Slide 1

Modeling of Fiber Reinforced Structures in HyperMesh

Dr.-Ing. U. Weerts, Dr.-Ing. R. Kickert

, Lilienthalplatz 5, 38126 Braunschweig, Germany

Fiber reinforced polymers are today increasingly used in all types of components. A time efficient simulation process with a tight quality assurance is needed, especially with large numbers of parameters being involved for describing material and failure characteristics. A modular concept for the design of fiber reinforced structures is presented. As most of the “state of the art” ply failure criteria are not supported by commercial finite element programs, pre- and post-processing tools must be modified in a easy to use way by user-programmable features.

Libraries of material data including all essential strength properties and ply specific data are combined in a spreadsheet program to laminate properties. These are transferred to HyperMesh via the HMASCII interface using collectors including material data and ply specific data by card images. With the provided geometry the structured meshing capabilities of HyperMesh are used, to build up the finite element model. The analysis and post-processing is done with the commercial FE-program ANSYS. The necessary ply failure criteria considering static and fatigue behavior are implemented by user-programmable features, to support an efficient in time reporting.

Slide 2

Company Review

Blade root – hub connection (REpower)

Train nose section (Voith)Motorsailplane eta η

Circular antenna (DLR)

Inhouse-code development

Slide 3

Introduction

• FE-Modeling of FRP-structures is time-consuming caused by numerous parameters– material and strength properties (fiber failure,

intralaminar failure) for all used fabrics– many regions with different laminat lay-up

– material, orientation and thickness of each layer• Most “state of the art” failure criteria are not supported by

commercial FE-programs• Many not supported layer- or ply-based results-

representations in commercial FE-programs

Slide 4

Static Failure Criteria for FRP• Fiber- and intralaminar-

failure– UD-plies: Puck(1),

Hoffman, Tsai-Wu, ...– Biaxial Fabrics:

a) Devide into two UD-plies using Puck, ...

b) fabric-failure-criteria,intralaminar shear load is separated

• Core-failure: criteria based on transverse shear loads• Interlaminar failure: fracture mechanical criteria

UD-failure criteria(Puck)

Slide 5

Fatigue Failure Criteria for FRP• Fiber-, intralaminar- and core-failure:

– principal of the critical section plane(non-proportional loading)

– Calculation of range-mean-loading by the utilization degrees of the used failure criteria

– damage accumulation with Wöhler-rule and mean-stress-effect (e.g. Goodman-relationship(2))

• Interlaminar-failure:– the crack plane is the interface plane– energy based crack-propagation-analysis (e.g. Paris-

law)

intralaminar section plane

Slide 6

Modular Design Concept

Material-library

Ply-data

Region-Collectors

Data of fabrics

Laminat lay-up

Preprocessing

Solver

Postprocessing

Geometry, Loads, BC

Failure criteria of FRP

Spreadsheet

Slide 7

Material Properties and Ply-data• Spreadsheet based library of elasticity- and strength-

properties for static and fatigue-loads

• Properties depend nonlinear on the fiber-volume-fraction

Material properties

Nr. Description θθθθF ρρρρ L E1 E2 νννν12 G12 αααα1 αααα2 R1(+) R1

(−) R2(+)

/( ) /(kg/m³) /(GPa) /(GPa) /( ) /(GPa) /(10-6) /(10-6) /(MPa) /(MPa) /(MPa)

1 2AX090-Fabrics-E-Glas 0.45 1780 20.000 20.000 0.100 3.000 4.000 4.000 280.00 280.00 280.002 Foam-C70.55 --- 60 0.045 0.045 0.250 0.018 80.000 80.000 1.30 1.30 1.3034

Ply-data

Nr. Description Mat.-Nr. qF tL/( ) /(g/m²) /(mm)

1 2AX090-Fabrics CS-ITG 92110 1 163 0.142 2AX090-Fabrics CS-ITG 92125 1 280 0.243 Foam-C70.55 2 --- 1.0045

• Ply-data with material-reference and fiber-grammage

Slide 8

Laminat Lay-up• The laminat lay-up is combined in Region-Collectors

• Each Region-Collector is assigned to an element-type• Each layer is defined by the quantity of the plies, the sort-

number and their orientationsPly-data Elementtype

Nr. Description qF tL Nr. K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 K11/(g/m²) /(mm)

1 2AX090-Fabrics CS-ITG 92110 163 0.14 1 16 0 02 2AX090-Fabrics CS-ITG 92125 280 0.24 2 16 0 13 Foam-C70.55 --- 1.00 3 16 0 2

Laminate lay-up

LayernumberBOTTOM

Nr. Region Collector nL tL ITYPE LSYM ADMS L1 L2 L3 L4 L5 L6/( ) /(mm) /( ) /( ) /(kg/m²) Qty Ply Ori Qty Ply Ori Qty Ply Ori Qty Ply Ori Qty Ply Ori Qty Ply Ori

