Durability, Damage Tolerance, and Life Prediction of Composite Materials

1
Durability, Damage Tolerance, and Life Prediction
of Composite Materials

• Scott Case
• Materials Response Group
• Virginia Tech
• Blacksburg, VA 24061-0219

2
Outline

• Example applications
• Flexible composite pipe
• Composite combustor liner (CMC)
• High-strain level bending of compositecylinder

3
Necessity for life prediction (or Why go to all
this trouble?)

• To certify structures for service
• Lack of life prediction techniques is currently
  viewed as the single biggest limitation to the
  use of composite in civil infrastructure
• To reduce the need for experimental testing
• To design new components or structures (what if
  studies)
• To warranty existing or new products

4
Example Applications

• Flexible composite pipe
• Combustor liner
• High-strain bending of composite cylinder

5
Use of flexible pipe in offshore oil industry
(Wellstream Inc.)

• Advantages of Polymer Composite material in
  flexible pipes
• 30 weight reduction - greater depths, lower deck
  loads
• Corrosion resistance - longer life, more fluid
  options

6
Typical loading environment

• Mechanical loads
• Tensile loads due to hanging weight
• Cyclic Bending loads due to wave-motion
• Positive and negative internal pressures
• Environmental loads
• Exposure to elevated temperatures
• Exposure to aggressive chemicals

7
Material

• Carbon Fiber/Polyphenylene Sulfide (PPS)
• Manufactured by Baycomp, Ontario Canada

8
Prediction of combined rupture and fatigue on
coupon level

• Characterize fatigue effect with room temperature
  fatigue tests
• Characterize elevated temperature effect with
  tensile rupture tests at temperature
• Combine effects using analysis and compare to
  experimental results

9
Characterize fatigue effect

• Fatigue Tests at 25C
• R 0.1
• f 10 Hz
• Fit data with S-N Curve

10
Characterize temperature effect

• Tensile rupture tests at 90 C
• Fit data with Kachanov-type curve

11
Predict of elevated temperature fatigue behavior

• Fatigue behavior accurately predicted at 90C, R
  0.1
• Validates the life prediction technique for this
  case

12
Model validation

• Full-scale tests will be run on a production
  prototype pipe at Wellstream.
• Combined tension, cyclic bending and internal
  pressure tests
• These tests will be used to validate and identify
  discrepancies in the model.

13
Example applications

• Flexible composite pipe
• Combustor liner
• High-strain bending of composite cylinder

14
Implementation CCLife program

• Begin with matrix stiffness reduction as a
  function of time and stress level
• Use a simple stress model (2-D, laminate level)
  to calculate failure function as a function of
  time, stress, and temperature
• Fit stress rupture data at 1800 F
• Shift fit to match rupture data from 925 F to
  2000 F
• Use incremental approach previously presented to
  sum influence of changing stresses (rupture
  influence)
• Adaptively refine increments until residual
  strength converges to some prescribed tolerance
• Account for cyclical loading by counting
  reversals and reducing remaining strength

15
Stress Rupture Data for Nicalon/E-SiC 2-D Woven
Composite 0/902s
16
Stress Rupture Data for Nicalon/E-SiC 2-D Woven
Composite 0/902s
17
Fatigue Data for Nicalon/E-SiC 2-D Woven
Composite 0/902s
18
Residual Strength Data for Nicalon/E-SiC 2-D
Woven Composite 0/902s (R-1, sinusoidal
loading)
19
Validation Mission loading profile
20
Validation results Mission loading profile
21
All results for Nicalon/E-SiC 2-D Woven
Composite 0/902s
22
Application to gas turbine engine combustor liner
23
Example applications

• Flexible composite pipe
• Combustor liner
• High-strain bending of composite cylinder

24
High-strain bending of Composite Cylinders

• Examine damage in cylinder as a function of load
  cycles
• Model lifetime as a function of applied stress
  (bending moment level) for different cylinder
  lay-ups
• Compare to qualification test data

25
Modeling results
First design
26
Modeling results
Second design
27
Modeling results
Third design
28
Conclusions

• A life prediction method for composites based
  upon remaining strength has been developed. The
  general approach is
• Conduct characterization tests and model behavior
  (under a single condition)
• Combine effects using life prediction analysis
• Validate life prediction using coupon level tests
• Apply validated analysis to a composite structure
• Validate structural analysis with limited testing
• Three example applications were considered
• Flexible composite pipe
• Combustor liner
• High-strain bending of composite cylinder

29
Ongoing/Future work

• Refine analysis to eliminate discrepancies
  between model/experiments
• Incorporate with finite element analysis to
  better model progressive failure as well as
  statistical strength distributions
• Develop analysis for out-of-plane failures

30
Sponsors of durability activities

• NASA Langley - life prediction for HSR (HSCT)
• Pratt and Whitney - high-T PMCs
• Wellstream - life prediction for flexible pipes
• Goodyear - truck tire durability
• McDermott Technologies - hot gas filters radiant
  burners
• Martin Marietta - CFCCs, time dependence
• Taylor Made Golf - composite golf shafts
• Boise Cascade - building product (using recylced
  materials)
• Owens Corning - shingles, pipe, tension members
• Strongwell - infrastructure applications (bridge
  and bridge deck)
• Federal Highway Administration - bridge and
  bridge deck
• National Science Foundation - durability of
  composites for infrastructure applications
• Schlumberger Technology - performance of
  high-temperature polymer composites in down-hole
  environments