Reologie is overal (part 2)

Transcription

1 Reologie is overal (part 2) WND Conferentie, Noordwijkerhout 16, 17 december 2011 Gerrit W.M. Peters

2 three cases case 1: brain tissue (biomechanics) case 2: carnivorous plant (biology) case 3: semi-crystalline polymers (polymer physics)

3 introduction: traumatic brain injury 4/22 large deformation (strain) Traumatic Brain Injury (TBI) often occur during rotational and translational acceleration of the head exact mechanism of TBI still incompletely understood

4 introduction: traumatic brain injury Injury assessment (industry): anthropomorphic test devices (ATD) Head Injury Criterion (HIC)

5 introduction: traumatic brain injury Injury assessment (industry): anthropomorphic test devices (ATD) Head Injury Criterion (HIC) large deformations complex loading paths different deformation modes

6 brain deformations: experiment test device (high speed loading)

7 brain deformations: experiment

8 brain deformations: experiment / simulations

9 brain deformations: experiment / simulations Simulations Experiment Simulations Experiment t = 8 ms t = 12 ms

10 model application Current model Brands et al. model Current model simplified Stress [kpa]

11 model application

12 model application

13 model application

14 brain deformations: protection design

15 three cases case 1: brain tissue (biomechanics) case 2: carnivorous plant (biology) case 3: semi-crystalline polymers (polymer physics)

16 viscoelastic deadly fluid in carnivorous plants Laurence Gaume (Montpelier) & Yoel Forterre (Marseille) the Nepenthes rafflesiana. - Contains a fluid composed of water and polysaccharides

17 a fly tries to flee fluid water

18 influence of concentration - it s not a chemical attack (insects recover when removed from the fluid) -surface tension hardly varies with concentration: ti surface tension doesn t explain (σ fluid = N.m, σ water = N.m). - what other forces are important?

19 drag forces: viscosities of the pure fluid shear viscosity /shear rate (left) transient extensional viscosity / strain (right) arrows indicate typical values corresponding to insect motion in the fluid

20 elongational effects: filament formation dynamical sequence of a fly in the digestive fluid showing a viscoelastic liquid filament attached to its leg (arrows)

21 viscosities: influence of concentration water dilution effect on the shear ( ) and extensional viscosity ( ) (left) dilution effect on the characteristic relaxation time (right)

22 capture rate versus De-number -trapping efficiency is conditioned by both fluid viscoelasticity and insect dynamics - tropical plants, often submitted to high rainfalls and thus variations in fluid concentration. capture rate / Deborah number (flies, ants )

23 three cases case 1: brain tissue (biomechanics) case 2: carnivorous plant (biology) case 3: semi-crystalline polymers (polymer physics)

24 injection molding

25 load-bearing applications of polymers / 25

26 processing of semi-crystalline polymers Polymer processing: high, high p and high structure formation Mechanical behaviour: Influence of morphology 26

27 structure development during flow crystalline amorphous isotropic slightly oriented row shish spherulites spherulites structure kebab 200 μm 1 μm 1 μm 1 μm no orientation flow strong orientation 27

28 in-situ Small Angle X-ray Scattering (SAXS) streak fibrils lobes lamellae

29 in-situ: Small Angle X-ray Scattering (SAXS)

30 processing structure property Injection molding of HDPE 30

31 /processing induced anisotropy processing structure property: example (ipp) static load to failure Factor 400 in lifetime for different positions/directions! 31

32 processing-structure-properties relations

33 processing conditions: injection molding typical cross section of semi-crystalline products A B C y p skin layer shear layer core layer rapid cooling (~100 C s -1 ) flow induced crystallization (~1000 s -1 ) pressure induced crystallization (~1000 bar)

34 modeling flow effects on crystallization

35 nonlinear viscoelasticity: the extended PomPom model

36 non-isothermal quiescent crystallization space filling Schneider rate equations G 3 1 G 2 G 0 1 ( 8 N) ( 4 R ) 2 ( S ) 1 0 tott ( V ) tot tot number radius surface undisturbed volume Avrami equation nucleation density individual growth rate 0 ln 1 real volume NTp, Nmax exp cn T TNref p, exp 2 Gi T p Gmax, i cg, i T TGref, i p

37 flow-induced crystallization total nucleation density N N N tot q f 4 (flow-induced) nucleation rate N f g n hmw 1 shish length (L) growth 1 4 L g l avg for crit rate equations 2 4 f G 1 2 G 0 1 NL length surface undisturbed volume Avrami equation ln real volume

38 numerical simulation: no flow

39 numerical simulation: flow

40 from processing conditions to structure - use the experimental thermal and pressure history in the model and predict the lamellar thickness (distribution) ipp W.J. O Kane, R.J. Young, Journal of Materials Science Letters, 14, (1995)

41 so far for the real problems

42 acknowledgements Tim van Erp Leon Govaert Martin van Drongelen Han Meijer Dario Cavallo Patrick Anderson Luigi Balzano Martien Hulsen Zhe Ma Frank Baaijens Peter Roozemond

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44 high pressure, in situ X-ray SAXS X-ray beam WAXD