Study of Creep Behavior and a Viscoelastic Model of Bamboo Scrimber under Short-Term Parallel-to-Grain Compression

The creep of bamboo scrimber is an important factor to be considered in engineering applications. Simply using the creep test method not only consumes a lot of time and money, but also cannot be extended to the full stress level. Therefore, in this paper, the short-term creep tests of bamboo scrimber under different stress levels (30% and 40%) and ambient temperatures (30°C–70°C) were carried out. The multicomponent Kelvin-Voigt model and generalized Maxwell shear relaxation model of bamboo scrimber were established. The Maxwell-3 shear relaxation model was used as the constitutive model of bamboo scrimber, and the creep finite-element model of bamboo scrimber under parallel-to-grain compression was established, which verified the creep constitutive model of bamboo scrimber. The results showed that the shear relaxation modulus exhibited a significant decrease during the unstable creep stage, reaching a maximum reduction of 62.0%. It showed nonlinear for the effect of ambient temperature on the compression creep of bamboo scrimber, and the creep rate near the glass transition temperature was significantly higher than that at other temperatures. The fitting coefficients, $R$-square of creep compliance models, were sorted as KV-4 and $\mathrm{KV}\text{-}5>\mathrm{KV}\text{-}3>\mathrm{Burgers}>\mathrm{KV}\text{-}2$. The fitting coefficients, $R$-square of the generalized Maxwell model of shear relaxation modulus, were sorted as Maxwell-4 and $\mathrm{Maxwell}\text{-}3>\mathrm{Maxwell}\text{-}2>\mathrm{Maxwell}\text{-}1$. The simulated creep displacement error of the two specimens was 2.8% and 0.1%, respectively, which verified the accuracy of the numerical simulation method. The paper proposed creep behavior and a constitutive model for bamboo scrimber under parallel-to-grain compression, which holds significant theoretical implications for its widespread application.