Abstract Aluminum/Polytetrafluoroethylene mixtures are currently being studied as reactive material compositions, with focus on shock or impact ignition. In addition, there is an emphasis on increasing the strength of these composites to survive high strain-rate deformation. In this research, an analytical model, based on Eshelby’s approach, and a three-dimensional elastoplastic finite element model were developed along with experimental measurements to investigate the effect of the shape and size of aluminum: spherical particles, whiskers, and fibers, on the strength and stiffness of Aluminum/Polytetrafluoroethylene composites. It was found that the existing surface and size characteristics of aluminum particles (e.g. texturing) play an important role on the mechanical behavior of these composites.