Diskussionsgruppe COMPOSITES

Composites Structures: Civil Airplanes Applications

Boeing 787 Airbus A350

In black the composite parts

Composites Structures: Automotive & Marine

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Composites Structures: Manufacturing & Civil

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MD NastranMD NastranMD NastranMD Nastran

MD Nastran

• Three major questions come up again and again

• What is it?– How does it differ from MSC.Nastran

• Backward Compatibility– Can I run my existing & legacy MSC.Nastran jobs?– Can I run my existing & legacy MSC.Nastran jobs?– Do I have to learn something new?

• What is the advantage?– What’s the payoff?

747-8 FEM

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MultiMulti--Discipline / MultiDiscipline / Multi--Scale Optimization (SOL400)Scale Optimization (SOL400)

MD Nastran Architecture

FE Optimization (SOL 200)

Structures /Mechanical

Thermal Dynamics/Aero, …

Adv NLAdv NL(Implicit,(Implicit,Explicit)Explicit)

MBSMBSServiceService

MSC/NASTRAN 1980 thru

19901990 thru

20002000 thru

20052005 thru

2009

Basic Basic NLNL

Nastran FootprintMore than Doubles

45 Years of Pedigree

2010+

Genoa integration NAI Sinda integration nCode integrationContact Algorithm

LS-Dyna

/Mechanical /Aero, …Explicit)Explicit) ServiceServiceNLNL

MD Framework (solver integration, 3MD Framework (solver integration, 3 rdrd party integration, scripting)party integration, scripting)

• The attractiveness of composites lies in their mechanical properties; such as weight, strength, stiffness, corrosion resistance, fatigue life. That is why the analysis of composite structures is imperative for the industries. The main advantage of composites is their flexibility in design. Mechanical properties of the laminate can be altered simply by changing the stacking sequence, fibre lay-up and thickness of each ply which leads to

Introduction to Composites: Technologies

sequence, fibre lay-up and thickness of each ply which leads to optimization in a design process.

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Classical Lamination Theory

Ed Dickerson

• Laminate effective material properties are tailored to meet performance requirements through the use of lamination theory integrated in the MSC.Software products.

• Used to accurately predict laminate properties. These analysis methods

θ= 0º, t=0.0125

θ= 45º, t=0.01

θ= 90º, t=0.01

θ= -45º, t=0.01

θ=0º, t=0.01

θ= -45º, t=0.0125

θ= 90º, t=0.0125

θ= 45º, t=0.0125

Classical Lamination Theory (CLT)

properties. These analysis methods address:

• Stress-strain relationship for membrane and bending response

• Thermal and moisture effects

• Inelastic behavior

• Strength and failure

• Interlaminar stresses

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• First-Ply Failure (FPF)– Linear analysis based on failure theory– Compute failure index or strength ratio

for the ply material– Optimization of ply angle/thickness

First-Ply-Failure Analysis

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Critical Margin of Safety

Access to MD Nastran Advanced Composite Solution

Extensive MD content now

• Progressive Failure Analysis• Adv. Progressive Failure Analysis • Fracture Mechanics and Delamination:

VCCT (Virtual Crack Closure Tecnique)• Delamination: Cohesive Zone Modeling• Delamination: Breaking glued contact• Delamination: Breaking glued contact• 3D Composites• Composites Beam

Progressive Failure Analysis

Ed Dickerson

Progressive Failure Analysis

• The progressive failure analysis is a method developed for predicting the nonlinear response and failure of laminated composite structures from initial loading to final failure.

• Failure is indicated by the failure criteria used.

• When failure occurs, the FEM element stiffness is degraded.

• The material will not heal; the damaged elements keep the degraded properties after unloading.

Progressive Failure Analysis

properties after unloading.

• Investigations of effect of overloads on composite structures• Available for existing criteria: Maximum Strain/Stress, Hill, Tsai-Wu • Available for NEW criteria: Puck, Hashin, Hashin-Tape, Hashin-Fabric

These failure theory are able to predict the failure load and also the mode of failure such as fiber failure and/or matrix failure.

Progressive failure

• How does failure affect the different material moduli ?

• Assume – 1-direction is fiber direction– 2-direction is matrix direction in the plane of the ply– 3-direction is through the ply thickness

• Fiber failure– Reduce E1 and E3

• Matrix failure– Reduce E2, G12, G23 and G31

Progressive Failure Analysis

Adv. Progressive Failure Analysis

Ed Dickerson

Adv. Progressive Failure Analysis

• GENOA is an integrated structural analysis software suite to predict strength, reliability and durability of structural composite components

• The use of material library from Genoa is available in MD Nastran.

Micromechanical Composite Material Definition

Nastran.• Based on constituent properties,

Fiber and Matrix, evaluates the structural and material response including degradation of material properties due to initiation and growth of damage.

• Over 20 Micro Mechanical Failure Criteria Failure Criteria available with MD Nastran Adv. PFA analysis

• It is a fully integrated solution, Genoa material stiffness evaluation is in the increment loop, MD Nastran calls Genoa for each element, damage reflected as modified stiffness.

2D Woven

LaminateComponent

FEMVehicle

Traditional FEM stops here Lamina

3D Fiber

Adv. Progressive Failure Analysis

• At each individual load step, the stresses and strains, obtained through the composite micro-stress analysis, are checked according to distinct failure criteria.

