To the estimation of sample fatigue from polymer composite materials | Mekhanika | kompozitsionnykh | materialov i konstruktsii
> Volume 22 > №3 / 2017 / Pages: 329-341

To the estimation of sample fatigue from polymer composite materials

,

Abstract:

The complexity of the internal structure of composite materials results in a variety of forms of fatigue damage in them, each of which individually or in combination with other contributes to the carrying capacity of the non-metallic products.. The variety of forms of fatigue damage in composite materials products and their development are not allowed so far to form a composite material commonly accepted laws such as the law of Paris, the linear summation of Minera and others. In the paper the option of detecting emerging fatigue damage to the sample and its further development through the study of the fall of his natural vibration frequency is considered. For this the experimental researches of fatigue strength of cantilever-fastened specimens of CFRP in fatigue tests them by first bending form are carried out. It is recommended to account that sample has exhausted its carrying capacity, if his natural vibration frequency decreased to an acceptable value, which is determined from the analysis of the frequency chart Campbell. In this work five percent are taken for an acceptable value of the decreasing of the natural vibration frequency. After the fatigue testing of samples, natural frequency of which had decreased on five percent, the additional studies were conducted to determine their residual strength and stiffness at three-point bending and residual shear strength. The manner of samples preparing for static tests is described. Analysis of residual flexural strength is performed. The correlation connections between the decreasing of the natural vibration frequency and the characteristics of residual strength and stiffness are established. The researches of specimen residual strength and stiffness are shown that the five percent permissible value of the natural vibration frequency drop is a conservative assessment of the carrying capacity of the product.

0