Modeling nano-indentation tests of glassy polymers using finite elements with strain gradient plasticity

2005 ◽  
Vol 404 (1-2) ◽  
pp. 179-187 ◽  
Author(s):  
S. Swaddiwudhipong ◽  
L.H. Poh ◽  
J. Hua ◽  
Z.S. Liu ◽  
K.K. Tho
Keyword(s):  
Finite Elements ◽  
Strain Gradient ◽  
Glassy Polymers ◽  
Strain Gradient Plasticity ◽  
Gradient Plasticity ◽  
Nano Indentation ◽  
Indentation Tests

Strain gradient plasticity effect in indentation hardness of polymers

1999 ◽  
Vol 14 (10) ◽  
pp. 4103-4110 ◽  
Author(s):  
Arthur C. M. Chong ◽  
David C. C. Lam
Keyword(s):  
Strain Gradient ◽  
Glassy Polymers ◽  
Strain Gradient Plasticity ◽  
Indentation Hardness ◽  
Gradient Plasticity ◽  
Force Microscopy ◽  
Atomic Force ◽  
Plasticity Effect ◽  
Theoretical Predictions ◽  
Thermosetting Epoxy

Plasticity in material is typically described as a function of strain, but recent observations from torsion and indentation experiments in metals suggested that plasticity is also dependent on strain gradient. The effects of strain gradient on plastic deformation in thermosetting epoxy and polycarbonate thermoplastic were experimentally investigated by nanoindentation and atomic force microscopy in this study. Both thermosetting and thermoplastic polymers exhibited hardening as a result of imposed strain gradients. Strain gradient plasticity theory developed on the basis of a molecular kinking mechanism has predicted strain gradient hardening in polymers. Comparisons made between indentation data and theoretical predictions correlated well. This suggests that strain gradient plasticity in glassy polymers is determined by molecular kinking mechanisms.

Indentation model and strain gradient plasticity law for glassy polymers

1999 ◽  
Vol 14 (9) ◽  
pp. 3784-3788 ◽  
Author(s):  
David C. C. Lam ◽  
Arthur C. M. Chong
Keyword(s):  
Plastic Deformation ◽  
Strain Gradient ◽  
Glassy Polymer ◽  
Glassy Polymers ◽  
Strain Gradient Plasticity ◽  
Molecular Theory ◽  
Indentation Hardness ◽  
Gradient Plasticity ◽  
Strain Gradients

Plastic deformation of metals is generally a function of the strain. Recently, both phenomenological and dislocation-based strain gradient plasticity laws were proposed after strain gradients were experimentally found to affect the plastic deformation of the metal. A strain gradient plasticity law is developed on the basis of molecular theory of yield for glassy polymers. A strain gradient plasticity modulus with temperature and molecular dependence is proposed and related to indentation hardness. The physics of the strain gradient plasticity in glassy polymer is then discussed in relation to the modulus.

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