The methods of control of strain-strength characteristics of polymeric composite materials based on prescriptions are well known and are widely practiced. We discuss a new method in formation of such characteristics. The method consists in inputting of microdefects (mesodefects) into the polymer matrix; this allow us to replace the spikes of stresses around the hard inclusions, which become the stress concentrators, by a set of stresses oscillating at relatively small amplitude. This can help us to improve elastic characteristics of composites.