this invention relates to composites for use in high temperature elastic composite applications . most particularly , this invention relates to elastic composites formed with a silanol - silanol condensation reaction mixture of silsesquioxane silicone resins thermally stabilized by boron nitride , silica and boron oxide additives as their matrix . the polymer matrix composite comprise a matrix of cured high , intermediate and optionally low molecular weight silicone resins including boron nitride and silica additives and reinforcing material .