The dynamics of rods or fibers such as those in toothbrushes, disposable diapers, and fiber-reinforced plastic have not yet been modeled because of the complexity of their nonlinear deformations and the multiple contacts among fibers. To simulate the behavior of the fibers, we developed a partially flexible rod model using some connected particles based on the discrete element method. To validate the model, we performed deflection tests for a cantilever beam and fixed hinged beam, along with a vibration test for the cantilever beam. The developed model showed good agreement with other approaches such as nonlinear beam deflection theory and the finite element method. (C) 2013 Elsevier B.V. All rights reserved.