composites analysis using nastran/patran by dr. faeq m. shaikh
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Composite AnalysisUsing NASTRAN / PATRAN
Dr. Faeq M. Shaikh
Seattle, Washington, USA
(Seattle is home of Boeing Jets)
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Composite AnalysisUsing NASTRAN / PATRAN
• Pre‐Requisites for Today’s Seminar
Basic understanding of Finite Element Analysis
Working Knowledge of Laminate Plate Theory
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Composite AnalysisUsing NASTRAN / PATRAN
• NASTRAN & PATRAN are products of McNeal Schwendler Corporation (MSC)
• PATRAN = Pre & Post Processor• NASTRAN (NASA Structural Analysis)= Solver
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Composite AnalysisUsing NASTRAN / PATRAN
PATRAN
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Modeling CapabilitiesLine (Bar) Elements:
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Modeling CapabilitiesLine (Beam) Elements:
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Modeling CapabilitiesSurface (Shell) Elements:
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Modeling CapabilitiesSurface (Shell) Elements:
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Modeling CapabilitiesSolid Elements:
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Results ‐ Deformation
Animate Deformation
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Results ‐ Deformation
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Composite AnalysisUsing NASTRAN / PATRAN
• Summary of PATRAN Results ‐ Stresses
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Composite AnalysisUsing NASTRAN / PATRAN
• Process of Finite Element Analysis:Set database units (British or Metric)Define or Import (from CAD tools) GeometryCreate finite element meshDefine materials (isotropic, orthotropic, anisotropic)Define laminate / sandwich materialsApply materials to element propertiesApply loads and boundary conditionsPerform analysis (Linear, Non‐Linear, Buckling, etc)Access ResultsCreate fringe and deformation plots
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Composite AnalysisUsing NASTRAN / PATRAN
• Shell (Plate) vs. Solid ElementsMesh Using Shell
Elements:• Can model bending.•Usually much smaller model size• Elements are created on a surface (area)• Limited thru‐thickness results
Mesh Using Solid Elements:
•Do not have bending capability•Much larger model size• Elements are created on a volume• Thru‐thickness result capabilities
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Composite AnalysisUsing NASTRAN / PATRAN
• Examples of Models with Shell & Solid Elements:
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Composite AnalysisUsing NASTRAN / PATRAN
• Composites can be modeled using both shell and solid elements. Choice depends on:Computing power (large vs. small models) What kind of results are required (2D vs. 3D state of stress in‐plane vs. thru‐thickness)Importance of interfaces (fitting attachments, etc.) IF
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Composite AnalysisUsing NASTRAN / PATRAN
• 2D vs. 3D State of Stress
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Composite AnalysisUsing NASTRAN / PATRAN
• Composites can also be modeled as a hybrid of shell and solid elements
Model facesheet as shell elements
Model facesheet as shell elements
Model core as solid elements
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Composite AnalysisUsing NASTRAN / PATRAN
• Materials – Isotropic:
3D Constitutive Relationship
Plane StressConstitutive Relationship
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Composite AnalysisUsing NASTRAN / PATRAN
• Materials – Orthotropic:MAT3 Orthotropic materialis defined for Solid elements.
MAT8 orthotropic materialis defined for shell elements.
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Composite AnalysisUsing NASTRAN / PATRAN
• Materials – Anisotropic:
The MAT2 is used to define 2D anisotropic constitutive stress-strain relationship using the anisotropic material matrix.
The MAT9 is used to define 3D orthotropic constitutive stress strain relation using the anisotropic material matrix.
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Composite AnalysisUsing NASTRAN / PATRAN
• Laminate Plate Theory – Overview
The laminate consists of perfectly bonded laminae.The bonds are infinitesimally thin and nonshear‐deformable; i.e., displacements are continuous across laminae boundaries so that no lamina can slip relative to another.Each of the lamina is in a state of plane stress.
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Composite AnalysisUsing NASTRAN / PATRAN
• Modeling composites:Laminated composites are a "stack" of laminae with different orientations
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Composite AnalysisUsing NASTRAN / PATRAN
• Modeling composites‐what do we need?Lamina properties (E, G, etc)OrientationThicknessStacking sequence
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Composite AnalysisUsing NASTRAN / PATRAN
• Modeling composites‐what do we need?Data RecoveryDisplacementsForcesPly StressesPly StrainsMargin of Safety / Failure Indices
FI < 1, the lamina is assumed safe.FI > 1, the lamina is assumed to have failed.
