The effect of cell-size, cross-linking ratio, and force fields on the determination of properties of epoxy crosslinked by heuristic protocol

Abstract

This research explores the effect of the cell size, cross-linking ratio, and the force fields used in the molecular dynamic simulation for determining the mechanical and thermal properties of cross-linked epoxy formed with a heuristic cross-linking procedure. The effects of the abovementioned variables on density, Young’s modulus, shear modulus, bulk modulus, and glass transition temperature values by molecular dynamics (MD) simulation were evaluated. Epoxy resin diglycidyl ether of bisphenol A and hardener diethyl toluene diamine were used in modeling the epoxy. A Heuristic method for reactive molecular dynamics (REACTER) protocol was used as the cross-linking procedure. Firstly, six structure cells were prepared in different cell sizes with a crosslinking ratio of 75%, and a mechanical analysis of all cells was performed. Then, the largest cell was prepared for three different crosslink ratios and its mechanical and thermal properties were calculated. Finally, the mechanical properties of the largest cell were calculated using the three different force fields namely the COMPASS, DREIDING, and UNIVERSAL. The results were also compared with the molecular dynamic simulation results performed using the other crosslinking procedures, and experimental results available in the literature. In comparison, it was observed that the results obtained with MD simulations coincided with the experimental data. It has been concluded that using the largest cell gives closer results to the experimental data but the processing time is also increasing rapidly. Moreover, it was also observed that the increase in the crosslinking ratio caused an increase in the mechanical properties of the epoxy and a significant increase in the glass transition temperature. Finally, compared to other force fields, it is seen that the mechanical analysis results obtained with the COMPASS force field comply more with the experimental data.

Optimal Molecular Dynamics System Size for Increased Precision and Efficiency for Epoxy Materials

“…As the number of atoms increases, the standard deviation significantly decreases at 15,000 atoms, after which the standard deviation values stabilize. A similar trend was observed by Erdol et al and Deng and Du. , The absolute values of the Young’s modulus do not show a statistically significant variation with the system size and show statistical agreement with the experimental values. The simulation time shows a roughly linear increase with the system size.…”

“…Several studies have focused on addressing MD model size in simulations of polymer/amorphous materials. ,,− Deng and Du developed a series of MD models for sodium borosilicate glasses to determine the effect of MD system size on the predicted physical and mechanical properties. System sizes ranging from 320 to 25,600 atoms were simulated, with the precision converging for systems with 1600 atoms.…”

“…System sizes ranging from 320 to 25,600 atoms were simulated, with the precision converging for systems with 1600 atoms. Erdol et al 14 examined the effect of cell size on the tensile and shear modulus of epoxy ranging from 936 to 29,952 atoms using three different force fields. They demonstrated that the effect of the simulation cell size on the standard deviation of predicted properties reduces as the model size increases above 3744 atoms.…”

Investigation of Young's modulus of defective graphene‐reinforced epoxy at different weight ratios by molecular dynamics

“…[19][20][21][22] The molecular dynamics (MD) simulation method is used to predict the properties of these new-generation nanocomposite materials because manufacturing them is challenging, expensive, and time-consuming. [23][24][25][26][27][28][29][30][31] The pioneering work by Alder and Wainwright introduced the employment of the MD methodology, which involves the molecular-level modeling of materials and the simulation of atomic motions under predefined ambient conditions. 32 Afterward, Rahman advanced the field using the MD method to simulate argon fluid, with Lennard-Jones potentials serving as interatomic interactions.…”

“…The manufacturability and production processes of nano‐composite materials containing graphene and epoxy are also separate research areas 19–22 . The molecular dynamics (MD) simulation method is used to predict the properties of these new‐generation nano‐composite materials because manufacturing them is challenging, expensive, and time‐consuming 23–31 . The pioneering work by Alder and Wainwright introduced the employment of the MD methodology, which involves the molecular‐level modeling of materials and the simulation of atomic motions under predefined ambient conditions 32 .…”