Many materials, like foams, emulsions, suspensions and granular media obtain finite rigidity once their constituent particles are brought in contact. Nevertheless, all these materials can be made... Show moreMany materials, like foams, emulsions, suspensions and granular media obtain finite rigidity once their constituent particles are brought in contact. Nevertheless, all these materials can be made to flow by the application of relatively small stresses. By varying thermodynamic (temperature or density) and mechanical (applied stress) variables, one can bring about a transition from a freely flowing to a jammed state. What is the elastic response of foams close to the jamming point? How much can these materials be loaded before they flow? What is their behavior like in the bulk? These problems are of great interest in academics, as well as industrial applications (oil/gas extraction, cosmetics, pharmaceuticals and food processes). I study the transition from the flowing to the non-flowing regime in foams and analyze the non-affine behavior at this critical point. Additionally, whereas the usual rheological approach is to study the shear, I have developed a technique to measure compressive response in a real-world, foam system, taking gravity and temperature fluctuations into account. Show less
In this thesis we present a new method to simulate realistic three-dimensional networks of biopolymers under shear. These biopolymer networks are important for the structural functions of cells and... Show moreIn this thesis we present a new method to simulate realistic three-dimensional networks of biopolymers under shear. These biopolymer networks are important for the structural functions of cells and tissues. We use the method to analyze these networks under shear, and consider the elastic modulus, the non-affinity during deformation, the normal modes and the density of states. We expand our analysis to composite networks consisting of stiff and floppy filaments. In the final chapter of the thesis we incorporate the thermal and viscous interactions of the surrounding medium in the calculations, and present the results of the simulations of the shear frequency dependence of the network response. We find that non-affine reorientations are important for understanding the network response. These non-affine reorientations make the networks relatively soft under shear and delay the onset of stiffnening. In composite networks non-affine reorientations allow for an intricate interplay between the stiff and floppy filaments. The frequency-dependent response shows a transition from a soft, non-affine regime at low frequencies to a stiff, close-to-affine response at high frequencies. Show less
