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THE VELOCITY IMPACT RESPONSE OF FILLED AND UNFILLED POLYPROPYLENE HONEYCOMB CORE SANDWICH STRUCTURE
MOHAMAD IBRAHIM BIN AHMAD
UNIVERSITI SAINS MALAYSIA
2016
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THE VELOCITY IMPACT RESPONSE OF FILLED AND UNFILLED POLYPROPYLENE HONEYCOMB CORE
SANDWICH STRUCTURES
by
MOHAMAD IBRAHIM BIN AHMAD
Thesis submitted in fulfillment of the requirements for the degree of
Master of Science
August 2016
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ACKNOWDLEDGMENT
Bismmillahirrahmanirrahim,
In the name of Allah, the Most Beneficent, the Most Merciful.
First of all, I would like to thank my Supervisor Prof. Hazizan Md Akil, for his wisdom, knowledge and guidance during my studies.
I am also grateful to Advanced Materials Research centre (AMREC) SIRIM Berhad for giving the opportunity to further my studies. Not forgetting my Head Section, Senior Researcher Dr. Mohd Asri bin Selamat and my colleagues, Azman bin Hashim, Mohd Fadzlee bin Zainal Abidin for their kindness and support.
Special thanks, to the Dean, Deputy Deans, technicians and staff of School of Materials and Mineral Resources Engineering, USM. In addition, I would like to thank Mohd Hafiz bin Zamri, for his contributions.
My never ending gratitude to my family, my late father, Ahmad bin Said. To my beloved mother, my brother and sisters, Salmiah binti Ismail, Massita binti Ahmad, Omar bin Ahmad, Fatimah binti Ahmad, Salmah binti Ahmad and Habibah binti Ahmad for their moral support.
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I am also grateful to my best friend, Ahmad Makarimi bin Abdullah and to all my relatives for standing by me. Lastly, my appreciation goes to anyone who has been directly or indirectly involved in the completion of my research.
Mohamad Ibrahim bin Ahmad 2016
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TABLE OF CONTENTS
Page ACKNOWLEDGEMENT...………
TABLE OF CONTENTS...………..
LIST OF TABLES……….……….…….
LIST OF FIGURES…………..………
LIST OF PLATES………
LIST OF ABBREVIATIONS………..
LIST OF SYMBOLS..……….
ABSTRAK………...
ABSTRACT………
CHAPTER ONE : INTRODUCTION
1.1 Background………
1.2 Problem Statement………...
1.3 Research Objective………
1.4 Scope of the Project……….…………..
CHAPTER TWO : LITERATURE REVIEW
2.1 Introduction………
2.2 Fiber Reinforced Polymer (FRP)……….
2.2.1 Fiberglass facesheet ………
2.3 Matrices.……….….………
2.3.1 Thermosetting Resins ……….………
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1 3 4 4
6 7 7 8 9
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2.4 Adhesive………...
2.5 Foam ..………..………...…
2.5.1 The foam characteristic..……….
2.6 Fiberglass laminate structure .……..………..…...
2.7 The skin effect……….……….…….
2.8 Polypropylene core .……….……….…..
2.8.1 The core effect ………...…….………...
2.9 Honeycomb ..…………...………..….……….….……
2.10 Preparation of characterize specimen ………..……
2.10.1 Density measurement .………..……
2.10.2 Flexural test..………...………
2.10.3 Indentation test.………...
2.10.4 Compression test….…….……….…….
2.10.5 Impact test.……….……….
2.10.6 Shear test………….……….…...……
CHAPTER THREE : MATERIALS AND METHODOLOGY
3.1 Introduction……….…….………
3.2 Raw Material..………..……
3.2.1 Polypropylene (PP) honeycomb core…..…….………..
3.2.2 Polyurethane foam ………..………...
3.2.3 The skin materials ……….…
3.2.3.1 Glass fiber reinforced polymer ……….
3.3 Manufacture of polypropylene composite honeycomb sandwich
10 10 11 11 12 13 14 14 16 16 17 19 21 22 23
26 26 26 27 27 27
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structure………..……….
3.3.1 Density ……….………..…………
3.4 Mechanical properties of the structure ……….………
3.4.1 Flexural Test… ..………..………..…….………
3.4.1.1 Determination of bending stiffness, D and shear
modulus, G of the sandwich structure..………….……..
