Bridging the Gap between Autodesk Moldflow and Nonlinear FEA of Reinforced Plastic Parts Dr. Roger A. Assaker CEO, e-Xstream engineering Chief Material Strategist, MSC Software

Class Objectives To learn about the latest developments in modeling nonlinear behavior of structures made of fiber reinforced plastics, including: Long Fibers & MuCell Materials Injection and Compression Molding Compression Fatigue and Creep Performance High Performance Computing

Class Structure Introduction & Motivation Compression Molding Long Fiber Reinforced Plastics MuCell Fatigue Creep Hybrid Solution Procedure

Introduction & Motivation

Composites in Automotive

Opportunities: Weight Reduction Average/Indicative Facts: 1995  2005: +17% of mass (1118 kg1310kg) +200 kg  +18% of Fuel consumption (4.8 l/100km  5.7 l/100km)  Objective : -200 kg or -15 to 20 g CO2/km by 2020 Plastic parts: interior, under the hood, … Optimize using advanced CAE/Material Modeling Optimize design: e.g. engine mount: -40% weight & -15% in cost Reduce thickness Part consolidation Metallic parts: Platform, Cabin Frame, Skin,… Optimal mix of materials : Plastics, Composites, …

Mutli (Composite) Materials

Chopped Fibers/Injection Molding Fully aligned flow Flow lines Weld lines

Challenges of Reinforced Plastics Process-dependent (Local) Moldflow (Fiber orientation) Nonlinear Stain-rate dependent Anisotropic

Process  Material  Structure Material Processing Injection molding Compression modling D-LFT Material Microsturcure Chopped fibers Nano, ... Material Chracteristics Mechanical Thermal Electric, ... Structural Performance Stiffness Strength Fatigue, … …

Material Behavior: Measured Source: LKT, Prof. Drummer Friedrich-Alexander-Universität Erlangen-Nürnberg Skin-core effect Source: DatapointLabs e-Xstream Users‘ Meeting 2011

Measured Properties  FEA ? Material properties from ISO 527 specimen Average orientation OT{Trace} = [ 0.80 | 0.15 | 0.05 ] Scaling (factor = 0.6 – 0.8) Material properties from injection molded plate 0° properties Scaling (factor = ???) 0° / 30° / 45° / 60° / 90° properties Reverse engineering Skin-Core effect OT = [ multi-layer RVE ] Global isotropic Local anisotropic

Local, Nonlinear, Anisotropic Material Loading ISO 527 100% 2D 36% IM 22%

Local Results: Plastic Strain equivalent scaling isotropic anisotropic With Moldflow & Digimat) Without Moldflow & Digimat)

Local Results: Weldline Fiber orientations Accumulated plastic strain in material matrix

Materials: Long Fiber Thermoplastics (LFT)

LFT – Effect of Fiber Waviness Tortuose Straight

LFT – Effect of Fiber Bundling s11 [MPa] e11 Without bundling With bundling ~ 2300 MPa ~ 2800 MPa + ~ 500 MPa

LFT - Effect of Bundling in Digimat-MF ar = 50 ar = 5 + 5% fibers 5% bundling s11 [MPa] e11

Materials: MuCell

MuCell RVE Generation 15 % fibers 20 % voids Source: http://www.genesisllc.com/gpe/images/mucell_glass.gif 15 % fibers 20 % voids

Strain Distribution in the Microstructure Tensile Direction mean local Tensile Direction

MuCell: Effect of Void on the Material Stiffness aligned

MF vs FE modeling of MuCell 7.8% voids 15% voids

MuCell: Distribution of the VF of Air Inclusions

MuCell: 3-Point Bending Beam

MuCell: Armrest Vertical Load

MuCell: Horizontal Side Impact

MuCell: Horizontal Impact CAE Performance Curves

Performance: Fatigue

Chopped Fiber Reinforced Plastics: Fatigue Analysis Workflow DIGIMAT reinforces the fatigue life computation at two levels: Computation of the unit load case (Digimat-CAE/Structural) Computation of the fatigue life prediction (Digimat-CAE/Fatigue)

Fatigue: Chopped Fiber Reinforced Plastics

First Pseudo Grain Fatigue (FPGF) Model Ply composite Using fatigue failure criteria (i.e. Tsai-Hill) Pros : Different « strengths » per direction, multi-axial Cons : Purely meso/macro if not coupled with multi-scale methodology Tsai-Hill S: Fatigue strengths depending over N (nb cycles to failure) 1/L: Fiber direction 2/T: Transverse direction Users workflow Exp measurement: S-N curves measured for 0°, 45° 90° UD specimens Material modeling: Define the measured S-N curves and corresponding microstructure (0° vs 90°) Fatigue solution: Prediction of local S-N curves in each integration point (ply in each element) of the FE model, accounting for any Stress amplitude Mean stress Loading direction / Fiber alignment Damage accumulation:  Miner’s rule Tensile 0° Tensile 90°

Fatigue of Chopped Fiber Reinforced Plastics Unit Load: Stress S11 Fatigue life

Creep & Relaxation

Creep & Relaxation

Creep: Affine vs General vs Spectral vs FE

Thermo-ViscoElasticity

Thermo-ViscoElastic Relaxation

CPU Optimization: Digimat Hybrid

Hybrid Solution Procedure

Crush Simulation: Digimat-CAE/LS-Dyna

Digimat Nonlinear Micro Material Model Bumper Beam impact Material definition Digimat v4.3.1 Viso-plastic propety FPGF failure Tsai-Hill-2D strains Micro: strain base Hybrid: stress base Mircostructure Morphology Orientation Length: Short Fibers (AR=20) Weight Fraction of Fibers Isotropic Use MD property from Digimat-MF result Viso-plastic property Failure : end point of MF curve MD FPGF failure defined at this strain-rate TD

Optimal Domain Decomposition Optimization Decomposition Default decomposition 29 domains have no Digimat elements Digimat elements in 3 domains Improved decomposition Digimat elements in 22 domains 10 domains have no Digimat elements Optimized decomposition Almost same as improved but all domain has Digimat elements.

CPU Performance: Digimat vs Isotropic Hybrid Hybrid 16 cores 32 cores 64 cores Iso (improved) 17 h 59 m 9h 17m 10h 0m Hybrid (default) - 42h 31m 26 h 37 m 14h 16m 8 h 15 m (optimized) 12h 5m Micro 152 h 51 m (6.4 days)

Conclusions Reinforced Plastics is a light weight alternative to metals Advanced CAE, including nonlinear multi-scale material modeling , enables effective & efficient design of reinforced plastic parts by Taking advantage the process simulation done with Moldflow The latest developments in Multi-Scale Material & Structural Modeling support: Long Fiber and MuCell Fatigue and Creep Performance Hybrid Solution Procedure and HPC make Nonlinear Multi-Scale a efficient solution procedure for accurate part and system simultion

Autodesk, AutoCAD* [*if/when mentioned in the pertinent material, followed by an alphabetical list of all other trademarks mentioned in the material] are registered trademarks or trademarks of Autodesk, Inc., and/or its subsidiaries and/or affiliates in the USA and/or other countries. All other brand names, product names, or trademarks belong to their respective holders. Autodesk reserves the right to alter product and services offerings, and specifications and pricing at any time without notice, and is not responsible for typographical or graphical errors that may appear in this document. © 2012 Autodesk, Inc. All rights reserved.