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Damage and Optimization Models for Analysis and Design of Discontinuous Fiber Composite Structures

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Current State of the Art in Design and Optimization of Discontinuous Fiber Composites ... and Mori-Tanaka frameworks (e.g. elastic-plastic, damage, creep) ... – PowerPoint PPT presentation

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Title: Damage and Optimization Models for Analysis and Design of Discontinuous Fiber Composite Structures


1
Damage and Optimization Models for Analysis and
Design of Discontinuous Fiber Composite Structures
  • Ba Nghiep Nguyen
  • Acknowledgements PNNLs Computational Science
    Engineering Initiative
  • Korolev Vladimir, Brian Tucker (contributors)

NSF/DOE/APC Workshop Future of Modeling in
Composites Molding Processes (Design
Optimization Session), June 9-10, 2004,
Arlington, Virginia
2
Damage and Optimization Models for Analysis and
Design of Discontinuous Fiber Composite
Structures
PNNL has developed
  • A multiscale mechanistic approach to damage
    based on
  • micromechanical and continuum damage mechanics
    descriptions
  • An optimization approach using the optimal
    control theory accounting for the composite
    microstructure
  • An experimental procedure for acquiring
    acoustic emission signals to identify damage

3
Damage and Optimization Models for Analysis and
Design of Discontinuous Fiber Composite
Structures
Optimal Control Theory Approach to Short-Fiber
Composites
Fiber volume fractions Fiber aspect ratios
Fiber orientation parameter
4
Current State of the Art in Design and
Optimization of Discontinuous Fiber Composites
  • Elastic analysis-based design
  • Micromechanical models rely on material database
    (fiber volume fraction, aspect ratio, orientation
    distribution, etc.) to predict effective
    properties
  • Process modeling to predict fiber orientation
  • Control of process and microstructural parameters
    to improve composite stiffness
  • Elastic finite element analysis of the as-formed
    composite structure
  • Nonlinear analysis based design
  • Phenomenological models rely on material database
    and testing of specimens
  • Nonlinear micromechanical models derived from the
    self-consistent and Mori-Tanaka frameworks (e.g.
    elastic-plastic, damage, creep)
  • PNNL damage models using a multiscale mechanistic
    approach
  • ORNL micromechanical models
  • Formal optimization methods
  • Only at the beginning
  • Duvaut et al. (2000). Optimization of Fiber
    Reinforced Composites, Composite Structures, 48,
    83-89
  • PNNL optimization model using the optimal control
    theory

5
Vision on Future Directions
  • Design optimization methods should be reliable
    to effectively assist processing manufacturing
    of composite components and parts
  • Development of new process and constitutive
    models accounting for the constituents
    characteristics and properties, and their
    interaction with each other
  • Interface between process modeling and structural
    modeling to create and design a composite part
    through simulations
  • Processing manufacturing can rely on efficient
    design optimization methods rather than on
    trial-and-error approaches
  • Reduce the number of experimental tests and trial
    moldings

Manufacturing
Structural modeling
Process modeling
6
Perceived Gaps
  • Where we are now
  • Micromechanical models predict elastic properties
    and some nonlinear responses
  • Process models provide qualitative predictions of
    fiber orientations in injection molding
  • Phenomenological constitutive models exist in
    commercial FE codes for structural analyses
  • Limited interface between process and structural
    modeling
  • Analysis and design are still based on intensive
    material database obtained through experiments
  • Initiation of multiscale mechanistic models based
    on micromechanics and continuum mechanics
  • Where we should be
  • Accurate micromechanical models accounting for
    concentrated fiber volume fractions
  • Accurate process models for short- and long-fiber
    thermoplastic injection molding
  • Constitutive physics-based models for predicting
    durability and time-dependent behavior
  • Interface between process and structural modeling
    for linear and nonlinear analyses
  • Optimization methods accounting for process,
    design and loading variables and constraints
  • Analysis and design should rely on reliable
    physics-based models to assist processing
    manufacturing

7
Research Thrusts
  • Micromechanics
  • Process micromechanics Effects of fiber content,
    length on the rheology and fiber orientation
  • Micromechanics of materials Homogenization
    accounts for interaction between constituents and
    defects
  • Continuum mechanics Need of constitutive models
    for
  • Fatigue
  • Time dependent behaviors (creep, relaxation,..)
  • Impact
  • Moisture
  • Optimization models accounting for nonlinear
    behaviors
  • Minimization of damage
  • Improvement of durability (fatigue, creep)
  • Multi-scale modeling
  • From a microstructural to a continuum model
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