Discrete element modeling of the compression molding of polymer–crystal composite particles

Effect of Binder Coatings on the Fracture Behavior of Polymer–Crystal Composite Particles Using the Discrete Element Method

“…The polymer-crystal composite particles were produced by a kneading granulation method (the composite materials were extracted by high-temperature evaporation of the mixed solution and shaped by the kneading machine [46]), in which melamine crystals (C 3 N 6 H 6 ) were coated with fluorine rubber (F2311) binders [47]. Under Carl Zeiss Stemi (Carl Zeiss, Oberkochen, Germany) 508 optical microscope, the morphologies of the composite particles were mainly spherical and rod-shaped, with particle sizes of 0.5 to 3 mm, as shown in Figure 1a.…”

“…The 3D image segmentation was implemented using the open-source software Image J (version 1.46) [48], while the surface mesh was constructed using the commercial platform MATLAB (version 7.0) [49]. More details can be found in our previous study [46]. To quantify the morphological characteristics of the separated composite particle, the principal directions of the particle were first determined by principal component analysis (PCA) [50].…”

“…Figure 6 shows the DEM models of the composite particles with realistic particle shapes, in which the blue balls were binders and the balls of the other color were crystals. The modeling process of the composite particles was amply described in our previous study [46]. To guarantee a better coating effect of the binders, the basic unit size of the binders was smaller than that of the crystals.…”

“…According to the features of the materials, the contact-bond model was applied to the binders and interfaces between binder and crystal, whereas the parallel-bond model was used for the crystals. In our previous study [46], a series of basic mechanical tests was used to determine the DEM parameters of the binders and crystals separately, and the calibration method followed the principle proposed by Gao et al [54]. The determined parameters were then applied to the polymer-crystal composite particles and further validated by single particle crushing tests in experiments and DEM simulations.…”

“…However, the morphology of composite particles has rarely been considered, although it has proved important to the mechanical behavior of particles [35,37,44,45]. During the cold molding of composite particles, the propagation of microcracks and distribution of force chain were investigated [46]. To optimize the cold molding process, it is critical to reveal the microscopic failure mechanism by further exploring the propagation of microcracks and the binder content.…”