Relaxation of non-crystalline solids under mechanical stress

Non-crystalline solids submitted to a thermomechanical stimulus have simila r properties in materials as different as amorphous polymers, molecular, me tallic or oxide glasses. The purpose of the present paper is to give some i nsights into the mechanical response of glassy or liquid media, in relation to their state of disorder. To describe thermomechanical response of non-c rystalline solids, a molecular theory has been developed. We show how the c oncept of quasi-point defects (QPD) introduced in the theory is consistent with small angle X-ray scattering results. The calculations based on the QP D model are also compared to experimental data for various glass-forming sy stems. The magnitudes of the parameters, introduced in the model for these different systems, are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.