Diskussionsgruppe COMPOSITES

Transcription

1 Diskussionsgruppe COMPOSITES

2 Composites Structures: Civil Airplanes Applications Boeing 787 Airbus A350 In black the composite parts

3 Composites Structures: Automotive & Marine 5/19/2011 3

4 Composites Structures: Manufacturing & Civil 5/19/2011 4

5 MD Nastran

6 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? Do I have to learn something new? What is the advantage? What s the payoff?

7 747-8 FEM 7

8 MD Nastran Architecture Nastran Footprint More than Doubles MSC/NASTRAN 1980 thru thru thru thru Years of Pedigree Multi-Discipline / Multi-Scale Optimization (SOL400) FE Optimization (SOL 200) Structures /Mechanical Thermal Dynamics /Aero, Basic NL Adv NL (Implicit, Explicit) MBS Service MD Framework (solver integration, 3 rd party integration, scripting) Genoa integration Contact Algorithm NAI Sinda integration ncode integration LS-Dyna

9 Introduction to Composites: Technologies 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 optimization in a design process. 5/19/2011 9

10 Classical Lamination Theory Ed Dickerson

11 Classical Lamination Theory (CLT) 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 address: Stress-strain relationship for membrane and bending response Thermal and moisture effects Inelastic behavior Strength and failure Interlaminar stresses θ=0º, t=0.01 θ= 45º, t= θ= -45º, t=0.01 θ= 90º, t= θ= 90º, t=0.01 θ= -45º, t= θ= 45º, t=0.01 θ= 0º, t= /19/

12 First-Ply-Failure Analysis 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 Critical Margin of Safety 12

13 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 3D Composites Composites Beam

14 Progressive Failure Analysis Ed Dickerson

15 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. 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.

16 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 E 1 and E 3 Matrix failure Reduce E 2, G 12, G 23 and G 31 Progressive Failure Analysis

17 Adv. Progressive Failure Analysis Ed Dickerson

18 Micromechanical Composite Material Definition 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. 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

19 Adv. Progressive Failure 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. At each individual load step, the stresses and strains, obtained through the composite micro-stress analysis, are checked according to distinct failure criteria. Vehicle Component FEM 3D Fiber Laminate Traditional FEM stops here GENOA goes down to micro-scale Micro-Scale FEM results carried down to micro scale Sliced unit cell Reduced properties propagated up to vehicle scale Lamina 2D Woven Unit cell at node Takes full advantage of MD Nastran capabilities and Genoa material library

20 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 Longitudinal normal shear Modified distortion energy Inter-ply relative rotation Fiber micro-buckling Tsai-Wu theory Hill theory Hoffman theory Maximum stresses theory Maximum strain theory First strain invariant failure theory Inter-ply relative rotation Fiber crashing Wrinkling Crimping Dimpling Honeycomb failure modes recognized

21 Genoa Integration: Modeling composite materials at constituent Level Fusolage Stiffened Panel Adv. Progressive Failure Analysis with Micromecanical material definition (Fiber / Matrix) Stress Strain Micromechanical Damage Index Glued Contact between frames and panel

22 Fracture Mechanics and Delamination Ed Dickerson

23 Delamination Introduction 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 structural integrity Three different approach available: VCCT CZM Breaking glued contact

24 Fracture Mechanics with VCCT (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.

25 Fracture Mechanics with VCCT (Virtual Crack Closure Tecnique) In linear fracture mechanics, a crack starts to grow when Total G > G c G is the energy release rate G c is the fracture toughness VCCT is a methods used to compute the energy release rate. Energy release rate: G = Fu/2a 25

26 Fracture Mechanics with VCCT (Virtual Crack Closure Tecnique) Mode I: Opening Mode II: Sliding Mode III: Tearing

27 VCCT Example: 27

28 Delamination: Cohesive Zone Modeling (CZM) 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:

29 Delamination: Cohesive Zone Modeling (CZM) 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 currently available

30 Cohesive Zone Modeling: examples DCB Test Specimen Delamination of NASA Test Specimen 30

31 Delamination: Breaking glued contact Release glued contact when stress criteria is satisfied: Use contact normal and tangential stress After break, do regular contact with friction and separation 1/7/

32 Breaking glued contact: examples Stringer termination analysis Shear Stiffened Panel Analysis 32

33 3D composites Continuum Elements are required for Composites Modelling: When detailed out-of plane stress recovery are needed When transverse shear effect are predominant When accurate interlaminate stresses such near localized region of complex loading or geometry When better contact condition are needed

34 3D composites: Examples Detailed out-of plane stress recovery Three Point Bending Test Free-Edge Delamination

35 Composites Beam Ed Dickerson

36 Composite Beam Using the Variational Asymptotic Method (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 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 5/19/

37 Composite Beam Using the Variational Asymptotic Method (VAM) Examples of Composites Beam Bulk Data Entry: 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. 5/19/

38 Conclusions: 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 5/19/

39 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: 450F Max pressure: 150 psig Vought Aircraft in Charleston, SC Ing. Armando Mete PreSales EMEA European Composite Material Technical Expert 39