The authors carried out the experimental works devoted to the problem of describing the processes occurring under long-term loading of composite materials. They studied a glass-reinforced plastic (GP) flat specimen under three-point bending and assumed the deformations normal to the section are purely elastic, and the transverse shear deformation consists of two parts –elastic, and creep deformations and damages formed as a result of accumulation. The authors considered a variant of the creep ratios according to the hardening theory. In previous research authors determined its parameters based on the analysis of the tubular samples operation. It was found that even for thin beams, in contrast to a purely elastic problem, taking into account creep under transverse shear leads to inelastic deflection components that are comparable with their elastic values. The authors presented the results of numerical calculations. It is concluded that at large time and loads, deformations appear in the sample caused by the accumulation of damage.