Abstract
The objective of this study is to investigate the mechanical properties of fiber reinforced plastics subjected to an arbitrary stress.
To analyze the mechanical properties of FRP mathematically, the author set up a mechanical model composed of four elements; i.e. two springs, one dashpot and one slider. Assuming the material as a visco-plasto-elastic body, these elements were combined in order to give a reasonable explanation for the mechanical behavior of FRP.
Thus, we can express the property of the material by setting up a differential equation regarding stress, strain and the time. If either stress or strain was determined as the function of the time, the other can be mathematically solved and the relation of the stress and the strain can be defined.
Based on the experimental stress-strain diagram of FRP observed at the tensile test of the constant loading velocity, the approximate value of the modulus of the each parameter in the model could be estimated. When the repeated stress was given to the material as the function of the time elapsed, by comparison of the experimental results with the calculated results obtained from the differential equation and by repeating the same operation several times in this way, the accuracy of the estimated moduli could be increased. In this method, the numerical calculation and the automatic graph drawing were operated by the electronic computer.
As the results of this investigation to determine the characteristic equation of FRP, the behavior of the material at the stress which is supposed to occur can be estimated beforehand.
