Molecular dynamics simulations of polymers can help in understanding the dependence of molecular structure, cross-linking and the chemistry of the polymer chain and resulting thermo-mechanical properties of the polymer. Apart from these thermo-mechanical properties, molecular dynamics is also a powerful tool to examine the durability of polymers with potential aerospace applications under harsh environmental conditions. Ultraviolent radiation from the sun results in dissociation of molecular oxygen into atomic oxygen (AO) which is abundant in lower earth orbit. Testing composites under AO impact requires an extensive experimental setup to simulate low earth orbit (LEO) conditions and is therefore expensive. Using a newly developed accelerated cross-linking methodology in the framework of ReaxFF, bisphenol F and diethyltoluenediamine epoxy polymer chains are manufactured virtually. This simulated polymer is virtually tested for modulus, glass transition temperature, density and is impacted by atomic oxygen at 8 km/s. Thermomechanical properties show good agreement between experiments and simulations. Simulations the polymer during AO impact using ReaxFF provides useful insight to the degradation mechanism in terms of polymer chemistry and thermal profile.