Thermal stress in polymer composites depends on multiple factors. One of the most important is the interfacial adhesion to distribute thermal energy to the matrix with embedded particles or fibres being a conduit for thermal stress distributions.
Other important phase of thermal stress distribution is processing temeprature and cooling rate of the composites; depending on the chemical and physical characteristics of those polymers and fillers, thermal stress can be regulated to achieve the desired result.
Dear Hossein Homayoun, following to Mohini Sain answer, we may take into account the degree oh homogeneity of composite. If so, the nanosize of filler particles will promote the smoothing of distribution of thermal stresses. Along with increasing of strengh (which inherent to nanocomposites) this allow us to improve thermal shock resistance.
On another hand, if the heat resistance of nanocomposites is higher than for usual composites, this competitive factor may expressed in increasing of thermal stress gradient.
So, we must compare these factors. One way for solution of this dilemma is modelling of stress-strained state of the micro- and nanocomposites subjected to thermal shock in the same conditions (equal content of filler and other influencing factors), are n't there? Best regards