Experimental study of the influence of preliminary complex mechanical loads on the deformation and strength properties of polymer composites

Abstract

The paper discusses the issues of complex cyclic and low-speed impact loads on the strength and deformation properties of polymer composites. The results of experimental study of the influence of preliminary cyclic loads on the residual properties of samples of layered-fibrous composite materials under various layouts and loading modes are presented. Experiments were carried out using the research facilities of the Center for Experimental Mechanics (http://www.ckp-rf.ru/ckp/353547/). As part of the work, a series of tests was performed on fiberglass composite samples made with three types of laying the reinforcement layers [0/90], [±45], [0/30/0/60]. For each type of samples static strength and stiffness properties were determined. Fatigue tests were performed at the same level of maximum stress in the cycle, frequency and asymmetry coefficient. The dependences of the change in the residual strength properties of layered fibrous composites are presented in the form of fatigue sensitivity diagrams. For samples with layouts [0/90], [0/30/0/60], a staging change in relative residual static strength was noted. For the studies materials, areas of initial fatigue sensitivity, stabilization and exacerbation of fatigue sensitivity were revealed. The research of the regularities of changes in stiffness and strength properties of polymer composite materials (PCM) in the process of fatigue accumulation of damage at various stress levels of cyclic loads was conducted for samples with reinforcement angles [0/90]. The test results are presented in the form of diagrams of changes in the residual strength and stiffness properties of fiberglass samples. For the fiberglass specimens, in this range of loads, the dependences were non-linear and had a similar pattern of change. The results of the study of the influence of preliminary low-velocity impact of varying intensity on the residual mechanical characteristics of the sample plates of carbon-fiber composite materials with spatial reinforcement schemes are presented. As a result, it was noted that the additional preliminary shock reduces the residual strength, however, when failure, the stage of postcritical deformation is realized.