Hybrid Composite Wires for Tensile Armour in Flexible Risers

190 Pages·2017·9.26 MB·English

by  Mayank Gautam

Hybrid Composite Wires for Tensile
Armour in Flexible Risers

A thesis submitted to The University of Manchester for the degree of
Doctorate of Philosophy
In the faculty of Science and Engineering

September 2016

Mayank Gautam
Textile Composite Group
School of Materials
Table of Contents
Table of Contents
Table of Contents ......................................................................................................... 1
List of Figures .............................................................................................................. 6
List of Tables.............................................................................................................. 11
Thesis Abstract ........................................................................................................... 12
Declaration ................................................................................................................. 13
Copyright Statement .................................................................................................. 14
Acknowledgements .................................................................................................... 15
Introduction ............................................................................................... 16
1.1. Introduction to flexible risers ...................................................................... 16
1.2. Research motivations and rationale ............................................................. 17
1.3. Hybrid composite wires ............................................................................... 18
1.4. Research disseminations .............................................................................. 21
1.5. Outline of the thesis ..................................................................................... 22
Review of Literature .................................................................................. 24
2.1. Flexible risers .............................................................................................. 24
2.1.1. Types of risers ...................................................................................... 25
2.1.2. Composition of flexible riser ............................................................... 26
2.1.2.1. Carcass ....................................................................................... 26
2.1.2.1. Pressure sheath ........................................................................... 27
2.1.2.2. Pressure armour .......................................................................... 27
2.1.2.3. Tensile armour ........................................................................... 29
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Table of Contents
2.1.2.4. Anti-wear layers ......................................................................... 29
2.1.2.5. Anti-buckling layer and outer sheath ......................................... 29
2.1.2.6. Carbon steel ................................................................................ 31
2.1.3. Design process for flexible risers ......................................................... 32
2.1.4. Failure modes in flexible risers ............................................................ 32
2.1.5. Failure modes of flexible riser due to tensile armours ......................... 35
2.1.5.1. Defects due to manufacturing processes .................................... 35
2.1.5.2. Tensile fatigue ............................................................................ 36
2.1.5.3. Buckling ..................................................................................... 37
2.2. Composites .................................................................................................. 39
2.2.1. Unidirectional composite manufacturing: pultrusion .......................... 43
2.2.2. Composites in marine applications ...................................................... 44
2.2.3. Composites in risers ............................................................................. 44
2.3. Braiding ....................................................................................................... 46
2.3.1. Braid geometric and structural parameters .......................................... 48
2.3.1.1. Braid angle and braid cover ....................................................... 48
2.3.1.2. Braid crimp................................................................................. 51
2.3.1.3. Braid topology ............................................................................ 52
2.3.2. Mechanical properties of braid (non-infused state) ............................. 53
2.4. Braidtrusion ................................................................................................. 54
2.5. Summary ..................................................................................................... 55
Study of Manufacturing Processes for Hybrid Wire Composite Wires .... 57
3.1. Material specification and properties ........................................................... 57
3.1.1. Quality of composite rods ...................................................................... 59
3.2. Manufacturing process for hybrid composite wire ....................................... 61
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Table of Contents
3.2.1. Over-braiding process: Pack with Ф 2 mm rods ................................... 65
3.2.2. Over-braiding process: Pack with Ф 4 mm rods ................................... 65
3.3. Measurement process: Braid structural parameters ...................................... 68
