Design, Manufacture and Analysis of a Carbon Fiber Epoxy Composite Acoustic Guitar Stephen M ...

193 Pages·2007·8.66 MB·English

Design, Manufacture and Analysis of a Carbon Fiber Epoxy Composite Acoustic Guitar

Stephen M. Probert

A thesis
submitted in partial fulfillment of the
requirements for the degree of

Master of Science in Mechanical Engineering

University of Washington
2007

Program Authorized to Offer Degree:
Mechanical Engineering

University of Washington
Graduate School

This is to certify that I have examined this copy of a master’s thesis by

Stephen M. Probert

and have found that it is complete and satisfactory in all respects,
and that any and all revisions required by the final
examining committee have been made.

Committee Members:

________________________________________________
Per Reinhall

________________________________________________
Vipin Kumar

________________________________________________
Vladimir Chaloupka

Date:______________________________________

In presenting this thesis in partial fulfillment of the requirements for a master’s degree at
the University of Washington, I agree that the Library shall make its copies freely
available for inspection. I further agree that extensive copying of this thesis is allowable
only for scholarly purposes, consistent with “fair use” as prescribed in the U.S. Copyright
Law. Any other reproduction for any purposes or by any means shall not be allowed
without my written permission.

Signature _____________________________

Date _________________________________

TABLE OF CONTENTS
Page
List of Figures...................................................................................................................v
List of Tables....................................................................................................................x
1 Introduction.................................................................................................................1
1.1 Origins of the Classical and Steel String Guitar...............................................1
1.2 The Anatomy of a Guitar..................................................................................4
1.3 Luthiers Dilemma: Tradition and Innovation...................................................7
1.4 Acoustic Research.............................................................................................9
1.4.1 Measurement Techniques.........................................................................9
1.4.2 Violin Research.......................................................................................12
1.4.3 Mode Labeling........................................................................................14
1.4.4 Guitar Research.......................................................................................15
1.4.5 Numerical Analysis of Guitars................................................................18
1.4.6 Psychoacoustic Analysis.........................................................................21
1.5 Carbon Fiber and Composites.........................................................................23
2 Design of the Guitars................................................................................................27
2.1 Cost Analysis and Sponsors............................................................................27
2.2 Analyzing a Wood Guitar...............................................................................28
2.3 Guitar Geometry—Developing a CAD model...............................................29
2.4 Preliminary Material Testing..........................................................................31
2.5 Preliminary Finite Element Analysis..............................................................34
2.5.1 Square Panel Test....................................................................................34
2.5.2 Deflection Out-of-Plane..........................................................................37
2.5.3 Deflection Due to String Tension...........................................................38
2.5.4 Modal Analysis.......................................................................................39
3 Manufacturing of the Guitars....................................................................................43
3.1 Molds..............................................................................................................43
3.2 Layups.............................................................................................................44
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3.3 Neck Prototype and Vacuum Fixtures............................................................51
3.3.1 First Neck Prototype...............................................................................51
3.3.2 Neck Vacuum Fixture.............................................................................53
3.4 Neck and Blocks.............................................................................................54
3.4.1 Neck Blank Preparation..........................................................................54
3.4.2 Milling the Neck Surface........................................................................58
3.4.3 Milling the Blocks...................................................................................62
3.5 Bonding of Back, Sides and Blocks................................................................65
3.5.1 Bonding the Back, Sides and Tail Block................................................65
3.5.2 Bonding the Neck Block.........................................................................68
3.6 Fretboard Shaping and Bonding, Headpiece Veneer and Heel Cap...............70
3.6.1 Fretboard Shaping and Bonding.............................................................70
3.6.2 Headpiece Veneer...................................................................................73
3.6.3 Heel Cap..................................................................................................73
3.7 Bridge Plate and Bonding the Top..................................................................73
3.8 Laser CNC Abalone Accents..........................................................................76
3.9 Epoxy Abalone and Fill Voids........................................................................78
3.10 Bridge Manufacture....................................................................................78
3.11 Neck Finishing............................................................................................80
3.12 Attaching the Neck.....................................................................................81
3.13 Lacquering, Sanding and Polishing............................................................83
3.14 Fretboard Inlays and Staining.....................................................................83
3.15 Fretting........................................................................................................84
3.16 Epoxy Bridge..............................................................................................87
3.17 Last Touches...............................................................................................88
3.17.1 Tuning Machines....................................................................................88
3.17.2 Nut and Saddle........................................................................................89
3.17.3 Pick Guard..............................................................................................91
3.17.4 Pickup, Preamp and Strap Pin.................................................................91
ii
3.17.5 Truss Rod Adjustment............................................................................92
3.18 Finished Guitar............................................................................................92
4 Comparison of Graphite and Wooden Guitars..........................................................94
4.1 Procedures.......................................................................................................94
4.1.1 Equipment...............................................................................................94
4.1.2 Boundary conditions...............................................................................95
4.1.3 Testing Procedure...................................................................................96
4.2 Results and Discussion...................................................................................98
5 Detailed FEA Model...............................................................................................105
5.1 Material Testing............................................................................................105
5.1.1 Procedures.............................................................................................105
5.1.2 Results and Discussion.........................................................................109
5.2 Finite Element Model Creation.....................................................................115
5.3 Finite Element Analysis Results and Discussion..........................................120
5.3.1 Results...................................................................................................120
5.3.2 Discussion.............................................................................................125
5.4 FEM Sensitivity Analysis.............................................................................127
5.4.1 Poisson’s Ratio Sensitivity...................................................................127
5.4.2 Elastic Moduli Sensitivity.....................................................................129
5.4.3 Shear Modulus Sensitivity....................................................................131
5.4.4 Foam Thickness Sensitivity..................................................................134
5.4.5 FEA Sensitivity Conclusions................................................................135
5.5 Conclusions...................................................................................................136
6 Psychoacoustical Study of Graphite and Wooden Guitars.....................................138
6.1 Procedures.....................................................................................................138
6.2 Results and Discussion.................................................................................140
7 Conclusions and Future Work................................................................................145
7.1 Conclusions...................................................................................................145
7.1.1 Comparison with a Wooden Guitar......................................................145
iii
7.1.2 Finite Element Analysis........................................................................145
7.1.3 Psychoacoustic Analysis.......................................................................146
7.2 Future Work..................................................................................................146
Works Cited..................................................................................................................149
Bibliography.................................................................................................................152
Appendix A: Guitar Machine Drawings.......................................................................156
Appendix B: Tooling Machine Drawings.....................................................................163
Appendix C: Additional Frequency Response Curves.................................................166
Appendix D: Vibration Testing Data............................................................................169
Appendix E: Guitar Rating Form..................................................................................171
Appendix F: Guitar Rating Raw Data...........................................................................172
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