No abstract

The influence of monomer functionality on the mechanical properties of epoxies is studied using molecular dynamics (MD) with the Reax Force Field (ReaxFF). From deformation simulations, the Young's modulus, yield point, and Poisson's ratio are calculated and analyzed. Comparison between the network structures of distinct epoxies is further advanced by the monomeric degree index (MDI). Experimental validation demonstrates the MD results correctly predict the relationship in Young's moduli. Therefore, ReaxFF is confirmed to be a useful tool for studying the mechanical behavior of epoxies. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 255–264

No abstract

To date, molecular modeling of cross-linking polymers has focused on those involving single-reaction cure mechanisms, such as epoxies and the epoxide–amine reaction. In this work, we have developed a novel cross-linking framework that is capable of undertaking complex cure mechanisms involving several simultaneous reaction pathways with minimal user input. As a case study, a bismaleimide (BMI) resin is considered herein which possesses multiple cure reactions and reaction pathways. Using an adaptable molecular dynamics simulation method, we highlight our framework by implementing five distinct cure reactions of Matrimid-5292 (a BMI resin) and predicting the corresponding thermomechanical properties. The method is used to establish the influence of different cure reactions and extent of curing on mass density, glass transition temperature, coefficient of thermal expansion, elastic moduli, and thermal conductivity. The developed method is further validated by comparison of these properties to experimentally observed trends.

Polyether ether ketone (PEEK) is a high-performance, semi-crystalline thermoplastic that is used in a wide range of engineering applications, including some structural components of aircraft. The design of new PEEK-based materials requires a precise understanding of the multiscale structure and behavior of semi-crystalline PEEK. Molecular Dynamics (MD) modeling can efficiently predict bulk-level properties of single phase polymers, and micromechanics can be used to homogenize those phases based on the overall polymer microstructure. In this study, MD modeling was used to predict the mechanical properties of the amorphous and crystalline phases of PEEK. The hierarchical microstructure of PEEK, which combines the aforementioned phases, was modeled using a multiscale modeling approach facilitated by NASA's MSGMC. The bulk mechanical properties of semi-crystalline PEEK predicted using MD modeling and MSGMC agree well with vendor data, thus validating the multiscale modeling approach.