(360bf) Coarse-Grained Models of Polyetherketoneketone (PEKK) Used to Perform Fusion Weld Simulations and Predict Resulting Mechanical Properties.

Carbon fiber composites with a thermoplastic matrix offer manufacturing advantages over thermoset-based composites, particularly in terms of high-throughput production through fusion welding of initially separate parts. With this approach, chain diffusion and entanglement across an interface are the primary load bearing mechanisms as opposed to mechanical fasteners or adhesives. Therefore, understanding the atomistic details of polymer diffusion during fusion welding is central for understanding how processing influences structure and how that ultimately impacts mechanical strength. Molecular simulations offer insight into these details, but the long time scales relevant to polymer relaxation, entanglement, and diffusion are challenging to access. Here we implement the multi-state iterative Boltzmann inversion (MSIBI) method of coarse-graining and develop a transferable MSIBI python package to generate coarse-grained potentials for the thermoplastic matrix polymer polyetherketoneketone (PEKK). Fusion bonding simulations of PEKK are performed over a range of bulk polymer preparations and system sizes. This workflow for modeling fusion welding leverages the MoSDeF.org ecosystem of simulation tools, particularly mBuild, foyer, HOOMD-Blue and signac.