Contributing Factors of Uneven Climatic Aging for Polymeric Composite Materials: Methods and Modelling

Abstract

Regarding a wide variety of PCMs, the materials’ strength properties which decrease no more than 20% after 30 years of operation are of special interest. One of the important regularities of the climatic aging of PCMs is the formation of gradients of mechanical parameters across the thickness of the plates. The occurrence of gradients must be taken into account when modeling the strength of PCMs for long periods of operation. At present, there is no scientific basis for the reliable prediction of the physical-mechanical characteristics of PCMs for a long period of operation in the world of science. Nevertheless, “climatic qualification” has been a universally recognized practice of substantiating the safe operation of PCMs for various branches of mechanical engineering. In this review, the influence of solar radiation, temperature, and moisture according to gradients of mechanical parameters across the thickness of the PCMs are analyzed according to the data of dynamic mechanical analysis, linear dilatometry, profilometry, acoustic emission, and other methods. In addition, the mechanisms of uneven climatic PCM aging are revealed. Finally, the problems of theoretical modeling of uneven climatic aging of composites are identified.

Strength Characteristics of Carbon Fiber Reinforced Plastic in Shear and Cyclic Extension-Compression after 7 Years of Climate Exposure

“…The results obtained show that the continuous presence of carbon fiber under the influence of climatic factors gives a different effect than moisture saturation-freezing, which simulates the real operating conditions of aircraft structures and reduces its strength characteristics [12,18]. But in both cases, the approach used based on the kinetic concept of fracture, considering the failure process as a set of internal thermodynamic processes, provides new information about the properties of the material [33].…”

“…Plate 3 was exhibited on an open stand at an angle of 45° to the horizon. Due to daily and seasonal fluctuations in air temperature under the influence of solar radiation, the plate was heated to 25 °C and conditions were formed for more intensive moisture transfer (sorption at high humidity and rains and desorption during heating) and the formation of micro-cracks due to different values of the coefficients of linear thermal expansion of the polymer matrix and reinforcing fibers [12]. Under the influence of the ultraviolet component of solar radiation, the destruction of the thin surface layer of plate 3 occurred, over 7 years of climatic tests, and its mass decreased by 0.5 ± 0.05% [16].…”

“…There are examples showing that after 5 years of staying in open climatic conditions, the CFRP decreases the P values by more than 20 % [10,11]. Therefore, measuring the k P values of these materials after prolonged climatic exposure is relevant for practice and elucidation of aging mechanisms [12].…”

“…Figure 3. Dependence of the maximum values of shear stresses in the specimens of plate 1 on time during loading by displacement with rates (mm/s): 0,1 (1, 2); 0,03 (3, 4); 0,01 (5); 0,03 (6); 0,001 (7, 8); 0,0001 (9, 10); 0,0003(11,12) …”

The Initial Stage of Climatic Aging of Basalt-Reinforced and Glass-Reinforced Plastics in Extremely Cold Climates: Regularities

“…These internal stresses contribute to the growth of microcracks, their merging, and the formation of macrodamages. Capillary moisture condenses into these macrodamages, which can turn into a solid phase at temperatures below 0 • C and be a source of additional internal stresses that cause the formation of new damages and cause a decrease in the strength of PCMs [13]. Therefore, it is necessary to monitor indicators characterizing the internal stress gradient, i.e., the elastic modulus and the loss modulus of the solar-and shadow-exposed sides of reinforced plastics.…”