3.4.2 Indentation Test ……….……….
3.4.3 Compression Test ……….……..
3.4.4 Low Impact Test………
3.5 Ultrasonic Imaging..………
CHAPTER FOUR : RESULT AND DISCUSSION
4.1 Density ..………..
4.2 The Flexural ……….
4.3 The Indentation..……….
4.4 The Compression..……….………...
4.5 Impact Response...……….……….…..
4.6 Ultrasonic C-Scan …..……….………
4.6.1 Flexural Damage Area ………...……….…….…………..
4.6.2 Indentation Damage Area ……….……….
4.6.3 Compression Damage Area ……….…….….……….….………….
4.6.4 Impact Damage Area ……….….….………..
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32 35 37 38 40
42 45 51 54 57 59 59 68 76 83
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CHAPTER FIVE : CONCLUSION AND SUGGESTION
5.1 Conclusion ………
5.1.1 The thickness effect for filled and unfilled polypropylene honeycomb core and the performance for filled and unfilled polypropylene honeycomb core under mechanical performance…
5.1.2 Damage area..……….
5.2 Suggestion…..……….
REFERENCES………..
APPENDICES APPENDIX A APPENDIX B
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LIST OF TABLES
Page
Table 2.1 Table 3.1
Table 3.2
Table 4.1
Table 4.2
Table 4.3
Table 4.4
Table 4.5
Table 4.6
Table 4.7
Table 4.8
Mechanical properties of glass fiber
Summary of the mechanical properties of the glass fiber
Details of instrumented drop – weight impact test
The density of the polypropylene honeycomb filled and unfilled sandwich structure, 30 mm and 40 mm thickness
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59 The density of Polypropylene honeycomb filled and unfilled sandwich structure 30 mm and 40 mm thickness with maximum energy during testing
Maximum load at various displacement rates
The values of 1/48D and 1/4AG of the 30 mm and 40 mm polypropylene honeycomb filled and unfilled sandwich structure
The values of n of the 30 mm and 40 mm polypropylene honeycomb filled and unfilled sandwich structure
The values of C of the 30 mm and 40 mm Polypropylene honeycomb filled and unfilled sandwich structure
Compression; The values of maximum stress of the 30 mm and 40 mm 30 mm and 40 mm PP honeycomb unfilled sandwich structure and 30 mm and 40 mm PP-honeycomb filled foam sandwich structure
Impact; The values of maximum energy absorbed by 30 mm and 40 mm filled and unfilled Polypropylene honeycomb sandwich structure
ix Table 4.9
Table 4.10
Table 4.11
Table 4.12
Table 4.13
Table 4.14
Table 4.15
Flexural; Damage area for 30 mm Polypropylene honeycomb unfilled sandwich structure and Polypropylene honeycomb filled sandwich structure at various displacement rates
Flexural; Damage area for 40 mm Polypropylene honeycomb unfilled sandwich structure and Polypropylene honeycomb filled sandwich structure at various displacement rates
Indentation; Damage area for 30 mm Polypropylene honeycomb unfilled sandwich structure and Polypropylene honeycomb filled sandwich structure at various displacement rates
Indentation; Damage area for 40 mm Polypropylene honeycomb unfilled sandwich structure and Polypropylene honeycomb filled sandwich structure at various displacement rates
Compression; Damage area for 30 mm Polypropylene honeycomb unfilled sandwich structure and Polypropylene honeycomb filled sandwich structure at various displacement rates
Compression; Damage area for 40 mm Polypropylene honeycomb unfilled sandwich structure and Polypropylene honeycomb filled sandwich structure at various displacement rates
Damage area for 30 mm and 40 mm Polypropylene honeycomb unfilled sandwich structure and Polypropylene honeycomb filled sandwich structure at various impact energy
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LIST OF FIGURES
Page Figure 1.1
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.4
Figure 3.5
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
A composite sandwich panel
Flow chart shows the methodology of fabrication and mechanical determination behavior of polypropylene honeycomb
The cross section of the sandwich structure
The plot of value of 1/48D and 1/4AG in determination of the value shear modulus for sandwich structure
Schematic plot of Log P versus Log α to determine the value of n
Schematic of the impact arrangement
The load-displacement of Polypropylene honeycomb sanwdich structure; 40 mm thickness at displacement rate 500 mm/min
The maximum load hold by 30 mm and 40 mm Polypropylene honeycomb unfilled sandwich structure, 30 mm and 40 mm Polypropylene honeycomb filled sandwich structure at different displacement rates
Flexural Modulus of 30 mm and 40 mm Polypropylene honeycomb unfilled sandwich structure, 30 mm and 40 mm Polypropylene honeycomb filled sandwich structure at different displacement rate
Shear modulus of 30 mm and 40 mm Polypropylene honeycomb unfilled sandwich structure, 30 mm and 40 mm Polypropylene honeycomb filled sandwich structure at different displacement rate
(a) 30 mm, (b) 40 mm core thickness indentation graph at rate 2
