EXPERIMENTAL STUDY ON UNIAXIAL STRAIN CYCLIC CHARACTERISTICS AND RATCHETING BEHAVIOR OF UNSATURATED POLYESTER RESIN

An experimental study was carried out for the cyclic deformation behavior of polyester resin subjected to uniaxial strain or stress-controlled cyclic tension-compression loading. The effect of applied strain amplitude on the strain cyclic characteristics was studied. In the mean time, under the asymmetrical uniaxial stress-controlled cyclic tension-compression loading, the ratcheting behavior of the resin and its dependences upon the applied stress amplitude, mean stress, stress rate and peak stress hold were also discussed. It is shown that the resin is basically a kind of cyclic stable materials, and the responded stress amplitude keeps almost unchanged during the strain-controlled cyclic tension-compression loading. Apparent ratcheting behavior occurs in the resin under the uniaxial asymmetrical stress-controlled cyclic tension-compression loading and the ratcheting strain increases obviously with the increases of the applied stress amplitude, mean stress and the time of peak stress hold, but decreases with the increase of stress rate. The ratcheting of the resin has great time-dependence, which is caused by the significant viscosity of the resin.