PSI - Issue 18

Lobanov Dmitriy S. et al. / Procedia Structural Integrity 18 (2019) 347–352 Lobanov Dmitriy S. et al./ Structural Integrity Procedia 00 (2019) 000–000

351

5

3.2. AE processing In the course of analyzing the AE data the diagrams of the dependence of cumulative energy for all groups of samples were plotted. These graphs are presented in Figure 5. The cumulative energy was calculated as the total energy of the AE over all time intervals.

0,0002

0,00016

0 Cumulative energy, V 2 s 0,00004 0,00008 0,00012

0 Cumulative energy, V 2 s 0,00005 0,0001 0,00015

normal 120/5 160/5 200/5

normal 160/15 200/15

0,00 45,00 90,00 135,00 180,00

0,00 45,00 90,00 135,00 180,00

Time, s

Time, s

After 5 days After 15 days Fig. 5. Diagrams of dependences of the cumulative AE energy for samples without thermal exposure (normal), after 5 days exposure (а), after 15 days exposure (b) It should be noted that the higher the temperature of exposure in groups of samples after 5 days and after 15 days the higher the value of the cumulative energy. Cumulative energy graphs reflect the degree of accumulation of defects in the material. It is also noted that in groups of samples aged for 15 days the process of growth of cumulative energy began earlier than for a group of samples after 5 days. This also confirms that as a result of the temperature aging the mechanical properties of the composite are degraded, the growth of defective structures, the embrittlement of the matrix and the destruction of the fiber were occur. Conclusions In the course of the work, tensile tests of structural fiberglass samples were conducted to study the effect of temperature aging on the mechanical properties of this material. Additionally, the AE method was used to study the process of damage accumulation and destruction under the action of a load. As a result, the mechanical characteristics of fiberglass, such as the elastic modulus and strength, are determined. The dependence of these characteristics on various modes and duration of temperature exposure is revealed. The analysis of the surface fractures of the samples was occurred. A change in the color and structure of the composite is noted, and the degradation of the mechanical characteristics is also obvious. The graphs of the cumulative AE energy were plotted and analyzed. There is a correlation between the level of cumulative energy and temperature aging modes. Thus, increasing the temperature at which the samples were thermal exposed and the duration of exposure means an increase in the level of cumulative energy.