A multiscale strategy for the simulation of braided composites with ENVYO

Abstract

Manufacturing processes and parameters have played a crucial role in the design and analysis of composite structures. To exploit potential advantages of composite materials, it is necessary to predict and optimize the manufacturing steps in respect to the optimization of the structure itself. During the past years, the project DigitPro (Digital Prototype) has been developed within the research campus ARENA2036. A multiscale simulation strategy is investigated to cover a full product generation cycle of textile composite components from structure pre-design up to part manufacturing. Start parameters are firstly identified for each step of the cycle. Subsequently, appropriate materials, geometries and manufacturing parameters are found during optimization loops. Finally, the result is sent into real manufacturing process. The mapping tool ENVYO stands as a connector between the various simulations and simulation softwares. Hence, ENVYO allows the transmission of information from one simulation to another. The presentation will focus on two key aspects of the simulation of textile composites. On the mesoscopic scale, detailed finite-element models of the textile laminate are generated, representing closely the complex yarn architecture. The mechanical properties of the laminate are numerically identified by simulating the models under tension, compression and shear loading. The transition to the structure simulation on macroscopic scale is performed via the tool ENVYO following two approaches. The first approach directly uses the material properties generated on the mesoscale for the structure simulation. In the second approach, information from the process simulation is mapped on the structure mesh to take into account the influence of local yarn architecture on the structural behaviour. Both methods will be compared to standard structure simulation and to experimental results. The developed methodology will be illustrated with the example of braided composites and the potential of the process chain will be discussed.

Full text

ARENA2036 DigitPro: Digital Prototype
A Multiscale Strategy for the Simulation of Braided Composites with ENVYO
17. Oktober 2018
LS-DYNA Forum 2018, Bamberg
Mathieu Vinot, Martin Holzapfel, Christian Liebold

DigitPro – Digital Prototype
braided structures
Open-Reed-Weaving parts
-50% development time
min. -10% weight
closed, numerical process chain
from the presizing to the final product
simulation on the meso and macroscale
various simulation tools
HDF5 format
Draping simulation
DIGITALER
PROTOTYP
Structure analysis
Structure optimisation
Braiding robot
Braiding simulation
Virtual braid
mapping tool
ENVYO

Experimental investigation
stepwise failure
 different yarn
strengths (material
variability)
linear behavior
 tension and
compression loading
of axial yarns
structural integrity
 loading of
braiding yarns
high reproduceability of braiding process
transfer of test condition in the simulation (impactor and support displacement, testing speed etc.)
Investigation of a braided reinforcement structure under quasistatic 3-point bending
complex structure geometry  potential deffects due to manufacturing conditions
use as reference for the investigation of different modelling approaches
Displacement
Force

4
1 – Standard approach

3. Structure simulation without tuning
Overprediction of structural strength
4. Changes of material parameters  try-and-error
 no predictive simulation, only a post-test simulation
5
Reference approach
1. Modelling with UD-plies
2. Calculation of yarns stiffness and strength
Use of material properties from datasheets
30°
-30°
0°
-30°
30°
Principle of the approach
Analytical calculation according to Chamis „Mechanics of composite
materials: past, present, and future, NASA TM-100793, 1984”
Matrix
Fibre
FVC
Yarn

3. Structure simulation
6
Reference approach
1. Modelling with UD-plies
2. Calculation of yarns stiffness and strength
Use of material properties from datasheets
Principle of the approach
Advantages
„universal“ approach (weave / UD...)
fast model generation
low computing time
Drawbacks
local effects are not considerated
fibre architecture is not reproduced
adjustment cycles necessary
overpredictive if not tuned
Analytical calculation according to Chamis „Mechanics of composite
materials: past, present, and future, NASA TM-100793, 1984”
30°
-30°
0°
-30°
30°

