SIMULATION DRIVEN DEVELOPMENT OF COMPOSITE STRUCTURES

Mikael Lauth

Senior Engineering Analyst, FEM

EDR & Medeso AB

2012-06-07

ANSYS Composite Prepost

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Efficient pre- and postprocessor for analysis of structures made of composite materials

Summary

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• Dedicated to allow for easy and efficient definition and modification of layered-composite structures as well as their specific post-processing

• Dedicated to provide leading-edge technology in pre- and post processing of layered composite structures

• Integrates with Mechanical Simulation as well as with Mechanical APDL

• Provides failure assessment as well as manufacturing information such as draping and plybooks.

Composites

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• Composite materials are made of at least two distinct materials with different material parameters for each phase

• Fiber reinforced composites (FRC) are composites where one material component (fiber) is used as a reinforcing material for the matrix

• Composites have a wide range of usage: sports, civil engineering, automotive & aerospace industry, shipbuilding, cables, consumer goods…

Basics

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Lamina- A composite material in sheet form

usually referred to as a layer or ply. The

material properties of a layer is usually

determined through an equivalent

homogenization (smearing) process.

Laminate- A stack of lamina joined

together in arbitrary directions,

referred to as a composite lay-up.

Matrix- A homogeneous base

material that forms the bulk of a

composite material layer.

Fibers- Bonded or embedded

reinforcing fibers that are

usually responsible for the

anisotropy of the composite.

L

T

Basics

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[90o / + / - / 0o] laminate

angle-ply laminate ±

cross-ply laminate = 0o / 90o

layer 4

4 = 0o

layer 1

1 = 90o

layer 2

2 = +

layer 3

3 = -

laminate

lamina

laminating

• wet-in-wet

- hand-lay-up

- sprayed-lay-up

• filament winding

• pultrusion

• resin transfer

molding

stacking sequence

Tools neded for analysis

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• An accurate representation of the structure in its environment: geometry, mesh, loads & boundary conditions

• An accurate representation of the composites : material behavior, ply definitions, orientations of the fibers…

• A numerically accurate solver

• A wide array of tools to investigate and understand the results and estimate the risks of failure

• Links to the manufacturing process (draping, plybooks) • All of this in a user-friendly environment!

ANSYS ACP

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The ANSYS Composite Prep/Post Advantage

Model representation

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• User of the ANSYS Composite Prep/ Post benefit from all the advantages of the ANSYS solutions:

• Direct CAD imports from all major CAD products

• Import of standard geometry formats (STEP, Parasolid…)

• Geometry cleaning

• Best-in class meshing capabilities for surface and solid models – with linear or quadratic elements

Model representation

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• Meshing information as well as loads and boundary conditions are transferred to ANSYS Composite PrepPost

Laminate modelling

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• A hierarchical data description of materials, stackups and laminates

Base information: Engineering data and material limits

Fabrics

Laminates

Stackups

Add thickness, pricing and draping information

Stack fabrics, add pricing and draping information

Define final laminate product

Definition of fiber direction

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• A key element of the definition of composite materials is the proper orientation of the fibers

• ANSYS Composite PrepPost uses a concept of oriented element-sets: • user can define material application

direction and material 0°direction

• One or several coordinate systems assigned to an oriented element-set

• no need for ply-subdivision

• Cartesian, cylindrical and spherical systems are supported

Definition of fiber direction

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• ANSYS Composite PrepPost uses a concept of oriented element-sets: • user can use lines or edged of the

geometry to specify fiber direction

• no need for ply-subdivision

• Cartesian, cylindrical and spherical systems are supported

Defining laminate areas

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• Laminates and associated orientations are defined on zones (element groups)

• Zones can be applied a pre- defined laminate

• Additional Laminates can be constructed by progressive stacking on zones

• Support for layer drop-off

Visualization of stacking

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• Stacking sequences and composite thicknesses can be displayed on arbitrary sections or on the entire model

Creating solid model based on shell model

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• Easy generation of solid model based on shell model (suitable for thick laminate analysis)

Shell model Extruded solid Snap to geometry

Computing the solution

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• The ANSYS Composite Prep/Post uses the ANSYS Mechanical solutions to compute the base solution of the model.

