Cyclic strength of polyester acrylate composites

Abstract

The results of a study of the cyclic strength of polyester-racrylate composites are presented. The mechanical properties of the samples were determined on a Shimadzu Autograph AG-X Series universal testing machine. Test process management and pre-processing of data obtained on this machine are performed using the TRAPEZIUM X * 1 software. The measurements were carried out with a constant velocity of movement of the active capture of 3 mm / min. The compression force was directed along the long axis of the sample. The cyclic mechanical impact on the sample was carried out according to the following scheme: “loading to a certain maximum stress σmax in a given cycle → complete unloading at the same speed → five times repeating the cycle with a given load σmax → repeating the five times cycling procedure with a stepwise change in maximum load σmax until the sample is destroyed. It is shown that a characteristic feature of the load – strain curves during cycling is the presence of hysteresis, which is especially significant in the first cycle. The first compressive loading of the sample leads to significant changes in the structure of PEA. In the second and subsequent cycles, the difference between the loading and unloading curves of the sample is noticeably smaller and depends little on the cycle number. Then the state of the sample is stabilized, and subsequent cycling affects it much weaker. It is characteristic that the maximum difference between the losses in the first and subsequent cycles is observed at the minimum initial voltage. At maximum loads, the unloading curve is steeper than the loading curve, and at low loads, vice versa. Hysteresis losses increase with increasing maximum load in the cycle, which corresponds to an increase in the contribution of the plastic component to the total deformation of the sample. The E (σ) dependences obtained during loading in the first cycle practically coincide with the loss curves. In subsequent cycles, a slight quantitative change in these curves is observed without changing their general nature. The dependences obtained by unloading the samples are fundamentally different from the dependences obtained by loading. In this case, the discrepancy between the E (σ) curves during loading and unloading in the composite is slightly weaker than in pure PEA.