Unit cell at node

Sliced unit cell

Micro-Scale

Traditional FEM stops hereGENOA goes down to micro-scale

Lamina

FEM results carried down to micro scale Reduced properties propagated up to vehicle scale

Takes full advantage of MD Nastran capabilities and Genoa material library

Failure theories for Adv. Progressive Failure Analysis

• Longitudinal tension

• Longitudinal compression

• Transverse tension

• Transverse compression

• Normal tension

• Normal compression

• In-plane shear

• Transverse normal shear

• Fiber micro-buckling

• Tsai-Wu theory

• Hill theory

• Hoffman theory

• Maximum stresses theory

• Maximum strain theory

• First strain invariant failure

theory

• Longitudinal normal shear

• Modified distortion energy

• Inter-ply relative rotation

Honeycomb failure modes recognized

• Inter-ply relative rotation

• Fiber crashing

Wrinkling Crimping Dimpling

Genoa Integration: Modeling composite

materials at constituent LevelFusolage Stiffened Panel Adv. Progressive Failure A nalysis with Micromecanical material definition (Fi ber / Matrix)

Glued Contact between frames and panel

Micromechanical Damage IndexStress Strain

Fracture Mechanics and Delamination

Ed Dickerson

• Delamination is one of the main failure mechanisms in laminated composites• Possible reasons for delamination are:• Manufacturing defects and stress• Gradients near geometric discontinuities (like stiffener terminations and

bolted joints)• Delamination may result in local failure or even a significant loss of the

Delamination Introduction

• Delamination may result in local failure or even a significant loss of the structural integrity

• Three different approach available:

– VCCT– CZM– Breaking glued contact

(Virtual Crack Closure Tecnique)

• The VCCT is the fracture mechanics approach for studying delamination and crack initiation and growth.

• It is used for calculating the energy release rate of single or multiple cracks.

Fracture Mechanics with VCCT

• In linear fracture mechanics, a crack starts to grow when– Total G > Gc

– G is the energy release rate– Gc is the fracture toughness

(Virtual Crack Closure Tecnique)Fracture Mechanics with VCCT

– Gc is the fracture toughness

• VCCT is a methods used to compute the energy release rate.• Energy release rate:

G = Fu/2a

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(Virtual Crack Closure Tecnique)Fracture Mechanics with VCCT

Mode I: Opening

Mode II: Sliding

Mode III: Tearing

VCCT Example:

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• The so-called interface elements can be used to simulate the onset and progress of delamination. The constitutive behavior of these elements is expressed in terms of tractions versus relative displacements between the top and bottom edge/surface of the elements.

• Considering a 3-D interface element, the relative displacement components with respect to the local element system:

Cohesive Zone Modeling (CZM)Delamination:

components with respect to the local element system:

• The interface elements can be modeled between 2D and 3D structural finite elements:

• The effective traction is introduced as a function of the effective opening displacement, and is characterized by an initial reversible response followed by an irreversible response as soon as a critical vc effective opening displacement has been reached. Three standard functions are

Cohesive Zone Modeling (CZM)Delamination:

opening displacement has been reached. Three standard functions are currently available

Cohesive Zone Modeling: examples

DCB

Test Specimen

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Delamination of NASA Test

Specimen

Test Specimen

• Release glued contact when stress criteria is satisfied:

Breaking glued contactDelamination:

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• Use contact normal and tangential stress

• After break, do regular contact with friction and separation

Breaking glued contact: examples

Stringer termination analysis

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Shear Stiffened Panel Analysis

Continuum Elements are required for Composites Modelling:

• When detailed out-of plane stress recovery are needed

• When transverse shear effect are predominant

3D composites

• When accurate interlaminate stresses such near localized region of complex loading or geometry

• When better contact condition are needed

Detailed out-of plane stress recovery3D composites: Examples

Three Point Bending Test

Free-Edge Delamination

Composites Beam

Ed Dickerson

Composites Beam

Composite Beam Using the Variational AsymptoticMethod (VAM)

• Arbitrary beam cross section (ABCS) capability available in MD Nastran, and composite support for an arbitrary beam cross section has been implemented. The variational asymptotic method (VAM) is used to compute the beam properties of an arbitrary cross section.

• The composite beam using VAM provides an alternative to conventional 3-D/2D modeling technique, and permits the use of beam element to model composite beams. The layup of composite beam plies is described model composite beams. The layup of composite beam plies is described on the PCOMP/PCOMPG Bulk Data entries. In addition, the cross section of the composite beam can be expressed conveniently with the CP/OP options of the PBMSECT Bulk Data entry

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• Examples of Composites Beam Bulk Data Entry:

Composite Beam Using the Variational AsymptoticMethod (VAM)

• PBMSECT,32 is a box beam made of composite material. All segments have a common CORE=204 with four plies. Segments from POINTs 2 through 5 have one ply on top, layer=(210,101), and one ply at the bottom, L(2)=(210,103).

• Limitations

• Beam must be straight when used as a composite beam (not curved).

• SOL 200 does not yet support the composite beam.

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• MSC.Software expertise is proven by the collaboration with all main global players in the Composites Material market

• MSC.Software solutions are already succefully applied in any stage of composites products development

• MSC.Software local team is highly experienced in delivering and implementing our solutions to customers

Conclusions:

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implementing our solutions to customers

Largest Autoclave in the World Statistics:Inside working diameter: 30ft. (9.26M)Ouside diameter: 32ft. (9.88M)Inside working length: 76 ft. (23.5M)Overall length: 112 ft. (34.5M)Vessel volume: 82,000 cu.ft.Max temperature: 450FMax pressure: 150 psigVought Aircraft in Charleston, SC

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Ing. Armando MetePreSales EMEAEuropean Composite Material Technical Expertarmando.mete@mscsoftware.com

http://www.mscsoftware.com/