micromechanics of composite materials
This blog focuses on the micromechanics modeling of composite materials.
research
Characterization of myocardial viscoelastic behavior based on ventricular harmonic motion
Our current ability to accurately measure ventricular global contractile behavior remains unsatisfactory due to the lack of quantitative diagnostic indexes that can assess the mechanical properties of myocardial tissue.
ELASTOMERS
Elastomers, or rubber like materials, have many engineering applications due to their wide availability and low cost. They are also used because of their excellent damping and energy absorption characteristics, flexibility, resiliency, long service life, ability to seal against moisture, heat, and pressure, and non-toxic. It can be easily molded into almost any shape. Applications of elastomers include solid propellant, biomechanics and medical/dental, tires, gaskets, and engine mounts.
A posteriori error estimation (indication) for extended finite element methods (XFEM)
Choose a channel featured in the header of iMechanica
Extended finite element methods (XFEM) have been employed in computational fracture mechanics contexts since their inception in 1999. Although some work has been performed, leading to the first adaptive strategies for the generalised finite element method (GFEM), little or no work has been published on error estimation and adaptive approximations for XFEM. A first attempt at this challenging problem is published here:
Thickness dependent critical strain in Cu films adherent to polymer substrate
For the polymer-supported metal thin films that are finding increasing applications, the critical strain to nucleate microcracks ( εc ) should be more meaningful than the generally measured rupture strain. In this paper, we develop both electrical resistance method and microcrack analyzing method to determine εc of polymer-supported Cu films simply but precisely. Significant thickness dependence has been clearly revealed for εc of the polymer-supported Cu films, i.e., thinner is the film lower is εc . This dependence is suggested to cause by the constraint effect of refining grain size on the dislocation movability.
Finite Element Method for Rubber or Rubber-Like Materials
Hello, I need help for using finite element method in modelling rubber or rubber-like materials?
Thanks in advance
Constitutive Modelling of Elastomers
Rubber or rubber-like materials, or generally elastomers, sustain large elastic deformations. The problems of such cases are non-linear, the non-linearity came from two sources, the first one due to materials, and the second is geomertrical non-linearity. Elastomers are, also, viscoelastic, i.e. time and temperature dependent.
Delamination of stiff islands patterned on stretchable substrates
As another celebration of March Journal Club of Mechanics of Flexible Electronics, this paper has just been submitted.
Abstract
In one design of flexible electronics, thin-film islands of a stiff material are fabricated on a polymeric substrate, and functional materials are grown on these islands. When the substrate is stretched, the deformation is mainly accommodated by the substrate, and the islands and functional materials experience relatively small strains. Experiments have shown that, however, for a given amount of stretch, the islands exceeding a certain size may delaminate from the substrate. We calculate the energy release rate using a combination of finite element method and complex variable method. Our results show that the energy release rate diminishes as the island size or substrate stiffness decreases. Consequently, the critical island size is large when the substrate is compliant. We also obtain an analytical expression for the energy release rate of debonding islands from a very compliant substrate.
viscoelasticity
Elastic stress driven phase inversion
A typical two phase microstructure consists of a topologically continuous `matrix' phase in which islands of `precipitate' phase are embedded. Usually, the matrix phase is also the majority phase in terms of volume fraction. However, sometimes this relationship between the volume fraction and topology is reversed, and this reversal is known as phase inversion. Such a phase inversion can be driven by an elastic moduli mismatch in two-phase solid systems. In this paper (submitted to Philosophical magazine), we show phase inversion, and the effect of the elastic moduli mismatch and elastic anisotropy on such inversion.