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 Materials Overview Composite Structures Modeling: General FEA Workflow Analysis of Composites with ANSYS Mechanical APDL ANSYS Mechanical APDL: Composite Example ANSYS Mechanical APDL Limitations ANSYS Composites PrepPost: Introducing the ACP
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 anisotropy of the composite.
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
High stiffness-to-mass ratio Corrosion resistant Adjustable thermal expansion properties Exceptional formability 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) ANSYS DesignModeler Third-Party CAD Software
Model Solution
Post-Processing
Element Type Selection
(beam, solid, shell)
Results Viewing
(stresses, strains, interlaminar shear stresses, safety margins, etc.)
Mesh, Loads, BC Layup Definition
(thickness, angle, fiber material, integration points) ANSYS Mechanical APDL ANSYS WB Mechanical
ANSYS Structural Solvers
ANSYS APDL ANSYS Workbench
ANSYS Comp PrepPost
ANSYS Comp PrepPost
Failure Criteria Definition
(max strains, max stresses)
Analysis of Composites with ANSYS Mechanical APDL
At the global level (laminate)
- Overall deflection - Critical buckling loads - Natural frequencies and mode shapes
At the ply level
- 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
A composite lay-up is defined by inputting
Layer thickness Material ID (contains predefined 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
A composite lay-up is defined by inputting
Coefficients of the stiffness matrices [A] [B] [D] are computed outside of ANSYS Mech APDL and input into the Shell Section
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
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
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
Stringer Web
Stringer Flange
Fixed Support
Skin
Model 1: SOLSH190
ANSYS 8-node Layered Solid-Shell
Model 2: SOLID186
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
ANSYS 8-node Layered Solid-Shell
Model 2: SOLID186
ANSYS 20-node Layered Solid
ANSYS Mechanical APDL: Composite Example
Vertical skin displacement versus load
Both elements predict the buckling behavior well
Value Vertical Disp (mm)
0.00E+00
-1.00E+00
Primary skin buckling (~20 kN) Secondary skin buckling (~30 kN)
SOLID186 SOLSH190
However SOLSH190 captures postbuckling behavior SOLID186 results in solution divergence after an applied load of 135 kN
-2.00E+00
-3.00E+00
-4.00E+00
Buckle crosses stringer web (~135 kN)
-5.00E+00
-6.00E+00
-7.00E+00 0.00E+00 2.00E+04 4.00E+04 6.00E+04 8.00E+04 1.00E+05 1.20E+05 1.40E+05 1.60E+05
Applied Load (kN) Time
ANSYS Mechanical APDL Limitations
The definition of layers can be very time-consuming Complex geometries may hinder layer definitions Numerous local coordinate systems required for fiber orientations Limited failure theories and the inability to combine different criteria Difficulty with model draping or woven fabric composites 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 Provides seamless integration with ANSYS Workbench Mechanical and Mechanical APDL ANSYS Structural solvers are used to compute solution Efficient definition of materials, orientations, plies and stacking sequences 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 4) Solution is computed using the ANSYS solvers 5) Model results are imported into ACP for post-processing
Python Scripting Interface
ACP: Material Definitions
Specify Layer Properties
Model Tree
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
Model Tree
Defines a sequence of layers with different relative angles 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
Model Tree
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 Overlay text plot indicates critical failure mode, critical layers and critical load case 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 Through-thickness failure for shells Combination of failure criteria Ability to create user-defined criteria
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 ANSYS composite material modeling and post-processing limitations are overcome by the ANSYS Composite PrepPost (ACP) 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 ACP utilizes the ANSYS robust solvers to compute its base solution! ANSYS/ACP seamless integration will continue to progress in time!