3.3.1. Braid angle ............................................................................................. 68
3.3.2. Braid thickness ....................................................................................... 70
3.3.3. Tow width .............................................................................................. 72
3.3.4. Braid crimp ............................................................................................ 73
3.4. Results: Braid parameters ............................................................................. 74
3.4. Theoretical and experimental braid cover factor .......................................... 75
3.4. Quantification of the tow tension during the braiding process .................... 78
3.4. Summary ...................................................................................................... 84
Mechanical Testing and Characterisation of Hybrid Composite Wires .... 85
4.1. Mechanical tests procedures ......................................................................... 85
4.1.1. Flexure tests ........................................................................................... 85
4.1.2. Torsion tests ........................................................................................... 89
4.1.3. Tensile tests for single rods ................................................................... 92
4.2. Mechanical characterisation ......................................................................... 92
4.2.1. Axial and in-plane shear modulus of single rods ................................... 92
4.2.2. Flexural behaviour ................................................................................. 94
4.2.2.1. Effect of point load......................................................................... 97
4.2.2.2. Effect of boundary conditions ........................................................ 99
4.2.3. Torsional behaviour ............................................................................. 101
4.3. Comparison of hybrid composite wires with traditional metallic armour wires
.............................................................................................................................. 105
4.3.1. Corrosion ............................................................................................ 105
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4.3.2. Flexural and torsional stiffness ........................................................... 105
4.3.2.1. Comparison with traditional metallic tensile armour wires. ............ 106
4.3.2.2. Comparison with metallic structures with similar dimensions ........ 107
4.3.3. Behaviour under through thickness compression ............................... 107
4.4. Summary .................................................................................................... 108
Multi-scale Modelling of Hybrid Composite Armour Wires .................. 109
5.1. Introduction ................................................................................................ 109
5.2. Methodology for multiscale modelling ...................................................... 111
5.2.1. Elastic properties of composite rods .................................................... 111
5.2.2. Braid shell properties: meso-mechanical analytical model ................. 114
5.2.3. Computational modelling: finite element model ................................. 120
5.2.3.1. Geometry and mesh...................................................................... 120
5.3.3.2. Mesh sensitivity study .................................................................. 121
5.3.3.3. Interaction properties ................................................................... 123
5.3.3.4. Boundary conditions .................................................................... 126
5.3. Results and observations ............................................................................ 129
5.3.1. Torsional behaviour ............................................................................. 129
5.3.2. Flexural behaviour ............................................................................... 134
5.5. Summary .................................................................................................... 145
Parametric Studies Using Multiscale Model ........................................... 147
6.1. Introduction ................................................................................................ 147
6.2. Effect of friction ......................................................................................... 147
6.3. Effect of model length ................................................................................ 149
6.4. Different combinations of material systems ............................................... 151
6.5. Summary .................................................................................................... 156
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Table of Contents
Conclusions and Directions for Future Research .................................... 157
7.1. Manufacturing study ................................................................................... 157
7.2. Mechanical characterisation ....................................................................... 158
7.3. Multi-scale model and parametric studies .................................................. 160
7.4. Recommendations for future work ............................................................. 162
Bibliography ............................................................................................................. 163
Appendix .................................................................................................................. 174

