Title: Durability of Polymer Matrix Composites for Infrastructure: The Role of the Interphase
1Durability of Polymer Matrix Compositesfor
Infrastructure The Role of the Interphase
K. N. E. Verghese
Advisor Dr. J. J. Lesko
Materials Engineering and Science
Program Virginia Tech
January 19th 1999
2Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Acknowledgements
3What is a Sizing?
A thin film applied to the surface of the carbon
before impregnation with the matrix material.
Phenoxy Particulate Sized
K-90 PVP Sized
4Why do Sizings Affect Properties?
- Processability-
- Sizings protect the brittle carbon fiber
- Sizings affect the wettability of the carbon
fiber - The Interphase (0-1 ?m) - Causes changes in
damage initiation and propagation. - Interdiffusion results in a concentration profile
or a mechanical property profile. - Changes in stochiometry of the matrix reactants.
5Why do Sizings Affect Properties?
- Matrix Plasticization (0-1 ?m) - An Interphase
with no gradients. - Results from a sizing that has diffused to such
an extent that no gradients exist. - Fiber/Matrix Adhesion (0-100 nm) - Causes changes
in interfacial properties like shear strength. - Results from a sizing that is physically or
chemically bonded to the fiber while interacting
strongly with the matrix.
6Influence of the Interface in Fiber Reinforced
Composites
Interfacial Shear Strength (ISS) (ksi/MPa)
Interfacial Failure Mechanism
Fiber Tensile Strength (ksi/MPa)
Transverse Tensile Strength (MPa)
Fiber Tensile Modulus (ksi/GPa)
Material
AU-4
34K/234.4
520/3585
5.4/37.2
Friction
18
AS-4
34K/234.4
520/3585
9.9/68.3
Interfacial
34.2
AS-4C
34K/234.4
520/3585
11.8/81.4
Matrix
41.2
Epon 828/ m-PDA Matrix
525/3.6
13/89.6
-----
-----
-----
Ref M. S. Makhukar and L. T. Drzal, Proc. Fifth
Tech. Conf. of the American Society for
Composites, 1990, 849 - 858.
7Influence of the Interface in Fiber Reinforced
Composites Continued.
Ref M. S. Makhukar and L. T. Drzal, Proc. Fifth
Tech. Conf. of the American Society for
Composites, 1990, 849 - 858. M. S.
Makhukar and L. T. Drzal, JCM Vol. 25 1991,
pp.932-957 M. S. Makhukar and L. T.
Drzal, JCM Vol. 25 1991, pp.958-991 M. S.
Makhukar and L. T. Drzal, JCM Vol. 26 1992,
pp.936-968
8Interphase and Interface Formation
- The sizing life cycle must be tracked to
fundamentally understand and predict interphase
and interface formation.
Fiber Preform
9Structure - Property Effects of Cross-link Density
Tear strength, fatigue life toughness
Static Modulus
Hardness
Tensile Strength
Property
Hysteresis. Permanent Set, friction coefficient
Cross-link density
10Interphase Micromechanics
Broken Fiber
Tensile Load
11The Approach
12Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
13Vinyl ester Resins
140-150C
styrene
benzoyl peroxide
The distance between crosslink junctions is one
factor controlling toughness. Higher Mc leads to
tougher materials.
14Fracture Toughness for Resin
Fracture toughness ---K1c (MPa-m.5)
ASTM D5045-91
Molecular weights are from proton NMR.
Courtesy Ellen Burts and Dr. H. Li
15Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
16Sizing Materials
- Poly(vinylpyrrolidone)
- (Brittle Thermoplastic)
- tensile strength for K90 62 MPa
- strain to failure 0.9
- Tg 180C (DSC)
- Polyhydroxyether
- (Tough Thermoplastic ?)
Mn 19k Tg? 97?C
tensile strength 55 MPa strain to failure
40-100 Tg 97C (DSC)
17Fully Reversed Fatigue Test Results of Cross-ply
Laminates
50
Run-out
40
Applied Stress (ksi)
30
Phenoxy Sizing
20
PVP-k17 Sizing
fatigue limit for Unsized
10
100
1,000
10,000
100,000
10,000,00
10,000,000
Number of Cycles
18Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
19Poly(hydroxyether) Sizing Materials
Unmodified Poly(hydroxyether)
OH
HO
C
O
CH
O
C
OH
x
Modified Poly(hydroxyether)
OH
HO
C
O
CH
O
C
OH
COOH
x
Poly(hydroxyether ethanolamine)
OH
OH
HO
C
O
CH
N
CH
O
C
OH
OH
x
20Preparation of sizing/matrix bilayers
Fiber in Matrix
Fiber
Cross section cut and microtomed (room temp. or
cryo)
21Tapping mode (phase) images of bilayer
cross-sections
a) Carboxy modified poly(hydroxyether) sizing and
Vinyl ester
b) Poly(hydroxyether ethanolamine) sizing and
Vinyl ester
22Nano-indentation
Courtesy Dr. M. A. F. Robertson
23Indentation profile across a carboxy functional
poly(hydroxyether)/vinyl ester cross section
140
Plastic Deformation
Elastic Deformation
130
Carboxy functional
Polyhydroxyether
120
110
Vinyl Ester
Depth (nm)
100
Vinyl Ester
10
0
-30
-20
-10
0
10
20
30
m
m)
Distance Relative to Interface (
24Indentation profile across a poly(hydroxyether
ethanolamine)/vinyl ester cross section
140
Plastic Deformation
Elastic Deformation
130
Polyhydroxyether ethanolamine
120
110
Vinyl Ester
Depth (nm)
100
10
Vinyl Ester
Polyhydroxyether ethanolamine
0
-30
-20
-10
0
10
20
30
Distance Relative to Interface (
m
m)
25Interfacial Shear StrengthsMicrodebond Test
Materials Fiber AS-4 Matrix 700 g/mol vinyl
ester with 30 wt. styrene cured with 1.1 wt.