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xi Figure 4.6
Figure 4.7
Figure 4.8
Figure 4.9
Figure 4.10
Figure 4.11
Figure 4.12
Figure 4.13
Figure 4.14
500 mm/min
Nominal stress versus strain curves of 40 mm Polypropylene honeycomb unfilled sandwich structure under compression test at rate 100 mm/min
Flexural; The 30 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Flexural; The 40 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Flexural; The 30 mm and 40 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Indentation; The 30 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Indentation; The 40 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Indentation; The 30 mm and 40 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Compression; The 30 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Compression; The 40 mm PP-honeycomb sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
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Figure 4.16
Figure 4.17
Figure 4.18
Compression; The 30 mm and 40 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure damage area at various stress load
Damage area of 30 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled sandwich structure with impact energy
Damage area of 40 mm PP-honeycomb unfilled sandwich structure and PP-honeycomb filled foam sandwich structure with impact energy
Impact; Damage area of 30 mm and 40 mm PP-honeycomb unfilled sandwich structure, PP-honeycomb filled sanwich structure
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LIST OF PLATES
Page
Plate 2.1 Plate 2.2 Plate 3.1
Plate 3.2
Plate 3.3
Plate 4.1
Plate 4.2
Plate 4.3
Plate 4.4
Plate 4.5
Plate 4.6
Plate 4.7
Polypropylene honeycomb structure Polypropylene honeycomb cores
Stress-load following displacement rate on Polypropylene honeycomb unfilled sandwich structure core panel during flexural test
Polypropylene honeycomb unfilled sandwich structure for indentation test at displacement rate 100 mm/min
40 mm Polypropylene honeycomb unfilled sandwich structure under compression test at rate 100 mm/min
Specimen of 30 mm thickness Polypropylene honeycomb unfilled sandwich structure under variety displacement rate
Specimen of 30 mm thickness Polypropylene honeycomb unfilled sandwich structure under impact energy of 10.31 Joule
30 mm PP-honeycomb unfilled sandwich structure, core damage
The 40 mm polypropylene honeycomb after flexural test at various displacement rates
The 40 mm polypropylene honeycomb filled sandwich structure after flexural test
The 40 mm polypropylene honeycomb unfilled sandwich structure during flexural test
Flexural; C-scan images of 30 mm Polypropylene honeycomb unfilled sandwich structure under various displacement rate (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500mm⁄min
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xiv Plate 4.8
Plate 4.9
Plate 4.10
Plate 4.11
Plate 4.12
Plate 4.13
Plate 4.14
Plate 4.15
Plate 4.16
Plate 4.17
Flexural; C-scan images of 30 mm Polypropylene honeycomb filled under various displacement rates (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Flexural; C-scan images of 40 mm Polypropylene honeycomb unfilled sandwich structure under various displacement rate (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Flexural; C-scan images of 40 mm Polypropylene honeycomb filled under various displacement rates (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
The 30 mm polypropylene honeycomb after indentation test at various displacement rates
Indentation; C-scan images of 30 mm Polypropylene honeycomb sandwich unfilled structure under various
displacement rate (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Indentation; C-scan images of 30 mm Polypropylene
honeycomb filled under various displacement rates (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Indentation; C-scan images of 40 mm Polypropylene honeycomb unfilled sandwich structure under various
displacement rate (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Indentation; C-scan images of 40 mm Polypropylene
honeycomb filled under various displacement rates (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
The 40 mm polypropylene honeycomb unfilled sandwich structure after compression test at various displacement rates
Compression; C-scan images of 30 mm Polypropylene honeycomb unfilled sandwich structure under various
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xv Plate 4.18
Plate 4.19
Plate 4.20
Plate 4.21
Plate 4.22
Plate 4.23
Plate 4.24
Plate 4.25
displacement rate (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Compression; C -scan images of 30 mm Polypropylene honeycomb filled under various displacement rates (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Compression; C -scan images of 40 mm Polypropylene honeycomb unfilled sandwich structure under various displacement rate (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
