Sheet Molding Compounds (SMC) present a promising alternative for sheet metal in automotive exterior body panel applications. They offer excellent specific mechanical properties, improved design freedom and a cost-efficient manufacturing process. However, the paintability of SMCs is challenging and this issue has kept the material from a more widespread application, in spite all inherent advantages.
This work investigates the underlying reasons of paint defect occurrence and proposes novel solutions to improve upon state-of-the-art technology. Through the modification of conventional SMC an improved surface compound is proposed. This can be combined with a novel manufacturing process, denoted Co-Compression-Molding, which enables the molding of two individual compounds in a single step. The work offers insight into appropriate molding parameter selection to ensure a flawless compression molding process. Additional processing steps are proposed to further improve manufacturing, such as thermography for the early detection of sub-surface voids, and post-processing via electron beam curing.:1 Introduction
1.1 Motivation and Objectives
1.2 Solution Approach
2 State of the Art
2.1 Automotive Production
2.1.1 Paint Processes
2.1.2 Quality Assessment Techniques
2.2 Sheet Molding Compounds
2.2.1 Manufacturing and Composition
2.2.2 Mechanical Properties
2.2.3 Conventional Methods of Surface Improvement
2.2.4 Recycling Methods
2.3 Compression Molding
2.3.1 Mold Flow of Sheet Molding Compounds
2.3.2 Compound Rheology
2.3.3 Inherent Porosity
2.3.4 Co-Molding Process
2.3.5 Alternative Approaches and Auxiliary Processes
3 Reduced Fiber Weight Fraction Compounds
3.1 Porosity as the Source of Defects
3.2 Compounding and Compression Molding
3.3 Compound Characterization
3.3.1 Fiber Network Permeability
3.3.2 Rheology and Flowability
3.3.3 Physical Properties
3.3.4 Pore Content and Porosity Elimination
3.4 Effect on Paintability
4 Co-Compression Molding
4.1 Hybrid Material Flow
4.2 Materials
4.3 Molding Trials and Testing
4.3.1 Flat Plaque Testing
5 Auxiliary Processes
5.1 Thermography
5.1.1 Materials
5.1.2 Experiments
5.2 Electron Beam Curing
5.2.1 Residual Reactivity
5.2.2 Irradiation and Post-Curing
6 Full-Scale Trials
6.1 Class-A Panel
6.2 Semi-Structural Component
6.3 Technology Demonstrator
6.3.1 Cost Comparison
6.4 Application Guidance
6.4.1 Reduced Fiber Fraction Compounds
6.4.2 Co-Compression Molding
6.4.3 Application of Auxiliary Processes
7 Summary
Bibliography
Appendix
A Evolution of Vehicle Curb Weight
B Porosity Structure of Normal Density Compound
C Surface Veil Distortion During Compression Molding
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:79734 |
| Date | 24 June 2022 |
| Creators | Kardos, Marton |
| Contributors | Modler, Niels, Vaidya,, Uday, Täger, Olaf, Technische Universität Dresden, Volkswagen AG |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | urn:nbn:de:bsz:14-qucosa2-715610, qucosa:71561 |
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