a scanning procedure which would provide reliable results.

Similarly there are no guidelines for warpage measurement in general. The method of measuring warpage is typically informed by part geometry and warpage behavior, and thus can be different for each case. To address this issue several warpage metrics are proposed and applied to discover the effectiveness of each method. Finally the investigation of processing parameters can be accomplished. In this thesis several experiments are conducted to understand the impacts of mold temperature, charge placement, material, and geometry on the final part warpage.

Summary for Lay Audience

Composite parts are made from a plastic matrix which is embedded with fibers (common fibers include glass and carbon fibers). Composites are useful materials for the automotive industry because they are both light and strong. Compression molding is a method of mass production which can be used to produce composite parts. Unfortunately parts made of composite materials which are manufactured using compression molding do not come out perfectly. The geometry is slightly different than what it was intended to be, this is commonly known as warpage. A method of quantifying warpage is needed to investigate potential causes of warpage.

Laser line probes (LLP) are an advanced tool which is used for gathering measurements on objects. This is achieved by using lasers to scan the object and replicate the object on a computer. Using the replicate of the object on the computer measurements can be obtained from the object. The use of LLPs to evaluate the warpage on composite parts is not well documented in literature. There is no assessment reporting the expected accuracy of the measurements obtained using this tool on a part made of composite materials. To address this gap in knowledge a study was conducted which compared many methods of applying the LLP to scan a composite part. The aim of the study was to outline the most accurate way of using an LLP to scan a composite part and what the accuracy of this method is.

Collecting the warpage measurement is the next step required to evaluate the composite parts. There is no set standard for collecting warpage measurements. Methods of measuring warpage used in previous work are very simple and are not necessarily the best methods of measuring warpage for the specific work carried out in this thesis. To deal with this problem several methods of measuring warpage are proposed and investigated. Finally a study is conducted to find out how some manufacturing conditions impact the warpage of the composite parts.

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