Analysis of Composite Structures using ANSYS 12.0 and the ANSYS Composites PrepPost (ACP): An Overview Jean Paul Kabche, Ph.D. Giovanni de Morais, M.Sc. Maira Vargas, M.Sc. Engineering Simulation Scientific Software (ESSS)
Presentation Outline •
Composite Ma Materials Ove Overview
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Comp Co mpos osit ite e St Stru ruct ctur ures es Mod Model elin ing: g: Gen Gener eral al FEA FEA Workfl orkflow ow
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Anal An alys ysis is of of Comp Compos osit ites es wi with th AN ANSY SYS S Mech Mechan anic ical al APDL APDL
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ANSY AN SYS S Mech Mechan anic ical al APDL APDL:: Comp Compos osit ite eE Exa xamp mple le
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ANSY AN SYS S Me Mech chan anic ical al APDL APDL Limi Limita tati tion ons s
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ANSY AN SYS S Com Compo posi site tes s Pre PrepP pPos ost: t: Intr Introd oduc ucin ing g the the AC ACP P
Composite Materials: What are they? Matrix: A homogenous base material that forms the bulk of a composite material layer. Fibers: Bonded or embedded reinforcing fibers that are usually responsible for the anisotro of the com osite. Transverse fiber direction
Longitudinal fiber direction
Lamina: A composite material in sheet form usually referred to as a layer or ply .
Laminate: A stack of lamina joined together in arbitrary directions, referred to as a composite lay-up .
Composite Materials: Why use them? •
Benefits of composites – – – – –
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High stiffness-to-mass ratio Corrosion resistant Adjustable thermal expansion properties Exce tional formabilit Outstanding durability
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Composite applications – – – –
Aerospace Automotive Sporting goods Many, many others…
Composite Structures Modeling: General FEA Workflow Pre-Processing Geometry Creation (lines, surfaces, volumes)
Model Solution
Post-Processing
ANSYS DesignModeler Third-Party CAD Software
Element Type Selection
esu s
ew ng
(stresses, strains, interlaminar shear stresses, safety margins, etc.)
(beam, solid, shell)
Mesh, Loads, BC Layup Definition
ANSYS Mechanical APDL
(thickness, angle, fiber material, integration points)
ANSYS WB Mechanical
ANSYS Structural Solvers
ANSYS APDL ANSYS Workbench
ANSYS Comp PrepPost
Failure Criteria Definition (max strains, max stresses)
ANSYS Comp PrepPost
Analysis of Composites with ANSYS Mechanical APDL • At the global level (laminate) - Overall deflection - Critical buckling loads - Natural frequencies and mode shapes
• - Interlaminar shear stresses
• At the matrix level - Stress distribution at matrix/fiber interfaces
• Failure of composites - Buckling of the structure (global level) - Delamination (ply level) - Fiber detachment (matrix level)
Analysis of Composites with ANSYS Mechanical APDL •
Defining Composite Lay-ups >> Regular Shell Section
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A composite lay-up is defined by inputting •
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Layer thickness defined layer-wise material properties) Orientation (fiber angle with respect to a pre-defined reference coordinate system) Integration Pts (through-thethickness integration points)
Analysis of Composites with ANSYS Mechanical APDL •
Defining Composite Lay-ups >> Pre-integrated Shell Section
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A composite lay-up is defined by inputting •
Coefficients of the stiffness computed outside of ANSYS Mech APDL and input into the Shell Section
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Recall that... • • •
[A] = membrane stiffnesses [B] = coupling stiffnesses [D] = bending stiffnesses
Analysis of Composites with ANSYS Mechanical APDL •
Element technology for composite modeling – 1D: BEAM188/ BEAM189 – 2D: SHELL181/ SHELL281/ SHELL208/ SHELL209 – 3D: Layered SOLID185/ Layered SOLID186/ SOLSH190
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Failure criteria: has a layer failed due to the applied loads? – Maximum Strain Failure Criterion: nine failure strains – Maximum Stress Failure Criterion: nine failure stresses – Tsai-Wu Failure Criterion: nine failure stresses and three additional coupling coefficients
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Failure by interface delamination – “Cohesive Zone Modeling” (CZM): specifies element separation laws
ANSYS Mechanical APDL: Composite Example • •
Modal Analysis/ Buckling Analysis of a Composite Stiffened Section Compare the performance of SOLSH190 and SOLID186 Compressive Load Strin er Web
Stringer Flange
Skin
Fixed Support
Model 1: SOLSH190
Model 2: SOLID186
ANSYS 8-node Layered Solid-Shell
ANSYS 20-node Layered Solid
ANSYS Mechanical APDL: Composite Example •
Results: Vertical Displacement (UZ) at 30 kN (first buckling load)
