Effect of load angle on the compressive failure of fiberglass/epoxy faced, honeycomb sandwich ...

225 Pages·2007·35.08 MB·English

In presenting the dissertation as' a partial fulfillment of
the requirements for an advanced-degree from the Georgia
Institute of Technology, I agree that the Library of the
Institute shall make it available for inspection and
circulation in accordance with its regulations governing
materials of this type. I agree that permission to copy
from, or to publish from, this dissertation may be granted
by the professor under whose direction it was written, or,
in his absence, by the Dean of the Graduate Division when
such copying or publication is solely for scholarly purposes
and does not involve potential financial gain.• It is under
stood that any copying from, or publication of, this dis
sertation which involves potential financial gain will not
be allowed without written permission.
• J
W
EFFECT OF LOAD ANGLE ON THE COMPRESSIVE FAILURE
FIBERGLASS/EPOXY FACED, HONEYCOMB SANDWICH STRUCT
A THESIS
Presented to
The Faculty of the Graduate Division
by
Robert Butler Lantz
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in the
School of Engineering Mechanics
Georgia Institute of Technology
September. 1968
EFFECT OF LOAD ANGLE ON THE COMPRESSIVE FAILURE OF
FIBERGLASS/EPOXY FACED, HONEYCOMB SANDWICH STRUCTURE
Approved:
7—^-^v
Date approved by Chairman: -^pf §_j_LlJV
ii
ACKNOlvLEDGNiENTS
I wish to express thanks to my thesis advisor, Dr. G. M. Rentzepis,
for his guidance, patience, and interest in the preparation of this
thesis, I also wish to thank the members of my thesis committee,
Dr, M. E. Ravi lie, Professor W. H. Horton, and Dr. D. J. McGill, for
their helpful suggestions.
The advice of my contemporaries is also gratefully acknowledged.
The numerous discussions with Mr. J. J. Grosko of Lockheed Georgia Com
pany and Mr. B. E. Kaminski, a fellow graduate student, concerning the
various technical aspects of this thesis were very helpful.
The gratis provisions of material, equipment, and services by
several major corporations proved invaluable for the completion of
this thesis. Special thanks are directed to Mr. R. B. Krieger,
Mr. J Shewmaker, and Mr. A. Allard of American Cyan amid Company,
4
Blooniingdale Department, for providing the laminates and sandwich panels.
The high quality workmanship displayed under the direction of Mr. Allard
was exemplary. Thanks are also directed to Mr. R. T. Tyler and BLH
Electronics, Inc., for providing strain gage rosettes; Mr. J. 0. Jones
and Technical Products, Inc., for providing use of their photcclastic
equipment; Mr. J. Belcher and Photolastic, Inc., for instrumenting the
photoelastic specimens; and Mr. J. W. Davis and the 3M Company, Indus
trial Tape Division}, for demonstrating the feasibility of the project.
The assistance provided by the Georgia Tech Foundation in
iii
initiating the project and Avco Aerostructmv. Division in completing
the project is greatly appreciated.
Finally, I wish to thank my wife Alice Cor her continual encourage
ment and unselfish sacrifice.
