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

StructuresStructures

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

StructuresStructures

Ba Nghiep Nguyen

Acknowledgements: PNNL’s 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

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

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

Acoustic emission techniques to identify damage

Model validation

Damage & failure analyses

- Fibers, matrix - Fiber/matrix interfaces - Microcracks

Continuum

Homogenization

Microscale

Composite representative volume element

Mesoscale

Macroscale

Composite structure

Constitutive relations Evolution laws Finite element analysis

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

PNNL has developed:

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Damage and Optimization Models for Analysis and Damage and Optimization Models for Analysis and

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

Design of Discontinuous Fiber Composite StructuresDesign of Discontinuous Fiber Composite Structures

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Optimal Control Theory Approach to Short-Fiber Composites

Fiber volume fractions Fiber aspect ratios Fiber orientation parameter

Optimization of fiber orientation distributionfor the plate under tensile loading. The orientationsare planar with density: e)(

λOptimizer

Using sequential linear programming Determines optimum

Finite Element Analysis Resolution of direct &

adjoint equations Stress/strain computation

Micromechanics Stiffness calculation Derivative of stiffness

Derivative Calculator Lagrange Functional Stationarity conditions

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Current State of the Art in Design and Optimization of Current State of the Art in Design and Optimization of Discontinuous Fiber CompositesDiscontinuous Fiber Composites

Current State of the Art in Design and Optimization of Current State of the Art in Design and Optimization of Discontinuous Fiber CompositesDiscontinuous 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

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Vision on Future DirectionsVision on Future DirectionsVision on Future DirectionsVision 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

Process modeling Structural modeling Manufacturing

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Perceived GapsPerceived GapsPerceived GapsPerceived 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

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Research ThrustsResearch ThrustsResearch ThrustsResearch 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 defectsContinuum 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