Word Count: 45,235
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List of Figures
List of Figures
Figure 1.1: Comparison between two flexible risers with (a) metallic tensile armour
wires, and (b) hybrid composite tensile armour wire ................................................. 19
Figure 1.2: Different configurations of hybrid wires studied in thesis ...................... 20
Figure 1.3: Conceptual representation of types of tensile armour wires: (a) traditional
carbon steel, (b) line packed circular composite rods held together by over-braid
sleeve, (c) carbon reinforced composite strip, (d) carbon reinforced composite strips
stacked in the form of packed cards held together by over-braid sleeve, and (e)
hexagonal packed circular composite rods held together by over-braid sleeve (studied
in this thesis) .............................................................................................................. 21
Figure 1.4: Schematic representation of the outline of thesis .................................... 22
Figure 2.1: Carcass of a flexible riser [15] ................................................................. 26
Figure 2.2: Zeta interlock layer for pressure armour [16] .......................................... 27
Figure 2.3: Composition of a typical flexible riser .................................................... 28
Figure 2.4: Fabrication process of tensile armour [13, 22] ........................................ 30
Figure 2.5: Failure of flexible risers due to: (a) failure of external sheath [22] (b)
collapse of carcass [13] .............................................................................................. 33
Figure 2.6: Failure of flexible risers due to corrosion of tensile armour wires from H2S
and CO2 [22, 35] ........................................................................................................ 34
Figure 2.7: Failure of tensile armour wires due to tensile fatigue [39] , .................... 36
Figure 2.8: Failure of tensile armour wires due to radial buckling [45] .................... 37
Figure 2.9: Failure of tensile armour wires due to lateral buckling [47]. .................. 38
Figure 2.10: Schematic representation of a unidirectional fibre reinforced composite
with a: (a) 3-D view and (b) 2-D cross-sectional view .............................................. 39
Figure 2.11 : Molecular structure of ethylene and of ultra-high–molecular-weight
polyethylene (UHMW-PE), where n is the degree of polymerization ....................... 41
Figure 2.12: Molecular chain distribution of: (a) thermoplastic polymer, and (b)
thermoset polymer obtained from [61] ...................................................................... 42
Figure 2.13: Typical pultrusion machine obtained from [70] .................................... 43
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List of Figures
Figure 2.14: Flexible riser with (a) steel armour, and (b) composite armour shown in
[80] ............................................................................................................................. 45
Figure 2.15: Schematic representation of parts of a maypole braiding machine: (a)
deck, (b) carrier with mounted bobbin ....................................................................... 47
Figure 2.16: Computer aided drawing using TexGen software [89] of a braid with 45⁰
braid angle depicting: (a) braid angle, (b) braid unit cell, and (c) braid crimp .......... 49
Figure 2.17: Most commonly used braid topologies: (a) Diamond (1/1), (b) Regular
(2/2), and (c) Hercules (3/3) ....................................................................................... 52
Figure 2.18: A typical load–extension curve of a biaxial braided structure [103] ..... 53
Figure 2.19 : Arrangement of braiding-pultrusion process obtained from [105] ....... 54
Figure 3.1: Process of measurement of density of composite rod in (a) & (b), and braid
fibres in (c) & (d) ....................................................................................................... 58
Figure 3.2: Scanning electron micro-graphs of cross-section of Ф 4 mm rod ........... 59
Figure 3.3: Optical micrographs showing alignment of fibres along the length of
pultruded composite rods with (a) & (b) Ф 2 mm, and (c) & (d) Ф 4 mm ................ 60
Figure 3.4: Different configurations of hybrid composite tensile armour wires Note -
HCW: Hybrid composite wires; θ is the braid angle. ................................................ 62
Figure 3.5: Hybrid composite tensile armour wire manufacturing processes ............ 63
Figure 3.6: Reverse braiding and braid jamming phenomenon. ................................ 66
Figure 3.7: Braiding at low carrier tension of only 50 grams .................................... 68
Figure 3.8: Braid angle measurement through: (a) digital protractor and (b) image
analysis. . .................................................................................................................... 69
Figure 3.9: Process of braid thickeness measurement using: (a) circumference of the
hybrid composite wires and (b) thickness of hybrid composite wires ....................... 71
Figure 3.10: Schematic of cross-section of hybrid composite wire showing different
thicknesses of components ......................................................................................... 72
Figure 3.11: Process of measurement of tow width using image analysis software .. 72
Figure 3.12: Schematic representation of the crimp determination process .............. 73
Figure 3.13: Theoretical and experimental cover factor for hybrid armour wires with
Ф 4 mm rods, using 12 carriers on a 24 carrier braiding machine (containing the
images of the hybrid wires) ........................................................................................ 76
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List of Figures
Figure 3.14: 2-D Schematic representation of tension mechanism during braiding
process using just two carriers ................................................................................... 79
