1 ≤ ϵ ≤ -0.03. click here Figure 3 Mechanical response of bulk PE. (a) Bulk PE under simulated uniaxial tension and compression; and (b) Poisson’s ratio of bulk PE under simulated compression. Simulated compression selleck chemicals llc loading Simulated compression loadings were performed for each of the particles described in ‘Spherical particle molecular models’ section to determine the influence of particle size on the mechanical response. These simulations are similar to the type of compression loads experienced by polymer particles in ACAs when they are compressed between the flat faces of the contacts between the
chip and substrate (Figure 1). The compression was applied to the simulated particles using rigid plates above and below the particles (Figure 4a). Figure 4b shows the dimensions associated with the compression
simulations for a spherical particle of radius R. Figure 4 Applied compression using plate above and below the particles, and dimensions of the compression simulation. (a) Compression of polymer nanoparticle between two flat, rigid surfaces and (b) the dimensions associated with the model. Computational MK-0457 supplier compression tests of the modeled particles are performed by MD as illustrated in Figure 5. Two diamond plates of thickness t = 0.5 nm were placed at both the top and bottom of the particles with a gap of h 0 = 1.0 nm. Constant strain-rate loading was simulated by stepping both the plates towards the particle center, followed by structural relaxation period of 20 ps. Strain rates of 3.125 × 107 s-1 were maintained for all particle sizes by adjusting the step distance of the loading plates (see Table 2).
The temperature of the particles were kept constant by a Nosé-Hoover thermostat at T = 250 K, while the carbon atoms in the loading plates were frozen such that the atoms did not have displacements of any kind except as dictated by the controlled vertical compression. The frozen carbon atoms still maintained the usual non-bonded interactions with the particle Selleckchem Dolutegravir molecules (Table 1). This modeling process is similar to that used for silicon nanospheres . Figure 5 shows the compression of the D 20 particle. Figure 5 Compressed configuration of the D 20 spherical particle. To quantify the simulated response of the polymer particles compressed by a load of P, the nominal strain and nominal stress were defined as, respectively, (1) (2) where h is the loading plate displacement from the initial contact position h 0 (Figure 4b). It is important to note that although these parameters are not strains and stresses according to their classic tensoral definitions , they are used herein as simple scalar measures in a manner consistent with previous studies [5, 6].