Secondary Skin Buckling
Buckling Load = 31.6 kN
Buckling Load = 30.6 kN
Model 1: SOLSH190
Model 2: SOLID186
ANSYS 8-node Layered Solid-Shell
ANSYS 20-node Layered Solid
ANSYS Mechanical APDL: Composite Example •
Vertical skin displacement versus load
• Both elements predict the buckling behavior well…
0.00E+00
Primary skin buckling (~20 kN)
-1.00E+00
However… • SOLSH190 captures postbuckling behavior • SOLID186 results in solution divergence after an applied load of 135 kN
SOLID186 SOLSH190
Secondary skin buckling (~30 kN)
)-2.00E+00 m m ( p-3.00E+00 e s i u l a D l V a-4.00E+00 c i t r e V-5.00E+00
Buckle crosses stringer web (~135 kN)
-6.00E+00
-7.00E+00 0.00E+00
2.00E+04
4.00E+04
6.00E+04
8.00E+04
1.00E+05
Applied Load (kN) Time
1.20E+05
1.40E+05
1.60E+05
ANSYS Mechanical APDL Limitations •
The definition of layers can be very time-consuming
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Complex geometries may hinder layer definitions
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Limited failure theories and the inability to combine different criteria
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Difficulty with model draping or woven fabric composites
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Limited post-processing capabilities
ANSYS Composites PrepPost: Introducing the ACP •
A new tool with advanced composites functionalities for pre- and postprocessing of layered composite structures
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Provides seamless integration with ANSYS Workbench Mechanical and Mechanical APDL
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ANSYS Structural solvers are used to compute solution
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Efficient definition of materials, orientations, plies and stacking sequences
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State-of-the-art failure criteria for composite structures
ACP: General Analysis Workflow 1) Mesh, loads and boundary conditions are defined in ANSYS Mechanical APDL or ANSYS WB Mechanical 2) ACP is launched from ANSYS WB Mechanical or Mechanical APDL for composite material pre-processing 3) ACP generates an APDL file Main Window Model Tree
Python Scripting Interface
4) Solution is computed using the ANSYS solvers 5) Model results are imported into ACP for post-processing
ACP: Material Definitions Specify Layer Properties
e r T l e d o M
• Basic engineering data used for finite element calculations • Engineering constants (E1, E2, E3, G12, …, etc.) • Failure criteria: strain limits, stress limits, Puck constants
ACP: Sub Laminate Definitions Specify Layup Configuration
• Defines a sequence of layers with different relative angles e r T l e d o M
• Each layer is assigned a set of material properties • Can be re-used in different areas of the structure
ACP: Local Coordinate Systems for Fiber Orientation Specify local systems for various regions of the model
e r T l e d o M
• Definition of Cartesian, cylindrical and spherical systems for fiber angle orientation definitions
ACP: Failure Analysis and Post-Processing •
Composite failure criteria is evaluated at all integration points of all layers of all elements requested
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Overla text lot indicates critical failure mode, critical layers and critical load case
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Definition of arbitrary failure criteria combinations – Max. strain and stresses, Tsai-Wu, TsaiHill, Hashin, LaRC – Core failure and face sheet wrinkling for sandwich structures
ACP: Failure Analysis and Post-Processing •
Failure criteria provided – Simple criteria (maximum stress) to state-of-the-art (Puck criterion) – Interlaminar shear and normal stresses for shells – – Combination of failure criteria – Ability to create user-defined criteria
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Results displayed as – Critical failure criteria – Critical layer – Safety margins, reserve and inversed reserve factors
Text plot highlighting critical failure mode, layers and load case
Composite Structure Analysis: Summary •
ANSYS Mechanical and Mechanical APDL are capable of analyzing composite structures using beam, shell and solid elements
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ANSYS’ composite material modeling and post-processing limitations are overcome b the ANSYS Com osite Pre Post ACP
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ACP provides advanced composite pre- and post-processing capabilities which include: material definitions, layups, stackups, failure criteria, identification of critical failure mode, layer and load conditions
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ACP utilizes the ANSYS’ robust solvers to compute its base solution!
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ANSYS/ACP seamless integration will continue to progress in time!
