Effects of moisture on aging of polymer composite materials in a cold climate

Abstract

Atmospheric moisture is one of the main climatic factors for polymer composite materials and has the greatest impact on the surface layers of materials. In a cold climate and in seasonal and daily climatic thermal cycling at a transition below 0 °C, the accumulated water in the pores and capillaries of polymeric materials accelerates the appearance of microcracks, their coalescence and the formation of macrodamages in the bulk of the binder and at the boundary with the fibers. The paper presents the results of experiments to study the effect of low temperature on the properties of water-saturated fiberglass with a macrocrack by the method of acoustic emission. Comparative analysis of dried and water-saturated glass fiber laminate samples, containing 0.98% water, showed that for water-saturated samples, acoustic radiation is observed with a pulse amplitude that is more than two orders of magnitude higher than the background. This makes it possible to associate acoustic emission pulses with ice crystallization processes, an increase in internal stresses during the transition of water into ice at the crack tip, and multiple acts of microdamage to the binder generating acoustic pulses. The indicators of the emerging microdamages in the polymer matrix and at the interface between it and the filler are the mean square value of acoustic emission voltage.