The role of nano-sized resin fillers on the fracture and viscoelastic behavior of silicones was examined in the context of thermal aging. Systems with different resin volume fractions and resin glass transition temperatures were compared. X-ray scattering patterns were collected over a wide range of q-values in order to provide insight into the physical structure of the silicone elastomers. Additionally, tensile, dynamic mechanical, and fracture tests were performed. Temperature shift factors obtained from the dynamic mechanical data were used to obtain master plots of the fracture toughness as a function of reduced crack velocity. The elastic modulus for each of the materials increased as a function of thermal aging time, and the high-temperature fracture behavior for each of the systems was reduced to values characteristic of unfilled systems after 14 days of aging at 200 degrees C. In order to obtain an accurate representation of the viscoelastic response of the materials in the megahertz frequency regime, quartz crystal resonators were used to measure mass changes and rheological properties after thermal aging. The results are consistent with a simple picture of dynamic heterogeneity, where high toughness requires that regions with different dynamic properties exist within the sample. (C) 2015 Wiley Periodicals, Inc.