A Visco-Plasto-Elastic Expression for Stress-Strain Diagram of Fiber Reinforced Plastics Subjected to Repeated Loads

Abstract

Fiber reinforced plastics are often used as structural materials at the stress level higher than their elastic limit or proportional limit, since these limits are lower compared with the ultimate strength of the materials. In such case, the stress-strain relation is not linear.
For the purpose of obtaining the non-linear stress-strain relationship mathematically, the author set up a mechanical model which could reasonably express the visco-plasto-elastic properties of FRP.
A simulated fatigue test on this model subjected to sinusoidally repeated stresses was carried out, by means of an electronic computer. By the comparison of the calculated results with the data obtained by the experimental fatigue tests on fiberglass mat reinforced polyester resin laminates, the parameters of the model could be determined, and the specified differential equation for the material, which can be used to express the stress-strain diagram and the rigidity transient caused by fatigue failures, was determined in the concrete.
Thus the mathematical analysis of the mechanical behavior of visco-plasto-elastic materials such as FRP is now possible.