1. WP3. Optimization using computer methods properties of new materials and structural elements made of them
Brief description of the WP3
Jānis Šliseris
Senior Researcher, Dr.Sc.Ing.

2. Outline Involved partners Main tasks Description of task 1

3. Involved partners
RTU- Riga Technical University- Jānis Šliseris - Supervisor
UPT- Polytechnic University of Timişoara- Dan-Andrei ŞERBAN
UNMdP- University of Mar del Plata - Exequiel Santos Rodríguez

4. Main tasks
Task1. Analysis and optimization of material to be maximally effective for mechanical loading
Task2. Estimation of environment and temperature impact on the material

5. Task1. Analysis and optimization-Simulation work-flow
Sub-task 1. Micro scale simulations of representative volume elements (RVE)
Sub-task 2. Macro-scale simulation of beam with matrix (fly-ashes) and short fibers from waste
Sub-task 3. Macro-scale simulation of beam with matrix (fly-ashes) and short fibers from waste, and possible combination with traditional steel (or other material, e.g. basalt) bar reinforcement.
Sub-task 4. Optimization of fiber content, matrix parameters, reinforcement bar configuration
For validation purposes, the Mori-Tanaka analytical approach can be used

6. Task1. Analysis and optimization
Sub-task 1. Micro scale simulations of representative volume elements (RVE)
Conceptual description:
Research and development of an algorithm for generation RVE’s geometry, including matrix, random fibers, random inclusions etc. Finite element discretization or voxel based discretization
Research on existing models or implementation of appropriate material constitutive model using UMAT (user defined material subroutine usually in FORTRAN or c++ language) subroutine for matrix and fibers separately
Use/development of an effective scale transition algorithm (typically used FE2 approach, but recommended to use a database approach
Necessary INPUT data:
Stress-strain curves (experimentally obtained or from literature) for matrix (fly-ashes) in static and cyclic compression (and tension if possible) load
Stress-strain curves for fibers in static tension load. Crack patterns. If possible, cohesive properties of aggregates are important.
Average fiber orientation characteristics (may be estimated indirectly by compression tests in 3 different directions or directly by CT (computer tomography)-scan-?)
Histograms for fiber length and diameter statistical distributions. Granulometry!!!

7. Task1. Analysis and optimization
Sub-task 1. Micro scale simulations of representative volume elements (RVE)
OUTPUT data:
Virtual model on microscale
Material stiffness matrix (tensor) depending on strain state
In database method there will be a database with material stiffness characteristics (Young modulus, Shear modulus, Poisson’s ratio), strength characteristics (failure stress in tension and compression), depending on the strain state.
Figures from: Janis Sliseris, Libo Yan, Bohumil Kasal, Numerical modelling of flax short fibre reinforced and flax fibre fabric reinforced polymer composites, Composites Part B: Engineering, Volume 89, 15 March 2016, Pages

8. Task1. Analysis and optimization
Sub-task 2. Macro-scale simulation of beam with matrix (fly-ashes) and short fibers from waste
Conceptual description:
Development of finite element model for beam 3-point bending test using solid finite elements (or lattice based model)
Constitutive model that is based on the previously computed database with materials characteristics (Young’s modulus etc.)
Validation of numerical model
Generation of a non-linear beam finite element model for modeling of realistic concrete building frame using validation data.
Necessary INPUT data:
Material stress-strain curves in compression and tension. Fiber pull-out test for estimation of bridging forces.
3-point bending test results of the beam(s) with chosen matrix and fibers
OUTPUT data:
Structural behavior (macroscopic stiffness, load-displacement curve, joint stiffness) of beam and/or frame structures using proposed materials