IV
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS ii
LIST OF TABLES vi
LIST OF ILLUSTRATIONS vii
SUMMARY ix
Chapter
I. INTRODUCTION . . . . .. 1
Orthotropic/Orthotropic Sandwich
Adhesive Prepregs
Failure Modes
Analysis Methods
Empirical Pitfalls
Purpose of Research, Scope
Tests Performed
II. IMSTRLff.ENTATION AND EQUIPMENT 11
Instron Description
Strain Measurements
Photoelastic (Photostress) Equipment
Special Test Fixtures
Calibration
Specimen Machining
III. EXPERIMENTAL PROCEDURE 29
Fiberglass Reinforced Plastic Material Property Tests
Sandwich Quality Control Tests
Sandwich Edgewise Compression Tests
IV. EXPERIMENTAL RESULTS AND EVALUATION 49
Facing Laminate Properties
Laminate Quality Control Tests
Sandwich Quality Control Properties
Edgewise Compression Tests
TABU: OF CONTENTS (Continued)
Page
V, CONCLUSIONS 91
VI. RETOMENDATIONS 94
Applications
Further Studies
APPENDICES
Appendix
1. QUALITY CONTROL DATA 96
t
Panel Process Data
Panel Flexural Shear Quality Control Test Data
2. RECORDED TEST DATA 154
Laminate Test Data (12 Ply 75DE181/BP919)
Sandwich Quality Control Test Data
Edgewise Compression Strength Test Data
Edgewise Compression Strain Gage Test Data
3. COMPUTER PROGRAMS 191
MIL-HDBK-17 Orthot.ropic Transformation Equations and
Program
FPL 1810A Face Wrinkling Program
Rosette Strain Gage Data reduction Program
Standard Deviation Strength Data Reduction Program
4. SANDWICH FLEXURE ANALYSES AND COMPARISONS 206
Isotropic Bending Analysis
Effective Stiffness Analysis
Comparisons
REFERENCE LIST 212
LIST OP TABLES
Table Page
1. Facing Laminate Tension and Compression Properties
(12 Ply, BP919/75DE181) 50
2. Facing Laminate Flexural Properties (12 Ply) . . . . . . .. 58
3. 0° Flexural Shear Sandwich Strength Results 62
4. Comparison of Ihree Ply Laminate Properties (Compression) as
Determined by Reduced 12 Ply Laminate Tests and Sandwich
Flexure Analysis . . . . .. 64
5. Comparison of Experimental and Calculated Stiffness of the
Sandwich Flexural Shear Tests . . . . . . . . . . . . . . .. 64
6. Face Wrinkling Stress Determined by Cell Size and
Load Angle 70
7. Shear Crimping Failure Strength Predictions . .. 72
8. Sandwich Edgewise Compression Strength Results . 86
9. Comparison of Three Ply Compression Properties from
Laminates and Sandwich Tests . . . . . . .. 87
vii
LIST OF ILLUSTRATIONS
Figure Page
1. Sandwich Conpression Failure Modes . . 5
2. Flexural Test Fixture 19,20
3. Laminate Conpression Test Fixtures . . . .. 22,23
4. Load Train Universal Joints . . . . .. . . .. 24
5. Flatwise Tension Adapter 25
6. Laminate Test Specimens 31
7. Laminate Tension Test . . . . . . . . . .. 32
8. Instron Tension Load-Strain Plot 33
9. Laminate Conpression Test . . . . . .. 35
10. Instron Compression Load-Strain Plot . . . . . . . . .. 36
11. Laminate Compression Failure . 37
12. Laminate Flexure Test 39
13. Sandwich Flatwise Tension Specimen 40
14. Sandwich Flatwise Tension Test . , 40
15. Sandwich Flexural Shear Test 42
16. Sandwich Edgewise Compression Test Specimen 44
17. Sandwich Edgewise Compression Test 46,47
18. Laminate Strengths (12 Ply) 52
19. Laminate Moduli (12 Ply). . . . . . .. 53
20. Laminate Strengths (3 Ply). 55
21. Laminate Moduli (3 Ply) . 55
viii
LIST OF ILLUSTRATIONS (Continued)
Figure Page
22. Sandwich Flatwise Strengths 60
23. Sandwich Flatwise Tension Failures . . . .. 60
24. Sandwich Edgewise Compression Failures of 90°
Oriented, 1/8 Cell Specimens 73
25. Sandwich Edgewise Conpression Stress Strain Response,
0° Oriented, 3/16 Cell 78
26. Sandwich Edgewise Compression Stress Strain Response,
30° Oriented, 3/16 Cell 79
27. Sandwich Edgewise Conpression Stress Strain Response,
45° Oriented, 3/16 Cell 80
28. Sandwich Edgewise Compression Stress Strain Response,
60° Oriented, 3/16 Cell 81
29. Sandwich Edgewise Conpression Stress Strain Response,
90° Oriented, 3/16 Cell 82
30. Sandwich Edgewise Compression Axial Stress Strain
Response - Comparison of Orientations, 3/16 Cell . . .. 83
31. Edgewise Compression Results (3/16 Cell Size) . . . . .. 88
32. Comparison of 3 Ply Strength Results . 89
33. Comparison of 3 Ply Modulus Results 90