/( ) /( ) /(°) /( ) /( ) /(°) /( ) /( ) /(°) /( ) /( ) /(°) /( ) /( ) /(°) /( ) /( ) /(°)2 2 2 1 1 1 2 2 2 1 1 1 2 2 2 0 0 0

1 Example Region 1 5 3.77 3 1 1 0 1 2 45 3 3 0 1 2 45 1 1 02 Example Region 2 5 3.28 3 1 1 0 3 3 0 1 1 034

SHELL91SHELL91SHELL91

Name Remark

Nodes at middle surfaceNodes at bottom surfaceNodes at top surface

ANSYS HMASCII

Slide 9

HyperMesh-Interface(3)

• The collected spreadsheet-data are transferred via a HmAscii-File

• Material data including strength properties are assigned to Material-Collectors

• The laminat lay-up is saved in Property-Collectors

• Component-Collectors are defined with property- and element-type-reference

• The element-type definitions are saved in Sensor-Collectors

HYPERMESH Input Deck Generated by leichtwerk : 2.0Generated using leichtwerk-HmAscii Template Version : 2.0*filetype(ASCII)*version(8.0)

BEGIN DATA

BEGIN MATERIALS*material(1,"2AX090-Fabrics-E-Glas",7)*attributesforentity(MATERIALS,1,67)*attributeint(1,500,0,0,8)...

END MATERIALS

BEGIN PROPERTIES*property(1,"Example Region 1",0,7)*attributesforentity(PROPERTIES,1,10)*attributeint(0,3032,0,0,8)...

END PROPERTIES

BEGIN COMPONENTS*component(1,"Example Region 1",1,5)*attributesforentity(COMPS,1,3)*attributeint(0,3080,0,0,8)...

END COMPONENTS

BEGIN SENSORS*sensor(1,"SHELL91_MID")*attributesforentity(SENSORS,1,14)*attributeint(0,1202,0,0,8)*attributeint(91,141,0,0,8)...

END SENSORS

END DATA

Slide 10

Preprocessing (HyperMesh)

FE-Model of a train nose section (Voith)

• Geometry is imported by IGES-interface

• Geometry is organized by the predefined region-collectors

• FRP-parts are meshed with second-order-elements

• The structured meshing capabilities of HyperMeshare used

• Bondings are realized with second-order-solids

Slide 11

Solver and UPF• The analyses are performed

with ANSYS

• Therefore, the HyperMeshADPL-Interface is used

• Aerodynamic surface loads are applied via an external Nastran BDF-interface

• The layer based static-and fatigue-failure-criteria are included by User-Programmable-Features (UPF)

Pressure distribution of a train nose section (Voith)

Slide 12

• following items are currently supported for static analysis:

– Intralaminar-failure-index– Intralaminar-failure-mode– Intralaminar-failure-angle

– Fiber-failure-index– Layer stresses and

strains

– Layer orientations– Core-failure-index– Core shear stresses

Postprocessing

Fiber-Failure-Index

Intralaminar-Failure-ModeIntralaminar-Failure-Index

Slide 13

• following items are currently supported for fatigue-analysis:

– Intralaminar-failure-index– Fiber-failure-index– Core-failure-index

• damage accumulation can be performed for– Range-mean-matrices with

serial consideration of multiple unit-loadcases

– Load-time-series with superposition of unit-loadcases(principle of the critical section plane)

PostprocessingRange-mean-matrix of a

blade root section

Slide 14

Summary• modular design to combine the potentials of the programs

– Spreadsheet based material libraries

– Spreadsheet based laminat-modeler

– Preprocessing with HyperMesh

– Solver ANSYS

– Postprocessing with customized ANSYS

• currently analyses of static- and fatigue-behavior of UD-plies, several fabrics and cores are supported

Material-library

Ply-data

Region-Collectors

Data of fabrics

Laminat lay-up

Preprocessing

Solver

Postprocessing

Geometry, Loads, BC

Failure criteria of FRP

Spreadsheet

Slide 15

Further Activities and Outlook

• Implementation of failure analysis of metals (FKM-guidlines(4))

• Solver independent failure analysis, therefore implementation of failure criteria and layer based output in HyperView

• Extension of the HyperMeshADPL-Interface by customized Bonding-Interface-Elements(5)

(J-Integral, Crack-Propagation)

Crack-propagation-analysis of a bonded repair

▬ B-Basis ▬ Regression

Slide 16

References

(1) A. Puck, Festigkeitsanalyse von Faser-Matrix-Laminaten, München, 1996(2) Germanischer Lloyd, Richtlinie für die Zertifizierung von

Windenergieanlagen, Hamburg, 2003.

(3) HyperMesh User’s Manual, Version 8.0(4) Forschungskuratorium Maschinenbau, Rechnerischer Festigkeitsnachweis

für Maschinenbauteile, Frankfurt a.M., 2003

(5) Ulf Weerts, Bruchmeschabische Charakterisierung von Klebungen, Ph.D. thesis, Institut für Flugzeugbau und Leichtbau, TU-Braunschweig, Braunschweig, 2004