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UBC Theses and Dissertations
Crack growth and damage modeling of fibre reinforced polymer composites McClennan, Scott Andrew
Abstract
Notched tensile strength and the development of damage in composite laminates are studied in this thesis through experimental, numerical and analytical methods to develop simple models for predicting notched strength using completely physical input parameters. A series of experimental tensile fracture tests using the Overheight Compact Tension (OCT) specimen geometry, established by (Kongshavn and Poursartip, 1999), were conducted to study the development of the characteristic damage zone. The material used in the tests was a quasi-isotropic carbon fibre/epoxy. The specimens were modified so that the notch root radius varied while maintaining a constant crack width to specimen section ratio. Specimens with notch root radii less than 16 mm display stable crack growth with little notch sensitivity. Specimens with larger notch root radii are unstable and display more notch sensitivity. For all specimens, the height of the damage zone converges to between 6 mm. and 7 mm. The transition from stable to unstable behaviour is explained using fracture mechanics equations and a transition radius can be determined from three material parameters; elastic modulus, specific strain energy and tensile strength. A simple bilinear cohesive zone model called the simple damage model (SDM) was developed as a material model in the ABAQUS finite element code to be used as a demonstrator for modeling techniques that can be applied to all strain-softening material models. In particular, the relationship between input parameters and the element width was studied. Using the same input parameters as the analytical model and a sufficiently refined mesh, the numerical model predicts the peak loads from the series of experimental OCT tests well. A transition from stable to unstable behaviour is predicted at the same radius as seen experimentally. A method of determining an appropriate element width to ensure an accurate prediction is presented. A modified version of the SDM called the adaptive simple damage model (ASDM) was also developed, which automatically scales the input strength to account for the effect of element width. This modification allows larger elements to be used while still obtaining an accurate solution, a useful feature if large structures are being modeled.
Item Metadata
Title |
Crack growth and damage modeling of fibre reinforced polymer composites
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2004
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Description |
Notched tensile strength and the development of damage in composite laminates are studied
in this thesis through experimental, numerical and analytical methods to develop simple models for predicting notched strength using completely physical input parameters. A series of experimental tensile fracture tests using the Overheight Compact Tension (OCT) specimen geometry, established by (Kongshavn and Poursartip, 1999), were conducted to study the development of the characteristic damage zone. The material used in the tests was a quasi-isotropic carbon fibre/epoxy. The specimens were modified so that the notch root radius varied while maintaining a constant crack width to specimen section ratio. Specimens
with notch root radii less than 16 mm display stable crack growth with little notch sensitivity. Specimens with larger notch root radii are unstable and display more notch sensitivity. For all specimens, the height of the damage zone converges to between 6 mm. and 7 mm. The transition from stable to unstable behaviour is explained using fracture mechanics equations and a transition radius can be determined from three material parameters; elastic modulus, specific strain energy and tensile strength.
A simple bilinear cohesive zone model called the simple damage model (SDM) was developed as a material model in the ABAQUS finite element code to be used as a demonstrator for modeling techniques that can be applied to all strain-softening material models. In particular, the relationship between input parameters and the element width was studied. Using the same input parameters as the analytical model and a sufficiently refined mesh, the numerical model predicts the peak loads from the series of experimental OCT tests well. A transition from stable to unstable behaviour is predicted at the same radius as seen
experimentally. A method of determining an appropriate element width to ensure an
accurate prediction is presented.
A modified version of the SDM called the adaptive simple damage model (ASDM) was also
developed, which automatically scales the input strength to account for the effect of element width. This modification allows larger elements to be used while still obtaining an accurate solution, a useful feature if large structures are being modeled.
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Extent |
14365672 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-11-25
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0078773
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2004-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.