Characterization of Energy Absorbing Materials for Blunt Trauma Reduction

79 Pages·2015·3.1 MB·English

Florida State University Libraries
Electronic Theses, Treatises and Dissertations The Graduate School
2008
Characterization of Energy Absorbing
Materials for Blunt Trauma Reduction
María Isabel Roquer Schober
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FLORIDA STATE UNIVERSITY

FAMU-FSU COLLEGE OF ENGINEERING

CHARACTERIZATION OF ENERGY ABSORBING MATERIALS FOR
BLUNT TRAUMA REDUCTION

By

MARÍA ISABEL ROQUER SCHOBER

A Thesis submitted to the
Department of Industrial Engineering
in partial fulfillment of the
requirements for the degree of
Master of Science

Degree Awarded:
Spring Semester, 2008
The members of the Committee approve the Thesis of María Isabel Roquer Schober
defended on November 21, 2007(cid:1)

Okenwa O. I. Okoli
Professor Directing Thesis(cid:2)

Samuel Awoniyi
Committee Member

James Simpson
Committee Member

Ben Wang
Committee Member

Approved:

Chuck Zhang, Chair, Department of Industrial and Manufacturing Engineering(cid:2)

Ching-Jen Chen, Dean, FAMU-FSU College of Engineering(cid:2)

The Office of Graduate Studies has verified and approved the above named committee
members.
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LIST OF TABLES ............................................................................................. iii
LIST OF FIGURES ............................................................................................ iv
ACKNOWLEDGEMENTS ............................................................................... vi
ABSTRACT ..................................................................................................... vii
CHAPTER 1 INTRODUCTION ........................................................................ 1
1.1 Introduction .......................................................................................... 1
1.2 Problem Statement ............................................................................... 2
1.3 Research Objectives ............................................................................. 3
CHAPTER 2 LITERATURE SURVEY ............................................................. 4
2.1 Introduction .......................................................................................... 4
2.2 Material properties of polymers ........................................................... 8
2.3 Mechanics of foams ............................................................................. 18
CHAPTER 3 EXPERIMENTAL SETUP ........................................................... 31
3.1 Material Characterization ..................................................................... 31
3.2 Mechanical Properties ......................................................................... 31
3.3 Impact Resistance Test ......................................................................... 33
CHAPTER 4 EXPERIMENTAL RESULTS ...................................................... 42
4.1 Material Characterization ..................................................................... 42
4.2 Mechanical Properties Results ............................................................. 44
4.3 Impact Tests Results............................................................................. 48
4.4 Statistical Data Analysis ...................................................................... 55
CHAPTER 5 CONCLUSIONS ........................................................................... 65
APPENDIX ............................................................................................... 67
DESIGN OF EXPERIMENT–TEST SEQUENCE & RESULTS FOR
THE MODIFIED FINAL IMPACT TEST ......................................................... 67
REFERENCES ............................................................................................... 68
BIOGRAPHICAL SKETCH ............................................................................. 70
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Table 4-1 Distribution of cells per area on different foam types .................................................. 44
Table 4-2 Test results summary .................................................................................................... 45
Table 4-3 Sample types’ description ............................................................................................. 49
Table 4-4 Results from the impact tests ........................................................................................ 50
Table 4-5 Average tests results for impact tests ............................................................................ 52
Table 4-6 Absorbed energy according to the different thicknesses and conditions ...................... 54
Table 4-7 Experimental design ..................................................................................................... 56
Table 4-8 Analysis of Variance (ANOVA) for the Impact Energy response ............................... 57
Table 4-9 Test statistics for the Impact Energy response.............................................................. 57
Table 4-10 Analysis of Variance (ANOVA) for the total deflection response ............................. 60
Table 4-11 Tests statistics for the total deflection response model .............................................. 60
Table 4-12 Results of optimization of responses using Design Expert ........................................ 63
Table 4-13 Injury tolerances for human organs [20] ..................................................................... 64
Table A-1 DOE tests sequence & reported results ........................................................................ 67
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Figure 2-1 The range of properties available through foaming [8] ................................................. 5
Figure 2-2 Modulus diagram for a thermoset cross-linked polymer (epoxy) with Tg = 127°C ..... 8
Figure 2-3 Modulus diagram for a typical elastomer (PIB). Tg is about -70 C [8] ........................ 9
Figure 2-4 Stress-strain curve of a polymer showing the change in behavior as temperature
changes [8] ............................................................................................................................ 13
Figure 2-5 Compressive stress-strain curves for foams: (a) an elastomeric foam; (b) an elastic-
plastic foam; (c) an elastic-brittle foam [8] ........................................................................... 18
Figure 3-1 Compression test setup and images of samples during compression .......................... 31
Figure 3-2 Setup of the DMA compression test ............................................................................ 32
Figure 3-3 Instron Dynatup impact tester setup ............................................................................ 34
Figure 3-4 Desired failure mechanism of a 5-ply composite plate seen at plain sight ................. 34
Figure 3-5 Clamping and breaking configuration inside the impact tester ................................... 35
Figure 3-6 Location of the impact point with respect to the clamping system ............................. 35
Figure 3-7 Direct force transfer to rigid body (read from bottom towards the top) ...................... 36
Figure 3-8 Damper analysis (read from bottom towards the top) ................................................. 37
Figure 3-9 Damper failure analysis (read from bottom towards the top)...................................... 37
Figure 3-10 Impact tester 2-D analyses......................................................................................... 38
Figure 3-11 Load transfer upon impact on a real-case scenario ................................................... 39
Figure 3-12 Setup of wood box inside of the clamping device of the impact tester ..................... 39
Figure 3-13 Side view analysis of the impact with the wood support incorporated ..................... 40
Figure 4-1 SEM photograph of sectioned Air2Gel HD foam viewed along the foam rise
direction, showing equiaxed cells ......................................................................................... 42
Figure 4-2 Single cell at an X700 magnification. As observed, two types of holes were found: in
a face on a sectioned cell, in a face on a deeper non-sectioned cell, and several face holes
joined by an edge fracture ..................................................................................................... 43
Figure 4-3 Stress-Strain curve for tensile test on ShockTEC Air2Gel 1.25 mm (1/8 in) foam
samples .................................................................................................................................. 45
Figure 4-4 Compressive load vs. thickness of the specimen......................................................... 47
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Figure 4-5 Dynamic Mechanical Analyzer Test results for Air2Gel HD blue foam at 1 Hz
frequency ............................................................................... (cid:5)(cid:16)(cid:16)(cid:17)(cid:16)(cid:18)(cid:6)(cid:3)(cid:17)(cid:17)(cid:19)(cid:20)(cid:21)(cid:16)(cid:19)(cid:6)(cid:22)(cid:17)(cid:23)(cid:6)(cid:24)(cid:25)(cid:26)(cid:27)(cid:22)(cid:25)(cid:24)(cid:28)
Figure 4-6 Impact load histories for the glass laminate ................................................................ 53
Figure 4-7 Load-deflection curve of the glass laminate ................................................................ 53
Figure 4-8 Impact energy histories of the glass laminates ............................................................ 54
Figure 4-9 Cause and effect diagram ............................................................................................ 55
Figure 4-10 Model statistics & diagnostics plots .......................................................................... 58
Figure 4-11 Factors interaction graph ........................................................................................... 59
Figure 4-12 Model graph associate with test statistics .................................................................. 61
Figure 4-13 Model interaction graph for the total deflection response ......................................... 62