Compression; C -scan images of 40 mm Polypropylene honeycomb filled under various displacement rates (a) Control (b) 1 mm⁄min, (c) 10 mm⁄min, (d) 100 mm⁄min, (e) 500 mm⁄min
The 40 mm polypropylene honeycomb after impact test
Comparison of c-scan images of 30 mm Polypropylene honeycomb unfilled sandwich structure under various impact energy, (a) Control (b) 7.356 J, (c) 8.838 J, (d) 10.311 J, (e) 11.784 J, (f) 13.257 J
Comparison of c-scan images of 30 mm Polypropylene honeycomb filled sandwich structure under various impact energy, (a) Control (b) 7.356 J, (c) 8.838 J, (d) 10.311 J, (e) 11.784 J, (f) 13.257 J
Comparison of c-scan images of 40 mm Polypropylene honeycomb unfilled sandwich structure under various impact energy, (a) Control (b) 7.356 J, (c) 8.838 J, (d) 10.311 J, (e) 11.784 J, (f) 13.257 J
Comparison of c-scan images of 40 mm P Polypropylene honeycomb filled sandwich structure under various impact energy (a) Control (b) 7.356 J, (c) 8.838 J, (d) 10.311 J, (e) 11.784 J, (f) 13.257 J
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LIST OF ABBREVIATIONS
FRP Fiber reinforced polymer
PP Polypropylene
PVC Polyvinyl chloride
UTM Universal Testing Machine
ASTM American Society for Testing and Materials NDT Non-Destructive Testing
ss Sandwich structure
hc Honeycomb core
ff Foam filled
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LIST OF SYMBOLS
kg Kilogram
m Meter
kg/m3 Density
Mpa Megapascal
N Newton
Nm2 Newton meter square KHz Kilo Hertz
mm Milimeter
g Gram
ms Milisecond
min Minute
Ef Flexural modulus
P Force
k Contact stiffbess δ Displacement rate
α Indentation
E Young modulus
C Contact parameter n Contact parameter
m Mass
v Velocity
t Time
s Second
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L Span length
J Joule
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KESAN IMPAK KE ATAS STRUKTUR TERMOPLASTIK TERAS TERAPIT YANG KOSONG DAN TERISI
ABSTRAK
Kajian ini mensasarkan penilaian prestasi termoplastik terapit yang berbeza ketebalan, terisi dan tidak terisi dengan buih poliuretena. Ketumpatan setiap struktur teras terapit direkod sebelum ujian impak hentaman halaju rendah, ujian ketumpatan, ujian lentur, ujian mampatan dan ujian lekuk dilakukan. Ujian imbasan dilakukan ke atas sampel selepas ujian mekanikal dijalankan. Buih poliuretena yang diisi ke dalam sel-sel teras terapit telah meningkatkan ketumpatan teras terapit antara 30 hingga 34 peratus dari ketumpatan asal.
Dalam ujian lenturan, kehadiran buih poliuretana telah meningkatkan kadar penyerapan tenaga sebanyak 15 hingga 38 peratus untuk teras berketebalan 30 mm dan 6 hingga 17 peratus untuk teras berketebalan 40 mm. Dari ujian lekuk didapati nilai n adalah 1.52 hingga 1.87 untuk teras terapit 30 mm dan 0.33 hingga 1.27 untuk teras terapit 40 mm.
Nilai n yang diterima untuk komposit adalah 1.5. Nilai kekukuhan C bergantung kepada kekuatan kekenyalan plastik buih poliuretena serta sifat lapisan atas dan bawah. Nilai C adalah di antara (0.90 hingga 1.56)x106 N/mn. Dalam ujian mampatan teras terapit 30 mm dan 40 mm berisi buih poliuretana menunjukkan peningkatan tenaga antara 10 hingga 30 peratus. Manakala dalam ujian impak hentaman halaju rendah teras terapit yang terisi buih poliuretana mampu menyerap lebih tenaga berbanding teras terapit kosong. Kadar kerosakan yang berlaku ke atas permukaan lapisan dipengaruhi oleh kadar penerimaan tenaga semasa berlaku hentakan. Kehadiran buih poliuretana telah membantu menyerap sebahagian tenaga yang dikenakan ke atas teras terapit dan ini menyebabkan kurangnya berlaku kerosakan pada permukaan lapisan atas kulit.
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THE VELOCITY IMPACT RESPONSE OF FILLED AND UNFILLED POLYPROPYLENE HONEYCOMB CORE SANDWICH STRUCTURE
ABSTRACT
In this study, the performance of polypropylene honeycomb structure with different thickness, filled and unfilled was investigated. The density of the specimen was measured and subjected to flexural test, indentation test, compression and the low velocity impact test. After each test, the specimen was scanned under ultrasonic C- scan to investigate the effect of energy on the honeycomb panel structure. Introducing reinforced material into honeycomb cell increases the density of the panel structure up to 30 - 34% of initial density. Based on the flexural study, the percentage of energy increment for structure to collapse is around 15 to 38 percent for 30 mm core thickness and 6 to 17 percent for 40 mm core thickness. In indentation test, the n value is between 1.52 to 1.87 for 30 mm core thickness and 0.33 to 1.27 for core thickness 40 mm; 1.5 is the value for an acceptant for composite. The stiffness C was found to depend on the plastic collapse strength of the polyurethane foam and the properties of the skin.
