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Plasticity and fracture in drying colloidal films.
Lucas Goehring1, William J Clegg, Alexander F Routh
1Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077 Göttingen, Germany. lucas.goehring@ds.mpg.de
Physical Review Letters
|February 7, 2013
Summary
Cracks in drying colloidal films exhibit plastic deformation, not just elastic behavior. This suggests that material properties and particle adhesion significantly influence fracture toughness.
Area of Science:
- Materials Science
- Polymer Science
- Soft Matter Physics
Background:
- Colloidal dispersions are widely used in various applications.
- Drying colloidal films are typically modeled using elastic fracture mechanics.
- Elastic models assume linear, elastic, and reversible strains, which may not hold true for all materials.
Purpose of the Study:
- To investigate the validity of elastic fracture mechanics in modeling cracks in drying colloidal films.
- To explore the extent of plastic deformation around crack tips in hard latex films.
- To understand the relationship between yield stress, capillary pressure, and plastic strain in drying films.
Main Methods:
- Experimentally tested hard latex films by intermittently blocking evaporation to relieve stress.
- Analyzed crack tip deformation using atomic force microscopy.
- Developed a scaling argument to relate yield stress to capillary pressure.
Main Results:
- Only 20%-30% of crack opening was relieved upon unloading, indicating significant plastic deformation.
- Atomic force microscopy revealed microcracks and particle rearrangement at crack tips, consistent with plastic deformation.
- Yield stress in drying colloidal films is comparable to maximum capillary pressure, leading to significant plastic strain.
Conclusions:
- Elastic fracture mechanics is insufficient for accurately modeling cracks in drying colloidal films.
- Plastic deformation is a significant factor in the fracture of these materials.
- Film fracture toughness can potentially be enhanced by reducing interparticle adhesion.
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