Creep Phenomenon of Simple Composite Structures

Fiber composites which are suitable for low cost engineering applications exhibit remarkable viscoelastic behavior. Therefore creep effect becomes an important consideration in the design of such structures subjected to a sustained load. In order to extrapolate the limited range of creep data, the capability of predicting the creep behavior for a long period is desirable. A "law of mixture" model is proposed for the creep behavior of a unidirectional composite. In the 3-bar truss problem, the stress in each bar and the vertical displacement at the joint are obtained while in the bending problem, the stress expression and the deflection at the mid span of a simple beam are determined based on the Timoshenko beam theory. The results are compared with the case where the members are made of isotropic materials, with and without creep. Finally, the trends of results are examined as certain parameters are varied.