PTS research activities related to COST FP 1005 Simulation of micro structure mechanics in dynamic fibre networks Timo Kuntzsch, Jan Matheas, Sven Altmann

2  PTS Environmental relevance and sustainability aspects Material testing and expert opinions Education and training Scientific methods Competencies of PTS – all under one roof Efficient use of resources Innovative fibre composites Surface finishing Value chain … – wood – paper – converting – … Scientific methods Design & Simulation Sensorics Analytics

3  PTS Design & Simulation – Focal Points Development of methods and tools for numerical simulation of paper properties Transition from micro- to final product properties micro structure generation micro structure mechanics simulation homogenisation methods Simulation based optimisation of the paper production process considering material and economical criteria Linkage of pulp characteristic, process parameters, paper properties and calculation of costs Maintenance of comprehensive pulp property data base PTS-ProductOptimizer PTS-SoftMcNett H D d d L

4  PTS Micro structure simulation – fibre network generation Making available digital models of single fibres, fibre bonds and fibre networks Fibre arrangement and accumulation Size of modelled section (x-y-plane) Fibre number (~g/m²), morphology, size distribution Fibre orientation distribution und x-y-arrangement Fibre shape profiles in Z-direction after sheet forming Adjustment of sheet thickness and apparent density by pressing process simulation Subsequent modelling of: Behaviour under mechanical load Capillary force driven liquid penetration Optical properties Comparison of different model approaches e.g. shell vs. beam elements fibre network e.g. 2 x 2 x 0,1 mm³

5  PTS Micro structure mechanics simulation Finite element model of fibre bond mechanics Size and shape of bonding areas Mechanical characteristics of fibre bond and fibre wall materials (deformation, failure) Model of fibre network mechanics Search algorithm for contact sites Implementation of fibre bond model Modelling the behaviour under mechanical load (e.g. tensile testing) Deduction of a homogenised material model

6  PTS Example: numerical simulation of tensile testing a) Numerically created paper fibre network (area 1mm², height 0.09, sheet density 0.6g/cm³) b) Mechanical model of the fibre network; centre fibre line, idealised fibre bonds) c) longitudinal fibre forces (network is stretched by 2% in x-direction; tension; pressure) d) bonding forces of idealised fibre bonds in the stretched network

7  PTS Expected benefit from COST FP 1005 Micro structure simulation in fibre networks requires insight in dynamic processes during sheet forming  largely determined by pulp suspension fluid dynamics more realistic and verified micro structure models for improved fibre network mechanics simulation Improved characterisation of physical processes during sheet forming, pressing, and drying, thus more realistic paper and fibre network properties Elucidation of interactions between fibre properties (surface structure, flexibility, morphology …) and suspension flow characteristics Effect of fibre modification on pulp suspension flow characteristics Impact of fluid dynamics on fibre properties during stock preparation treatment Influence of pulp suspension flow parameters on resulting fibre network properties

8  PTS modelling and simulation of paper properties and processes, micro structure simulation, mechanics of fibre networks optimal use and modification of fibres for different processes and products, fibre and fibre network characterization (e.g. fibre morphology distribution …) experimental investigations under conditions very similar to processes in paper mills using the pilot scale paper machine (stock preparation, sheet forming) linking fundamental research to applied research activities Expertise to bring in to COST FP 1005