Development of a Testing Machine for Determining Fatigue Characteristics of Polymer Composite Materials under Cyclic Bending Loading

Mechanical properties of polymer composite materials are the most important parameters in the development, de-sign and production of products and structures based on them. To determine these properties, various types of tests are performed: static, cyclic (fatigue and crack resistance tests), dynamic. Results of mechanical static tests of PCM do not allow one to obtain information about the mechanism and intensity of a change in their deformation-strength proper-ties under conditions of the product operation, when the structure is affected by cyclically changing loads. This is due to a significant difference in the mechanisms of damage accumulation, emergence and increase in a crack in the PCM under the action of static and cyclic loads. For the evaluation of the intensity of reduction of the deformation-strength properties under the operating conditions, tests are used to determine the fatigue strength of specially made specimens under cyclic loading conditions. The design and the principle of operation of a testing machine for determining the fatigue characteristics of polymer composite materials under the cyclic bending loading conditions are described. The test machine makes possible to determine the change in stress (bending strength) of flat specimens of polymer composite materials with an increase in the number of cycles of three-point bending loading. The registration of stress values is carried out using an S-shaped compression sensor, data of which allows us to plot the dependence of the stress in the specimen on the number of cycles.