The value is between (0.90 to 1.56) x106 N/mn. In compression test, reinforced Polypropylene honeycomb filled sandwich structure has better energy absorption characteristic rather than Polypropylene honeycomb unfilled sandwich structure. In low velocity impact test, the reinforced effect increased the energy absorbtion efficienty about 10 to 30 percentage for both 30 mm and 40 mm core thickness. The damage area for all specimens for the Polypropylene honeycomb unfilled sandwich structure much higher compared to reinforce structure. The reinforced material acted to reduce the stress on the facing skin of the honeycomb structure.
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CHAPTER ONE INTRODUCTION
1.1 Background
In marine engineering, the engineer and the developer are looking for material that has good strength to weight stiffness, costly, easy to handle for structure engineering.
Normally, the honeycomb used is made from aluminum. Others type used are aramide and nomex honeycomb. These types of materials are light, strong, expensive but brittle. In fabricating a structure for intermediate application in some part of interior structure is not significant.
The use of honeycomb design in this field is very effective due to the honeycomb produces the most efficient strength – to – weight and stiffness – to – weight structure attainable and very useful in fabricating lightweight structures.
Polypropylene honeycomb was introduced in 1980 by extrusion process and now are applied in many engineering industries, such as in marine application; internal furniture, automotive; panel for door, roof, energy field; blades, architectural; panels for door, floor and wall for clean room, recreational; canoes, industrial construction;
floating roofs and landscaping; gravel.
Polypropylene honeycomb that is made from thermoplastic, has characteristics such as light weight, good ratio of stiffness-strength, vibration and sound dampening, good in absorption of energy, resistant to chemical, corrosion, fungi, moisture and rot and easy to assemble.
Two countermeasures, addition of non-woven polyester tissue and polypropylene
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film were added and have been taken for a better performance of the polypropylene core. Both sides of the polypropylene honeycomb core surface were laminated with non-woven polyester tissue. The other function of adding the tissue is to create better bonding with other honeycomb panel if necessary. Besides the tissue, polypropylene film was added under the non-woven tissue. The film function is as a barrier to avoid resin goes into the core and at the same time save resin consumption.
The core structure is typically 'sandwiched' between face sheets normally known as
‘skin’. Polyester and hardener are applied to from fiberglass skin. The fiberglass sheets ware attached to the honeycomb core with a bonding adhesive such as polyester mix with suitable hardener or any combination of resin in epoxy systems. This is to ensure homogenous contact of resin between the face sheet and the polypropylene honeycomb core.
Figure 1.1 is a diagram of polypropylene honeycomb panel fabrication and its basic materials; face sheets, adhesive and core structure (reinforce material: polyurethane foam).
Figure 1.1: A composite sandwich panel
http://www.berlystone.com/js/htmledit/kindeditoren/attached/20150331/2015033119 4239_65631.jpg (18 May 2015)
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In this research, the honeycomb with thickness of 30 mm and 40 mm made of polypropylene materials were suggested as an alternative to be used as a material in construction of simple part in marine interior design. The study has introduced polypropylene honeycomb core and polypropylene honeycomb core reinforce with polyurethane. Polyurethane foam was filled into every core cell for both thicknesses.
These polypropylene honeycomb 30 mm and 40 mm filled and unfilled will be assembled under vacuum bagging technique.
Complete polypropylene honeycomb structure has good elastic and also good stiffness.
Reinforce foam into polypropylene core was believed to improve the elastic, stiffness properties and increase the total load receive by honeycomb core structure.
The main reason for using the polypropylene honeycomb is due to its stiffness and light weight. In choosing the core structure five criteria of failure modes when loading are considered. The failure modes are shear core failure, tensile core failure, tensile face yielding, bonding failure between the skin and the core compression face buckling and indentation possibility at the loading points of the faces and core structure.
1.2 Problem Statement
In interior design of small boat, the engineers attempt to find a material with low cost of production with suitable characteristics such as easy to use and handle, as well as appropriate level of stiffness, strength and light. Aluminum honeycomb core is light and strong but expensive and brittle. While aramid fiber honeycomb core is also strong, corrosion resistant but brittle. The advantages of polypropylene are light, corrosion resistant, and elastic and has high stiffness.
