Low-Cycle Fatigue Test of FRP Laminate by On-Line Use of a Desk-Top Computer System

Abstract

A desk-top computer (what we call a personal computer) system was on-line used connecting a conventional material testing machine to evaluate the low-cycle fatigue response of glass-mat FRP. During the fatigue test, the strain behavior can be monitored by a large-strain gage put between layers when the specimen is made by the hand lay-up method. As a test result, the fatigue damage of the specimens under high stress levels of 90-75% of the static tensile strength can he characterized by the fact that the ratio of the plastic strain to the total strain increases approximately linearly with the logarithm of the repeated cycle. Using such an information of the computer monitoring, the prediction test of the cycle to failure of the specimen was carried out by on-line use of the computer system. The prediction results were compared with the experimental data. In addition, the fatigue life of the mat FRP in the low-cycle region of less than 200 cycles was evaluated by applying a statistical approach based on the Weibull distribution. The statistical analysis shows that the dispersion of the fatigue life is remarkably large and larger for the higher applied stress level, while the dispersion of the static tensile strength of the specimen is comparatively small.