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Composite AnalysisUsing NASTRAN / PATRAN
• Failure Indices:Isotropic Materials: Strength is independent of orientation of body under loadLaminated Composites (orthotropic ): Strength is a function of body orientation relative to load.Minimum Allowables Required:
Tensile stress/strain in material 1 & 2 directionsCompressive stress/strain in material 1 & 2 directionsShear stress/strain in principal material direction.
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Composite AnalysisUsing NASTRAN / PATRAN
• Failure Theories in NASTRAN / PATRAN:
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Composite AnalysisUsing NASTRAN / PATRAN
• Start a project:
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Composite AnalysisUsing NASTRAN / PATRAN
• PATRANModeling Window
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Composite AnalysisUsing NASTRAN / PATRAN
• PATRANApplication Form
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Composite AnalysisUsing NASTRAN / PATRAN
Creating Geometry: 1
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Composite AnalysisUsing NASTRAN / PATRAN
• Creating Mesh: 1
2 3
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Composite AnalysisUsing NASTRAN / PATRAN
• Materials:
1
2
3
4Creating Uni‐Directional Tape(for 2D Shell Elms)
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Composite AnalysisUsing NASTRAN / PATRAN
• Materials:
1
2
3
4Creating Honeycomb Core(for 2D Shell Elms)
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Composite AnalysisUsing NASTRAN / PATRAN
• Materials:
1
2
3
4
Creating Honeycomb Core(for 2D Shell Elms)
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Composite AnalysisUsing NASTRAN / PATRAN
• Materials:
1
2
Laminate Constants(for 2D Shell Elms)
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Composite AnalysisUsing NASTRAN / PATRAN
• Element vs. Material Coordinate System:
For 2D shell elements, ECS from Node 1 to Node 2Element Forces come out in Element Coordinate Sys
MCS defines the 0 deg fiber directionPly Strains & Stresses come out in ply fiber directions / Material Coordinate System
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Composite AnalysisUsing NASTRAN / PATRAN
• Properties:
1
2
3
4
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Composite AnalysisUsing NASTRAN / PATRAN
• Geometry:
1. Create Points2. Create Surface
3. Create solid (for 3D analysis)
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Composite AnalysisUsing NASTRAN / PATRAN
• FEMs:
1. Create Nodes & Elements (2D)
2. Create solids (for 3D analysis)
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Composite AnalysisUsing NASTRAN / PATRAN
• Apply Loads: 1
2
3
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Composite AnalysisUsing NASTRAN / PATRAN
• Apply Boundary Conditions: 1
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4
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Composite AnalysisUsing NASTRAN / PATRAN
• Analyze:1
2
3
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Composite AnalysisUsing NASTRAN / PATRAN
• 3D Modeling:
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Composite AnalysisUsing NASTRAN / PATRAN
• 3D Modeling:
Facesheets modeled with 2D Shell Elements
Honeycomb Core modeled with 3D Solid Elements
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Composite AnalysisUsing NASTRAN / PATRAN
• 3D Anisotropic Material:
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Composite AnalysisUsing NASTRAN / PATRAN
• Results – Deformation plot:
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2
3
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Composite AnalysisUsing NASTRAN / PATRAN
• Ply‐1 (bottom) x‐direction strain fringe plot:
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2
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4Compressive strain
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Composite AnalysisUsing NASTRAN / PATRAN
• Ply‐13 (top) x‐direction strain fringe plot:
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2
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4Tensile strain
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Composite AnalysisUsing NASTRAN / PATRAN
• Printed Output File – Displacements:
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Composite AnalysisUsing NASTRAN / PATRAN
• Printed Output File – Element Forces (2D Shell):
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Composite AnalysisUsing NASTRAN / PATRAN
• Printed Output File – Reactions at Support:
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Composite AnalysisUsing NASTRAN / PATRAN
• Printed Output File – Ply Strains (2D Shell):
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Composite AnalysisUsing NASTRAN / PATRAN
• Printed Output File – Stresses (3D Solid):
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Composite AnalysisUsing NASTRAN / PATRAN
• Word of Caution ‐ Use of Offsets:
–Modeling with 2D shell elements–Meshing surface is the bottom surface– How do we model varying thicknesses?
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Composite AnalysisUsing NASTRAN / PATRAN
• Word of Caution ‐ Offsets:
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Composite AnalysisUsing NASTRAN / PATRAN
Thank You.
For questions, please contact me at:faeq_m_shaikh@hotmail.com
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