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My gratitude goes to the High Performance Materials Institute (HPMI) for their financial
support, and Kemmler Products for supplying test materials. My deepest gratitude goes to all my
colleagues and personnel at HPMI for their help throughout the years. I would like to thank Dr.
Jonathan Colton and Mr. Robert Cooper for their assistance and the use of their testing facilities
at the Georgia Institute of Technology. I would also like to thank my professors at FAMU-FSU
College of Engineering for their guidance; my mentors, Dr. Okenwa Okoli, Dr. Ben Wang, and
Dr. Samuel Awoniyi for their continued support and encouragement during my research. Thank
you for your patience and for having faith in me. I also want to thank Dr. Yaw Owusu and Dr.
Richard Liang for motivating and introducing me into the world of guided research.
Finally, I would like to express my eternal debt to my family, especially my
grandparents, Olga and Joseph Schober for their unconditional love, and for expanding my
horizons by giving me the opportunity of studying abroad. I would like to thank my mother,
Maria Isabel, my aunts, Olga and Teresa, my uncle, Keith, and my sisters, Cristina and Michelle
for being my support system throughout the years. To Xenia and Naty for teaching me skills to
survive on my own. I also want to thank my friends, for becoming my second family during
college.
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The current research studied the idea of introducing energy-absorbing polymers –
specifically high-density viscoelastic polyurethanes – to reduce the blunt trauma from
residual impact energy. This work investigated the material properties of viscoelastic
polyurethane foams and the efficacy of the addition of an energy absorbing material to
protective garments for reducing blunt trauma under low-velocity impact. The research also
provided a methodology for testing composite plates backed by soft materials during low-
velocity impact tests. The thickness of the backing material was proven the most influential
factor in energy absorption during impact. Finally, using optimization tools, a suggested
thickness and bonding condition was given for the implementation of viscoelastic foam in
protective garments.

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Early forms of body protection included brine-soaked leather, the metal breastplates of
Roman soldiers, full suits of armor and chain mail in the Middle Ages, and military flak jackets
during World War II. The idea of a bulletproof vest dates from the early 20th century. The U.S.
Patent and Trademark Office lists records dating back to 1919 for various designs of bullet proof
vests and body armor type garments. One of the first documented instances where law
enforcement officers demonstrated such a garment for use was detailed in the April 2, 1931
edition of the Washington, D.C., Evening Star, where a bulletproof vest was demonstrated to
members of the Metropolitan Police Department. By the 1970s, DuPont had developed Kevlar
29, the first generation of bullet resistant fibers, and helped to make the production of flexible,
concealable body armor practical for the first time [1]. The National Law Enforcement and
Criminal Justice (NILECJ) began testing the fabric for use in body armor. Ever since the
introduction of Kevlar, several different types of Outer Tactical Vests (OTV’s) have been
designed and manufactured. In 2000, the body armor industry comprised over 80 manufacturers,
who together conducted $200 million in business per year. Although personnel armor protection
has been successful, it is still plagued by issues of blunt trauma. The sporting world is also
besieged with similar issues of blunt trauma.
Blunt trauma is the damage to the body after a high-energy impact, such as the impact of
a projectile. Blunt trauma can still happen, even if the projectile does not perforate the
individual’s body. The subject can suffer from light trauma, such as a bruise, to severe organ
damage, which may lead to fatality [2].
Since the human body is susceptible to even small amounts of impact energy, the need to
provide cushioning becomes imperative. The utilization of composite panels in the Small Arm
Protective Insert (SAPI) has yielded in improved energy absorption [2]. The current work
reviewed methodologies for increased protection against non-penetrative impact induced trauma.
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