The thermodynamics of adhesion interactions in composites based on epoxy resins and Fe and Ni nanoparticles was researched. The enthalpy of dissolution epoxy resins EAF, KDA-1, ED-20 and their composites filled with nanoparticles of Fe and Ni in the whole composition range in toluene were measured using an isothermal calorimetry method. With the help of a thermochemical cycle, the values ??of the mixing enthalpy in a whole range of ratios of resin and metal nanoparticles were calculated. It is shown that the adhesive interaction is accompanied by an exothermic effect. The values ??of the limit adhesion enthalpy on the nanoparticle surface in the saturated layer of composites were calculated. The results were compared with the tensile strength of the cured composites.