Papers by Author: Takahiko Yoshi

Abstract: Significant stiffness reduction of the plate spring due to delaminations around the interwoven cloths could be prevented by using CFRTP (carbon fiber cloth and Polyethylene Terephthalate (PET)) rather than that by using CFRP (carbon fiber cloth and epoxy), when ultra high cyclic loading was applied to the plate spring under high humidity condition. To explain the result, the prediction model of stiffness reduction was introduced considering time-dependent crack propagation accompanying with creep deformation around the crack tip. Stiffness reduction of CFRP under high humidity condition was not only determined by cyclic crack propagation but also by time-dependent crack propagation accompanying with creep deformation around the crack tip. It was found that CFRTP was effective material of the plate springs on vibration conveyer for the uses under high humidity condition to prevent significant stiffness reduction, where the crack propagation accompanying with creep deformation should be prevented around the crack tip.

Abstract: This paper investigated the stiffness reduction of the plate spring made of CFRP (Carbon cloth and epoxy) subjected to ultra high cyclic fatigue loading under high relative humidity. For practical uses, this paper proposes a new design which prevents the significant degradation with stiffness change of the plate spring at high humidity. Remarkable stiffness reduction of the plate spring due to cracks and delaminations around inter layer could be prevented by using CFRTP rather than that by using CFRP, when ultra high cyclic loading was applied to the plate spring under high humidity condition.