PSI - Issue 50

S. Lobanov Dmitriy et al. / Procedia Structural Integrity 50 (2023) 163–169 Lobanov Dmitriy S. et al./ Structural Integrity Procedia 00 (2022) 000 – 000

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dependencies of composites elastic and strength properties used in critical structures. Experimental study effect of temperatures influence on the mechanical properties of different classes of polymer composite materials are presented in [Lobanov et al. (2018)]. The study of issues related to the polymer composite materials aging is becoming an important area of research for predicting the service life of structures. Aging of polymer composites is a general problem that leads to deterioration of mechanical properties, reduced design life of the structure, and potential premature, accidental failure. The problem of polymer composites aging in atmosphere was studied in the works [Lobanov et al. (2015), Lobanov et al. (2019) Lobanov et al. (2020)]. Most structures made of polymer composites are exposed to atmospheric factors (temperature, humidity, solar radiation, temperature cycling, tropical and marine climate, etc.) during exploitation, which affect their physical, chemical and mechanical properties. An important task is study of thermal and moisture aging of polymer composites because aging processes can be accelerated with an increase in temperature. Studies of change regularities in the physical and mechanical properties of polymer composites based on glass, carbon and basalt fibers and epoxy, acrylic and polyamide thermoplastic binders during thermal and moisture aging in various environment (distilled water, seawater , machine oil, alkaline solutions, etc.) are reflected in the works of the authors [Lobanov et al. (2015), Nicholas et al. (2016), Amaro et al. (2010)]. The method of joint use of test systems and a system for recording acoustic emission (AE) signals is used in this work to study the effect of thermal aging on the mechanical properties and processes of damage accumulation in fiberglass. The acoustic emission method is based on the elastic waves which registration during deformation and internal local rearrangement in material structure. Waves are recorded on the sample surface with using piezoelectric sensors, then it is are filtered and amplified to extract useful information. Analysis of experimental data allows study the processes associated with the defect’s initiation and propagation in the material structure under a load in real time [Lobanov et al. (2019)]. An analysis of the results of experimental studies of the damage accumulation processes in composite materials using the AE method is presented in modern scientific publications. [Lobanov et al. (2021)]. The authors draw attention to the expediency of using this method for the purpose of experimental study of deformation processes in glass-reinforced plastics. As informative parameters, such as peak amplitudes, signal duration, energy parameter, peak frequency (characteristic of the fast Fourier transform), etc. are often used. [Harizi et al. (2022), Friedrich et al. (2021), Zhao et al. (2022)]. 2. Materials and methods Experimental studies of the change in residual strength properties during interlayer shear of structural fiberglass samples (STEF) at elevated temperatures have been carried out. The tests were carried out with the recommendations of ASTM D2344, in part the geometry of the samples, the loading speed, the geometry of the tooling and the processing of test results. The tests were carried out on the Instron 5982 electromechanical system, which includes a temperature chamber with an operating temperature range from - 100º C to + 350º C. Groups of samples (5 samples per point) of fiberglass were tested at temperatures of 22 º, 70 º, 90 º and 120 º С . A series of experimental studies of the preliminary thermal and moisture aging effects in aggressive environments (machine oil, seawater , process water) of various durations (15, 30, 45 days) and temperatures (22º, 60º and 90º) were also c arried out. To assess the change in strength during interlaminar shear tests on samples of structural fiberglass were carried out. Temperature aging modes and the number of tested samples are shown in Table 1.