• All advantages of our core solutions are therefore available:

• Support of the latest element generation: linear and quadratic shells, linear and quadratic solids

• Layered element formulation

• Isotropic, orthotropic and anisotropic material models

• Fast and accurate solver

• Multiple time steps support

General postprocessing

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• Basic quantities like displacement, stress and strain.

• Arbitrarily configurable envelope contour failure plot

• Overlay Text-plots for easy identification of the relevant failure-modes and critical layer

• Sensor to calculate mass, area etc. for complete model or selected areas or group of elements.

• Generate superposition load cases based on initial load cases

Failure analysis

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• ANSYS Composite PrepPost provides a unique set of failure criteria to analyze the product: • From simple criteria (max stress) to state-

of-the art analysis (Puck, Hashin, Cuntze) • Interlaminar shear, normal stresses for shells • Through thickness failure for shells • Combination of failure criteria provides

failure envelope • 3D implementation of main criteria

(Tsai-Hill, Hashin, Puck etc.) • Ability to create user-defined criteria

Failure analysis

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• Results can be displayed as: • Most critical failure criteria

• Critical layer

• Reserve, inversed reserve factors and safety margin (based on stress limits)

• Standard results (stresses….) per layer

• Sampling elements

Draping & flatwrap

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• ANSYS Composite PrepPost provides draping functionality to analyze for drapability as well as for calculation of the fiber-angle correction

• Further ANSYS Composite PrepPost can also provide the flat-wrap of plies with their distortion

• Flatwrap boundaries export to STEP or IGES format

Flat-wrap

Draping

Plybook generation

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• A set of plies or all plies are selected for ply-book generation.

Additional capabilities

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• Python scripting capabilities provide full automation for the setup of the composite models as well as reusing data generated previously.

• ANSYS Composite PrepPost can update the model definition upon design changes without the need to redefine the entire model through a simple update of the input mesh.

Development process

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• ANSYS Composite Prepost is the high end tool in calculating composite structures and is suited to study lay ups with hundreds of layers

• Without engaging ANSYS Composite Prepost it is possible to set up layered section in Workbench Simulation to perform concept studies to find out: • Overall thickness • Major fiber orientation for individual layers • Material selection

Development process

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• In the example shown of a flat plate, simply supported and subject to an offset load at half length.

• The lay up is a sandwich construction with a core and 8 layers of glass fiber

• The governing output is total deflection • How does the fiber angles closest to the core influence the deflection?

Development process

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• ANSYS WorkBench Environment can with a few mouse clicks set up a sensitivity study (what if study) to investigate the variation of the output parameter due to a variation of an input parameter.

Development process

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• Next step is to go further using DesignExplorer that is a tool for performing: • Design of Experiments (DOE) studies on multiple input parameters

• Goal Driven Optimization to find the best design proposal

• Design for Six Sigma to account for scatter in input data and obtain a probability of how well the result fulfills the design requirements

• Get knowledge of how much each input parameter influence the output parameter. Which parameters are important and which who have less influence on the output parameters.

ESAComp

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FE-export/import

• ESAComp analyses can be used with the design tools for the preliminary design of laminated structures.

• Laminate lay-ups and the related properties specified in ESAComp can be exported into FE software using the FE export interface.

• After FE analysis, designers can import results to ESAComp using the FE import interface. This allows laminate level post processing and further improvement of the structure.

Analysis Tools

• Fiber/matrix micromechanics • Plies and laminates • Plates and stiffened panels • Beams and columns • Bonded joints and mechanical joints

The End

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END OF PRESENTATION Thank you for listening