Variable Order Fractional Creep Model of Wood Material: Case of Tropical Pericopsis Elata Species

A rheological model based on the new formulation of fractional calculus with variable order is developed to study the viscoelastic behavior of wood. The model, which uses only two rheological elements, exhibits an enhanced memory effect compared to constant-order fractional derivative models, demonstrated by a satisfactory fit to the experimental deformations observed in four-point bending tests on Pericopsis elata samples. By determining the parameters of the linear function of the fractional order used, a physical significance emerges that explains the changes occurring within the material during the tests. This type of model, therefore, provides wood engineers with additional information about the behavior of the material under stress.