A Contact Based Method for 3D Delamination Analysis of Composites Subjected to Impact Loading
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By: Sohail Forouzan-sepehr
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Supervisor: Dr S Mohammadi
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Major: Structural Engineering
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Viva Date: 26 September 2001
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Full Text: see Full Text (
Farsi)
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References: see References (
English) -
Research Report: see Report (
Farsi,
1034KB) -
Contents: see Contents (
English)
Abstract
Nowadays
composite materials are widely used in manufacturing of aircrafts, helicopters,
cars, satellite systems, etc. especially because of their lightness, high
strength-to-weight ratio, good damping characteristics, and high fatigue
strength. Therefore, having aircrafts larger than the Boeing 747 and faster than
the Concorde are not only possible but also a reality.
Recent
studies show that “delamination” and “matrix cracking” are the most
dominant causes of damage in composites subjected to impact loading.
Delamination highly increases the buckling risk and the local transverse impacts
by adjacent plies increase stress concentration in the cracks corners.
Therefore, the important role of the phenomena in reduction of bearing capacity
and performance of structure necessitate an accurate analysis of initiation and
propagation of interlaminar cracks and behaviour of the structure after
cracking.
The
aim of this study is to develop a reliable numerical method for 3D delamination
modelling based on the principles of plasticity, contact mechanics and fracture
mechanics. To do this, each ply or a group of similar plies is modelled with 3D
solid elements. Outside the region that cracking risk exists, coarser solid or
shell elements are used to reduce the analysis time. Special numerical methods
are employed for connecting the two systems and maintaining the compatibility
conditions at transition interfaces.
A contact based methodology is employed for modelling and controlling of plies bonding/debonding. The interlaminar behaviour in post delamination phase, such as slipping and crack faces interactions, is also considered by contact mechanics mechanisms. Employing an algorithm based on 3D contact mechanics in delamination analysis of composites is a novel technique and a more accurate and reliable analysis of this complex behaviour is expected to be obtained. In addition to 3D contact models, 3D anisotropic material models with strain softening behaviour are also developed and implemented to investigate 3D interlaminar crack propagation.
Contents
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Chapter 1: Introduction
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Chapter 2: Elasto-plastic constitutive laws for composite laminates
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Chapter 3: Interlaminar behaviour models of composites
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Chapter 4: Computational analysis method
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Chapter 5: Numerical studies
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Chapter 6: Conclusions
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References
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