Benzoyl peroxide, 130C/20 min.,N2
IFSS (MPa)
Sizing
None
288
Poly(hydroxyether)
43.68.7
Carboxylic acid modified poly(hydroxyether) MPE
52.64.7
Poly(hydroxyether ethanolamine) PHEA
22
Poly(vinylpyrrolidone) PVP
33.86.5
Phosphine oxide modified polyester urethane
56.77.5
Courtesy I. C. Kim and Dr. T. H. Yoon, Korea
26R-1 Fatigue Response at 10Hz on Notched Specimens
Poly(hydroxyether ethanolamine) Sized Composite
Compression Strength -48.6 ksi Modified
poly(hydroxyether) Sized Composite Compression
Strength -54.3 ksi
50
Modified Poly(hydroxyether) Sizing
40
Poly(hydroxyether ethanolamine Sizing
Run Out for modified poly(hydroxyether)
30
Applied Stress (ksi)
Run Out for poly(hydroxyether ethanolamine)
Run Out for Unsized
20
10
100
1000
10000
100000
1000000
10000000
Number of Cycles
27Dynamic Modulus Curves for Modified
Polyhydroxyether Sized Composites
28Residual Strength Test Levels for MPE Sized
Composites
29Residual Strength Curves on MPE Sized Composites
1.2
_at_ 37 ksi or 0.67
1
_at_ 34 ksi or 0.6
_at_ 31 ksi or 0.56
0.8
Normalized Stress
0.6
3 specimens for
2 specimens for
2 specimens for
0.4
each level
each level
each level
0.2
0
100
1000
10000
100000
1000000
Number of Cycles
30The MRLife Philosphy
31Preliminary Fatigue Performance Predictions
(MRLife)
50
Run Out
40
Applied Stress (ksi)
30
20
h Coefficient related to the bonding condition
of the fiber in Xu and Reifsniders
micro-mechanical compression model. 1lt hlt2
for the debonded and well bonded conditions
respectively
10
100
1000
10000
100000
1000000
10000000
Cycles to Failure (Log N)
32Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
33Recent Work
50
Run Out
40
Applied Stress (ksi)
30
20
LMWVE stands for low molecular weight vinyl
ester HMWVE stands for high molecular weight
vinyl ester
10
100
1000
10000
100000
1000000
10000000
Number of Cycles (log cycles)
34Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
35Schematic of Pultrusion Line
36Tensile Strength of Pultruded Composites
37Longitudinal Flexure Strength Strength
38Short Beam Shear Strength of Pultruded
39Tensile Strength Comparison between Model and
Experimental Data
40Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
41Cooperativity Model
- Intermolecular interactions and constraints
- Segments move in a cooperative motion
- Degree of cooperativity - temperature dependence
of log(aT)
z 6
log(aT)
Glassy State
Tg
Tg/T
Relaxation Phenomena in Polymers Shiro Matsuoka
42Concept of Cooperativity
20
15
increasing n
10
- equilibrium
- bulk polymers
T
5
log a
0
-5
-10
-0.05
0.00
0.05
0.10
0.15
(T-T
)/T
g
g
D. J. Plazek and K. L. Ngai, Macromolecules,
24, 1222 (1991).