7
2 – Multiscale approach

8
Example of a 30°-triaxially braided laminate – compaction simulation
Simulation on the mesoscale
Breite = 𝑓
1𝜃, 𝑑, 𝑘, η
Länge = 𝑓
2𝜃, 𝑑, 𝑘, η
Lücke = 𝑓
3𝜃, 𝑑, 𝑘, η
Braiding angle
Braiding core diameter
Size of yarn
FVC
CT-Scan
Parametric model of the dry textile

9
Simulation on the mesoscale
Example of a 30°-triaxially braided laminate – tension simulation
Data for generation of a material card (E11, E22, S11, S22...)
Transverse failure [-] Unit cell number 2

10
Structure simulation of the reinforcement structure
automatic postprocessing of unit cell results with ENVYO
generation of material cards for the different textile types
Simulation on the mesoscale
Virtual material data
MAT_262_LAMINATED_FRACTURE_DAIMLER_CAMANHO
CONTACT_SURFACE_TO_SURFACE_TIEBREAK
MAT_187_SAMP-1

11
Predictive structure simulation of the reinforcement structure
Simulation on the mesoscale
Stiffness prediction
Strength prediction
Prediction of residual strength
delayed failure of axial yarns
Force
Displacement
Multiscale approach

12
Structure simulation of the reinforcement structure
Simulation on the mesoscale
Multiscale approach
Force
Displacement
Advantages
consideration of textile architecture
realistic textile behaviour in simulation
automatisation possible
predictive simulation, no tuning
Drawbacks
increased computing times
more complex model generation

13
3 – Process chain approach

14
Braiding simulation
Process chain approach
Machine parameters
Number of bobbins
Fibre typ
Yarn pretension
Braiding Speed
Robot path
Simulation model
Manufacturing effects
Orientation
Ondulation
Dry spots
Gaps to core
Opt. machine parameters
Gaps in the braided textilte
Gap between yarn and
braiding core  matrix-
rich zones
Digital Twin
Original textile architecture after braiding simulation

15
Braiding simulation
Process chain approach
Machine parameters
Number of bobbins
Fibre typ
Yarn pretension
Braiding Speed
Robot path
Simulation model
Manufacturing effects
Orientation
Ondulation
Dry spots
Gaps to core
Opt. machine parameters
Digital Twin
Upper movable mould
Lower fixed mould Braided textile with closed gaps
Closing of the gaps

Simulation
16
Information mapping to structure mesh
Process chain approach
Model from the braiding simulation
Mapping of:
Yarn orientations
Ondulation
Dry spots
Yarn geometry (width/thickness)
Resin
PID 1001
PID 1002
PID 1002
MID 1002
MID 1001
MID 24
MID 1002
MID 1001
MID 1002
MID 1002
neighbour element
t1
t1 < t2

17
Process chain approach
Structure simulation with mapped information
Stiffness prediction
Strength prediction
Prediction of residual strength
Prediction of yarn influence on local strain field
Tension-loaded axial yarns
(compression-loaded on the lower side)
Shear-loaded braiding yarns
Plastic deformation of the structural foam
Force
Displacement

18
Process chain approach
Structure simulation with mapped information
Stiffness prediction
Strength prediction
Prediction of residual strength
Prediction of yarn influence on local strain field
Force
Displacement
Advantages
consideration of textile architecture
realistic textile behaviour in simulation
automatisation possible
local strain field can be predicted
Drawbacks
increased computing times
more complex model generation
investigation of information mapping
with ENVYO is necessary

19
Conclusion
mapping tool as link between process simulations and structure simulations
transfer and simplification of information from the mesoscale to the macroscale
a sensitivity analysis have to be performed before starting the structure simulation
increase of prediction capabilities of structure simulation
Mesoscale
process simulation
reduction of experimental effort
increased structure quality
through optimisation loops
Macroscale
structure simulation
consideration of manufacturing
effects
relative low CPU time
Envyo
HDF5 format Displacement
Force
Mapping
Unit cell
Reference

20
Mathieu Vinot
mathieu.vinot@dlr.de
Questions & Discussion
Thank you very much for your attention