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outstanding problems in the physics of deformation of polymers. Han E.H. Meijer and Leon E. Govaert. Dutch Polymer Institute (DPI) Materials Technology (MaTe) Eindhoven University of Technology (TU/e) APST ONE, Advances in Polymer Science and Technology
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outstanding problems in the physics of deformation of polymers Han E.H. Meijer and Leon E. Govaert Dutch Polymer Institute (DPI) Materials Technology (MaTe) Eindhoven University of Technology (TU/e) APST ONE, Advances in Polymer Science and Technology July 8 – July 10, 2009, Johannes Kepler University Linz, Austria
introduction • predicting performance of present models • outstanding problems: • first question: origin of deformation kinetics • second question: origin of ageing kinetics • third question: origin of strain hardening • summary
localization of strain tough brittle • PC: necking • moderate localization • stable growth • PS: crazing • extreme localization • unstable growth
a comment on (solid state) rheology rheology: branch of fluid mechanics call themselves non-Newtonian but are Newton’s successors that are mathematically well educated and only deal with transient homogeneous shear flows it took them 50 years to arrive at a constitutive equation that is also valid in transient homogeneous extensional flows solid state rheology: branch of solid mechanics Hooke’s successors that necessarily have to deal only with transient inhomogeneous extensional flows
rejuvenation polystyrene PS
ageing mechanically rejuvenated moderate ageing severe ageing unstable localisation homogeneous deformation stable localisation brittle ductile ductile
from compression to tension compression entanglement network intermolecular total ageing = + Mn
from compression to tension compression entanglement network intermolecular total ageing = + Mn tension increasing entanglement density
introduction • predicting performance of present models • outstanding problems: • first question: origin of deformation kinetics • second question: origin of ageing kinetics • third question: origin of strain hardening • summary
from compression to tension compression
from compression to tension compression tension
from compression to tension compression fit tension prediction
indentation and scratching indentor type round a c a Berkovich b b flat punch c
indentation and scratching flat-ended cone angle: 60o diameter: 10.0 µm post-mortem visco-elastic visco-plastic
indentation and scratching line: experiment symbol: prediction flat-ended cone angle: 60o diameter: 10.0 µm post-mortem visco-elastic visco-plastic
indentation and scratching results are quantitative lines: experiments symbols: predictions ageing deformation rate ageing kinetics deformation kinetics
indentation and scratching strategy hybrid experimental/numerical method Fn v Ff polymer Ff experiments Fadh= Ff- Fdef ? simulations Fdef T,v,scale effects
indentation and scratching results: experimental: influence sliding velocity
indentation and scratching results: numerical: deformation only Fn=300mN v =0.1µm/s r =50 µm visco-elastic visco-plastic
indentation and scratching results: experimental versus numerical deformation only Fadh Fdef Ff = Fdef + Fadh
indentation and scratching results: numerical: influence interaction between indenter and polymer what about adhesion? most basic dry-friction model: Leonardo da Vinci (1452) Amonton (1699) - Coulomb (1781) stick: slip :
indentation and scratching results: numerical: influence interaction between indenter and polymer
indentation and scratching results: numerical: influence interaction between indenter and polymer Fn vx Ff A2 polymer Fsim A1 Ff = Fsim = Fdef Fadh = 0
indentation and scratching results: numerical: influence interaction between indenter and polymer Fn vx Ff A2 polymer Fsim A1 Ff = Fsim = Fdef + Fadh Fadh Fdef
indentation and scratching results: numerical: influence interaction between indenter and polymer Fn vx Ff A2 polymer Fsim A1 Ff = Fsim = Fdef + Fadh Fadh Fdef
indentation and scratching results: numerical: influence interaction between indenter and polymer
indentation and scratching results: experimental versus numerical validation using different tip Fn=150mN v =0.1µm/s r =10µm visco-elastic visco-plastic
indentation and scratching results: experimental versus numerical validation using different tip
indentation and scratching results: experimental versus numerical wear
introduction • predicting performance of present models • outstanding problems: • first question: origin of deformation kinetics • second question: origin of ageing kinetics • third question: origin of strain hardening • summary
introduction • predicting performance of present models • outstanding problems: • first question: origin of deformation kinetics • second question: origin of ageing kinetics • third question: origin of strain hardening • summary
deformation kinetics rate dependence of PC
deformation kinetics rate dependence of PC
constant stress . deformation kinetics constant strain rate response rate-dependent yield failure under constant strain rate and constant stress experiment governed by same kinetics
deformation kinetics time-dependent accumulation of plastic strain: plastic flow
deformation kinetics influence of thermal history on intrinsic behavior influence of thermal history on rate dependence
deformation kinetics and time to failure PC influence of thermal history on intrinsic behavior influence of thermal history on time-to-failure
deformation kinetics and time to failure strain rate dependence of yield stress stress dependence of time-to-failure
deformation kinetics and time to failure question 1: how does molecular architecture determine deformation kinetics
deformation kinetics and time to failure question 1: how does molecular architecture determine deformation kinetics and thus the long term behaviour asreflected in the time-to-failure
introduction • predicting performance of present models • outstanding problems: • first question: origin of deformation kinetics • second question: origin of ageing kinetics • third question: origin of strain hardening • summary
ageing and ageing kinetics ageing ageing influence of thermal history on intrinsic behaviour influence of thermal history on rate dependence
ageing and ageing kinetics PS PS: brittle fracture within hours PC: necking returns within months
ageing and ageing kinetics ageing accelerated by temperature Arrhenius temperature dependence; ΔH 205 kJ/mol
ageing and ageing kinetics ageing accelerated by stress
ageing and ageing kinetics rate dependence of yield stress aged loading curve changes in thermal history captured by a single state parameter: Sa behaviour independent of molecular weight distribution
ageing and ageing kinetics yield stress increases with time
ageing kinetics: two domains temperature history received during processing temperature history received during product life • ~seconds • high temperatures • fast evolution • ~years • low temperatures • slow evolution evolution of yield stress in both domains governed by the same kinetics