Micromechanical Simulation of the Deformation and Fracture of Polymer Blends

Abstract

We couple morphological studies of binary, immiscible blends with mechanical studies of deformation and fracture to determine the influence of the blend composition on the initiation and propagation of cracks in polymeric materials. The Cahn−Hilliard (CH) method is employed to simulate the structural evolution of the molten AB blend. We assume that the material undergoes a rapid quench to yield a solid whose microstructure is given by the CH approach. The output from these CH simulations serves as the input to a dynamic lattice spring model (LSM), a micromechanical model that consists of a three-dimensional network of springs, which connect regularly spaced mass points. Within the LSM, the A and B phases, as well as the interfacial regions, are assigned distinct spring constants, thereby allowing us to model a blend of a compliant and a stiff polymer. With the application of a tensile deformation, the heterogeneous microstructures give rise to complex local elastic fields. Using an energy-based fracture criterion, we selectively remove springs from this system and thereby simulate the initiation and propagation of cracks within the material. By varying the relative stiffness and toughness of the phases, we determine how these characteristics affect the growth of the cracks. We also consider systems where the interface between the different species is mechanically weak, and consequently, fracture occurs through the decohesion of the different polymer domains. In all the systems considered here, we find that “clustering effects”, which are due to interactions between neighboring domains, play a major role in dictating where incipient fracture occurs. Through these studies, we can correlate the complex morphologies within the blend to the mechanical performance of the solid materials.

Mechanical behavior and wrinkling patterns of phase-separated binary polymer blend film

“…where E and v are the Young's modulus and Poisson's ratio, respectively [16][17][18]. At the beginning of simulation, the local force constants are specified at nodal points straddling the boundary between two phases or two nodes according to a series of spring systems weighted by the partial lengths.…”

Enhanced miscibility and strain resistance of blended elastomer/π‐conjugated polymer composites through side chain functionalization towards stretchable electronics

“…Devices with crosslinked polymers demonstrated enhanced thermal stability, resistance to solvents and overall lifetime improvement . Immiscible blends of elastomers and semicrystalline insulators commonly fracture at polymer interfaces, and improved polymer compatibility has been proven to increase cracking resistance . While crosslinking has been studied with insulators and π‐conjugated polymers individually, reactive compatibilization in elastomer/π‐conjugated polymer composites has yet to be reported.…”

“…[33][34][35][36][37][38] Immiscible blends of elastomers and semicrystalline insulators commonly fracture at polymer interfaces, and improved polymer compatibility has been proven to increase cracking resistance. 29,39,40 While crosslinking has been studied with insulators and -conjugated polymers individually, reactive compatibilization in elastomer/ -conjugated polymer composites has yet to be reported. In the following studies, we demonstrate improved compatibility in these blends through side chain functionalization of the -conjugated polymer to regulate morphology and improve mechanical performance.…”

Mechanical properties of high-performance elastomeric nanocomposites: a sequential mesoscale simulation approach

“…For more details related to LSM, see ref. [23][24][25][26]. An important part of this work is the incorporation of linear viscoelastic model into pure elastic LSM.…”