43Vinyl Ester Resins
Vinyl Ester
Styrene
Calculated
Measured
T
T
DSC
g
g
D
C
T
p
Oligomer Weight
Content
M
M
Onset
End
g
c
c
(J/gC)
(g/mol)
()
(g/mol)
(g/mol)
(DSC,C)
(DSC,C)
(C)
700
20
292
300
136
164
152
0.269
700
35
359
569
124
145
136
0.244
1200
20
417
812
115
133
125
0.322
1200
35
513
969
110
126
118
0.298
44Dynamic Loss Modulus
Vinyl Ester (Mn 1200g/mol, 20 Styrene)
45Fragility (cooperativity) plot for vinyl ester
resins
20 700g/mol
William-Landel- Ferry equation
35 700g/mol
20 1200g/mol
35 1200g/mol
)
T
log(a
n d(logaT)/d(Tg/T)Tg
fragility (cooperativity)
Tg / T
46Cooperativity versus molecular weight between
crosslinks
94
1200, 20
92
700, 20
90
88
86
84
n, fragility
82
80
78
1200, 35
76
700, 35
74
72
0.002
0.003
0.004
1/Mc (mol/gram)
47Fracture toughness versus normalized domain size
48Master Curve - Matrix
Tg 137C
log E (MPa)
log waT
log w
107C - 164C, 3 C steps, second heat
49Master Curve - Composite
Tg 123C
log E (MPa)
log waT
log w
93C - 219C, 3 C steps, Phenoxy sizing, second
heat
50DMA - damping of composites
G PVP Phenoxy
1 Hz, second heat
51Cooperativity plot for composites
matrix G PVP Phenoxy
increasing n
52Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
53Moisture Uptake Plots
Specimen Dimensions for Study 4cm x 0.764cm x
0.254 cm
54Diffusion Theory Ficks Law
Rigorous Solution
Semi-infinite Case
D is evaluated from the initial slope of a graph
of moisture content as a function of t1/2
55Effects of Exposure Temperature on Diffusion
Coefficient for Derakane 441-400
All aging performed under isothermal conditions
and complete immersion in water.
-14
2.03E-07
-15
-16
5.37E-08
2.5E-08
ln D (cm2/sec)
-17
1.18E-08
-18
-19
-20
0.0026
0.0028
0.003
0.0032
0.0034
1/Temperature (1/K)
56Saturation Moisture Content Theory
Modified Henrys Law
where xw is the weight fraction of water in the
polymer and VP is the vapor pressure at the
test temperature of the bulk liquid phase and is
computed using the Claussius-Claypron equation
which is as follows
where p, ?Hsub, R, T and T are the vapor
pressure at the triple point, heat of
sublimation, gas constant, temperature and
triple point temperature respectively.
57Effects of Exposure Temperature on Henrys
Constant for Derakane 441-400
58Fourier Tranform Infrared (FTIR)Spectra of
Derakane 441-400
59Reverse Thermal Effect (RTE)
60Activation Energy for the RTE Process
D 4.76E-10 exp(2.28E04/RT)
Activation Energy 5.7 KCal/mole Theoretical
Hydrogen Bond Energy 5 KCal/mole
0.12
-11
0.1
-12
0.08
Moisture Content ()
-13
0.06
Hydrogen Bonding!
0.04
-14
0.02
-15
0
0.0028
0.003
0.0032
0.0034
0.0036
14
0
2
4
6
8
10
12
1/Temperature (1/K)
Time (hours1/2)
61Chemical Structure Comparisons
CH3-GMA (Model Resin System)
Reference H. K. Shobha, M. Sankarapandian, A. R.
Shultz, and J. E. McGrath, Macromol. Symp. 111,
73-83 (1996)
62FTIR of Model Resin System
63RTE on Model Resin System
64Moisture Uptake in Unidirectional Composites
1.2
G'
Immersion in water bath at 62C
Low Spread Phenoxy
PVP K90
OCF Glass Fiber
1
0.8
Moisture Content ()
0.6
0.4
0.2
0
0
5
10
15
20
25
30
35
40
45
Time (hours
1/2
)
65Outline for Presentation
- Introduction What is a Sizing?
- Materials Used
- Results obtained thus far
- Mechanical properties of laminates
- study 1
- study 2
- study 3
- pultruded composites
- Thermo-mechanical experiments
- dynamic mechanical analysis of resin and
composites - Environmental Durability
- hygrothermal aging of resin and composites
- Proposed work for the future
- Acknowledgements
66Proposed Work
1) Focus on studying unidirectional composite
response
As Received Material
Saturate composites in water at 62C
Fatigue Tests on composites
Tg and cooperativity measurements
Quasistatic Tension Short Beam Shear Tests
Freeze-Thaw Tests
IITRI compression tests
Quasistatic Tension Short Beam Shear Tests
?45 laminate tensile tests
67Proposed work continued
2) Blend Properties
Study blends of 1) PVP K90/ vinyl ester 2)
Phenoxy/vinyl ester
Saturate composites in water at 62C
Tg and cooperativity measurements
- 3) Pultrude composites at Strongwell to study the
- effect of coating thickness (eg. Phenoxy)
- effect of sizing molecular weight (eg. PVP K90
vs. K30)
68Proposed work continued
3) Fatigue response of hygrothermal aged
cross-ply composites. 4) Incorporate the effect
of the interphase into MRLife. 5) Try and model
the interphase by using blend data in a code
written by Dr. Pagano and Dr. Tandon
69Acknowledgements
- Dr. R. Parnas and Dr. D. Hunston at NIST
- Dr. M. Puckett, The Dow Chemical Company
- Clint Smith, Strongwell Inc.
- Dr. Pagano, Wright Patterson Airforce Base
- Dr. H. Li
- Lu Shan, 1998 SURP student
- Chris Robertson, Chemical Engineering Dept.
- Rob Jensen, Chemistry Dept.
- Ellen Burts and Maggie Bump, Chemistry Dept.
- Norman Broyles, Chemical Engineering Dept.
- Mark Flynn