• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1241-1250
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• 1996

The characteristics of fatigue cumulative damage and fatigue life of 8-harness satin woven CFRP composites with a circular hole under constant amplitude and 2-level block loading are estimated by Stochastic Makov chain model. It is found in this study that the fatigue damage accumulation behavior is very random and the fatigue damage is accumulated as two regions under constant amplitude fatigue loading. In constant amplitude fatigue loading the predicted mean number of cycles to a specified damage state by Markov chain model shows a good agreement with the test result. The predicted distribution of the fatigue cumulative damage by Markov chain model is similar to the test result. The fatigue life predictions under 2-level block loading by Markov chain model revised are good fitted to the test result more than by 2-parameter Weibull distribution function using percent failure rule.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.193-198
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• 1998

This paper presents the effects of an initial braking velocity, a braking pressure, and the number of braking stop on the tribological behaviors for the three different C-C composites using an inertia dynamic-friction tester. The C-C composites were prepared through the processes of several cycles of pitch impregnation/carbonization with different friction surface texture such as continuous 8-harness satin fabric (ADD-1), chopped fiber (ADD-2) and chopped fiber (ADD-3) having higher fiber volume fraction on friction than ADD-2 by about 10%. ADD-1 exhibited a higher fraction coefficient (0.41~0.33) than those of ADD-2 and ADD-3 (0.32~0.26) under the various initial braking velocities and braking pressures. The fraction coefficients decreased with increasing the initial velocity and the braking pressures. Wear rate by the thickness change after every 25 stop indicated that ADD-2 and ADD-3 having 1.7~2.7 $\mu\textrm{m}$/stop/pair were much lower than that of ADD-1 showing 5.0~6.5 $\mu\textrm{m}$/stop/pair. All specimens showed a little bit lower wear rate during the middle stage than the initial and latter stages among 100 braking stops. ADD-1 showed higher friction coefficient and wear rate due to the active pull-out of the fibers, evidenced by thicker were film and wear debrises.