Experimental study of the contribution of interfacial friction to the deformation resistance of particle-reinforced polymers

A study has been made of the dissipative properties of heavily filled elastomers as influenced by friction of the elastic matrix on the surface of the solid filler particles. In order to model the frictional surface, specimens were predamaged by cyclic deformation, with strain amplitudes sufficient to cause separation of the matrix from the filler. The predeformation operation was performed by means of a mechanical system having individual particle-matrix bonds, so that it was possible to evaluate the contribution of interfacial friction to the resistance of the polymer. When external pressure was applied to the specimens, the width of the hysteresis loop increased with increasing pressure, obviously reflecting an increase of the surface friction in the matrix. It was established that for a given volumetric fill, the dissipation of mechanical energy increased with decreasing particle size (with increasing frictional surface area). The significant influence of interfacial friction on the level and rate of strain relaxation was demonstrated experimentally.Paper presented at the 9th International Conference on the Mechanics of Composite Materials (Riga, October 1995).Translated from Mekhanika Kompositnykh Materialov, Vol. 31, No. 5, pp. 579–583, September–October, 1995.     

Research on the Interfacial Friction in Filled Polymers

A procedure is developed for studying the interfacial friction in filled polymers. The paper presents results of experiments on physical models which represent an elastic matrix contacting with the friction surface. The friction law established experimentally was used to develop computational algorithms describing the processes of cyclic loading and relaxation in filled polymers in the case of permanent contact between the matrix and a hard inclusion and on detachment of the matrix from the inclusion.     

Modelling of mechanical behaviour of damageable particulate composites

A simple discrete structural model has been developed [V.V. Moshev, L.A. Golotina, Non-linear mechanical models for particulate elastometric composites III. Macrocrack initiation from randomly scattered microdamages, Ukrainian Polymer Journal 4(1-2) (1995) 70–84.] for particular composites; it is capable of describing the entire life-cycle of the material from its virgin state through microdamage accumulation to macrofailure. The model geometry corresponds to chain-like cross-sections tied in series where each cross-section represents two clamps interconnected in parallel by a number of elastic links. In extension, some links become ruptured in a random manner reflecting microdamage accumulation which tends to enhance longitudinal stiffness nonuniformity. A stage is reached, when the specimen looses its longitudinal elastic stability. Sudden rupture occurs at the most vulnerable location. The first version of the model was developed for a set of material parameters that were chosen arbitrarily. The phenomena of damage accumulation and macrocrack formation were well represented qualitatively. Examination of random structures of particulate composites and application of a physical discretization approach [V.V. Moshev, O.C. Garishin, Physical discretization approach to evaluation of elastic moduli of highly filled granular composites, Int. J. Solids and Structures 30 (17) (1993) 2347–2355.], however, have suggested the possibility to a further refinement of the model with more realistic structural features. The objective of this work is to provide such a refinement.     

Damage model of elastic rubber particulate composites

A discrete structural model is developed to simulate the behavior of randomly filled rubber particulate composites. Adopted is physical discretization approach for small linear deformations. It is expanded to systems for large elastic deformation that account for structure rearrangement and microdamage accumulation. The life cycle of the material is examined from its virgin state to multiple debonding of matrix from inclusions (primary damages) and growth of microcrack (secondary damages) corresponding to final macrofailure. Both macroscopic (tensile curves) and microscopic (primary and secondary damage accumulation) changes are evaluated for extensional loading. Effective strength characteristics scatter depending on filler concentration is calculated.