Figure 3.15: Schematic representation of different cases of tow tension that may be
encountered during the braiding process.................................................................... 81
Figure 3.16: Schematic representation of methodology used for calculating coefficient
of friction using braid carriers .................................................................................... 82
Figure 4.1: Flexural tests being conducted on hybrid composite wire using: (a) three
point flexural test (for hybrid wires with Φ 2 mm rods), (b) four point flexural test (for
hybrid wires with Φ 2 mm rods), (c) three point flexural test (for hybrid wires with Φ
4 mm rods), and (d) four point flexural test (for hybrid wires with Φ 4 mm rods) ... 88
Figure 4.2: Torsion test to maximum limit of 40° twist angle for: (a) hybrid wire (45°
braid angle) with Ф 2 mm rods and (b) hybrid wire (45° braid angle) with Ф 4 mm
rods ............................................................................................................................. 91
Figure 4.3: Four point flexural test on hybrid composite wires (with Ф 4 mm rods and
regular braid topology) for: (a) 30° and (b) 45° braid angle ...................................... 95
Figure 4.4: Failed single rods during flexural test for (a) Ф 2 mm rod, (b) 4 mm
diameter rod, (c) micrograph of the cross-section of fractured Ф 4 mm rod, at the
point loads .................................................................................................................. 96
Figure 4.5: Flexural behaviour of hybrid wires and individual rods for: (a) Ф 2 mm
rods and (b) Ф 4 mm rods ......................................................................................... 98
Figure 4.6: Effect of edge boundary conditions ......................................................... 99
Figure 4.7: Effect of boundary condition for hybrid wire with Ф 4 mm rods: (a) without
braid (taped edges), (b) without braid (bonded edges), (c) with braid (45°, 2/2, taped
edges), and (d) with braid (45°, 2/2, non-bonded edges) ......................................... 100
Figure 4.8: Torsional behaviour of hybrid wires and individual rods for: (a) Ф 2 mm
rods and (b) Ф 4 mm rods ........................................................................................ 103
Figure 4.9: Comparison between different structures using: (a) flexural rigidity and (b)
torsional rigidity ....................................................................................................... 106
Figure 5.1: Schematic representation of the process for multi-scale modelling of
hybrid composite armour wires ................................................................................ 110
Figure 5.2: Schematic representation of material coordinates of pultruded composite
rods, with fibre axis as “1” direction ........................................................................ 112
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List of Figures
Figure 5.3: (a) Material orientation for composite rod, (b) material orientation for shell,
and (c) mesh for the model....................................................................................... 120
Figure 5.4: The different number of elements used to carry out the mesh sensitivity
study on multiscale model for hybrid composite wires with Ф 4 mm rods ............. 122
Figure 5.5: Mesh density sensitivity study for flexural and torsional mode of
deformation for hybrid wire assembly with Ф 4 mm rods ....................................... 123
Figure 5.6: Micrographs of cross-section of composite rod with Ф 4 mm, showing
matrix rich circumference ........................................................................................ 124
Figure 5.7: Hoop pressure (p ) applied on the braid shell, and (b) displacements (in
o
mm) encountered by rods due to applied hoop pressure .......................................... 126
Figure 5.8: Schematic representation of boundary conditions on the multi-scale model
in case of: (a) torsion, (b) three-point flexure, and (c) four-point flexure tests. ...... 128
Figure 5.9: Experimental and FE behaviour of hybrid composite wires under torsion
.................................................................................................................................. 131
Figure 5.10: Stress (von Misses in Nmm-2) distribution in multiscale model for 45°
braid with diamond braid topology at 3°/m twist: (a) without hoop pressure, and (b)
with hoop pressure. Note: SNEG (fraction = -1) implies stresses at face of shell in
contact the rods. ....................................................................................................... 133
Figure 5.11: Experimental and FE behaviour of hybrid composite wires for 3 point
flexural test ............................................................................................................... 135
Figure 5.12: Stress (von Misses in Nmm-2) distribution in multiscale model for 45°
braid with diamond braid topology at a mid-span deflection of 2.5 mm, in a 3 point
flexural set-up, (a) without hoop pressure and (b) with hoop pressure. Note: SNEG
(fraction = -1) implies stresses at face of shell in contact the rod ............................ 139
Figure 5.13: Experimental and FE behaviour of hybrid composite wires for 4 point
flexural test ............................................................................................................... 142
Figure 5.14: Stress (von Misses in Nmm-2) distribution in multiscale model for 45°
braid with diamond braid at a mid-span deflection of ~2.5 mm, in a 4 point flexural
set-up: (a) without hoop pressure, and (b) with hoop pressure. Note: SNEG (fraction
= -1) implies stresses at face of shell in contact the rods. ........................................ 145
Figure 6.1: Effect of coefficient of friction in hybrid composite wires using multiscale
model ........................................................................................................................ 148
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