EXPERIMENTAL STUDY ON CYCLIC DEFORMATION OF EPOXY RESIN UNDER DIFFERENT AMBIENT TEMPERATURES

Epoxy resin and epoxy-based composite components are frequently subjected to cyclic loading during service. Meanwhile, the ambient temperature usually varies greatly. To ensure the service safety of the structures, it is necessary to investigate the cyclic deformation characteristics of epoxy resin under different temperatures. In this work, a series experiments under uniaxial strain-controlled and stress- controlled cyclic loading were performed on epoxy resin at four temperatures: −20 °C, 25 °C, 55 °C and 85 °C. The characteristic of cyclic softening/hardening, mean stress relaxation and ratchetting were studied under different temperatures, and the influence of temperature on the cyclic deformation behavior of epoxy resin was explored. It was shown that the epoxy resin exhibited cyclic stability during the symmetric strain-controlled cyclic loading, while mean stress relaxation occurred and became more obvious at higher temperatures during the uniaxial asymmetric strain-controlled cyclic loading. Epoxy resin exhibited distinct ratchetting behavior during uniaxial asymmetric stress-controlled cyclic loading. The ratchetting strain consistd of recoverable viscoelastic strain and irrecoverable viscoplastic strain. The ratchetting behavior was suppressed at lower temperatures, while the accumulation of ratchetting strain markedly promoted at higher temperatures. High stress levels also induce more ratchetting deformation. The ratchetting behavior of epoxy resin showed obvious time-dependence and rate-dependence. Ratchetting strain developed more quickly under slower loading rates and with peak holding. As the ambient temperature rised, the loading rate and peak holding time had a more significant impact on the ratchetting of the epoxy resin.