9. Task1. Analysis and optimization
Sub-task 3. Macro-scale simulation of beam with matrix (fly-ashes) and short fibers from waste, and possible combination with traditional steel (or other material, e.g. basalt) bar reinforcement.
Conceptual description:
Development of finite element model for beam 3-point bending test using solid finite elements (or lattice-based model) for fiber-concrete and link type finite elements for reinforcing bars.
Constitutive model that is based on the previously computed database with materials characteristics (Young’s modulus etc.)
Validation of numerical model
Generation of a non-linear beam finite element model for modeling of realistic concrete building frame using validation data.
Necessary INPUT data:
Material stress-strain curves in compression and tension
Reinforcement bar tension test stress-strain curves
3-point bending test results of the beam(s) with chosen matrix and fibers
Cohesive properties between reinforcement bar and concrete. Fiber pull-out test in different angles!!!
OUTPUT data:
Structural behavior (macroscopic stiffness, load-displacement curve, joint stiffness) of beam and/or frame structures using proposed materials

10. Task1. Analysis and optimization
Sub-task 4. Optimization of fiber content, matrix parameters, reinforcement bar configuration
Conceptual description:
Development a link between structural analysis software (e.g. Abaqus, ANSYS or Code_Aster) and optimization software (e.g. MATLAB and Artifical Neural Network)
Objective functions: maximal specific strength or stiffness
Variable parameters: granulometric characteristics, amount of fibers, fiber orientation (if possible), type of fibers (possible combination of different fibers, including tradition fibers), length of fibers, matrix properties, such as, type of fly-ashes
Necessary INPUT data:
Recommendations of the most important parameters of material structure that can be varied in manufacturing process
Technological restrictions of material manufacturing. This include description of intervals in which practically the variable parameters can be changed.
OUTPUT data:
Estimation of optimal material internal structure
Suggestions for further development directions

11. Task2. Estimation of environment and temperature impact on the material
Sub-task 1. Numerical estimation of low (around -20 degrees- winter climate), high (around +40 degrees- hot summer climate), and extreme high (around fire, if possible) temperatures influence on mechanical properties
Sub-task 2. Numerical analysis of moisture permeability and influence on structural properties
Sub-task 3. Recommendation, based on numerical simulation results, will be provided to reach maximal performance of structural elements, depending on application and environment of the new material.

12. Task2. Estimation of environment and temperature impact on the material
Sub-task 1. Numerical estimation of low (around -20 degrees- winter climate), high (around +40 degrees- hot summer climate), and extreme high (around fire, if possible) temperatures influence on mechanical properties
Description:
Here the multi-physical finite element simulations will be done using micro-scale representative volume elements. First of all, the temperature conduction problem will be solved and then temperature field will be applied to structural elements to check their stability and strength. The material mechanical properties (such as Young’s modulus and strength) will be defined as a temperature dependent parameters. As a result it will be possible to estimate the material resistance to extreme climate conditions and give an estimation of structural elements performance.
Necessary INPUT data:
Experimental data on temperature conduction coefficient of selected composite material (from experiments or literature). Data for geopolymer, fibers and aggregates (gravel, stones) are necessary.
Stress-strain curves at selected temperatures
if stress-strain curves are not possible, then materials strength and/or Young’s modulus is necessary

13. Task2. Estimation of environment and temperature impact on the material
Sub-task 2. Numerical analysis of moisture permeability and influence on structural properties
Description:
On the micro-scale the representative volume element should be generated or reused the one from task1. Moisture conduction problem should be solved to estimate the moisture gradients and variation in time. By using computation homogenization method the averaged moisture permeability should be estimated. This result could be used to estimate the structural behavior of beams, frames or slabs depending on moisture environment.
Necessary INPUT data:
Moisture permeability (conduction) coefficients of the selected composites (from experiments or literature)
Material mechanical properties degradation depending on number of freezing-heating cycles

14. Task2. Estimation of environment and temperature impact on the material
Sub-task 3. Recommendation, based on numerical simulation results, will be provided to reach maximal performance of structural elements, depending on application and environment of the new material.
Description:
If possible, the optimal material’s microstructure should be prosed, that include fiber amount, granulometric topology, matrix properties etc.
Figure from: Janis Sliseris, Heiko Andra.Matthias Kabel, Oliver Wirjadi, Brigitte Dix, Burkhard Plinke. Estimation of fiber orientation and fiber bundles of MDF. Materials and Structures, (2016) 49: doi: /s

15. Thank You for attention!