Yoshimichi Fujii

Design of Vinyle-Ester Resin Composite with Affordable Interphase.

In order to develop the new composite material with an additional function, a new concept of affordable interphase has been applied to vinyl-ester resin composite. Fabrication methods of glass woven fabric vinyl-ester resin composite with affordable interphase were proposed and the mechanical properties were investigated. The method using alkyd of an unsaturated polyester resin which has low modulus and high fracture toughness for the resin of affordable interphase was the most appropriate. The alkyd was applied on the glass fabric, and then the laminates were fabricated by hand lay up method using vinyl-ester resin as matrix. Tensile test for the specimens with different interphase conditions was performed and the crack propagation behavior was observed. The tensile strength of the specimen with affordable interphase was higher than that of the specimen without affordable interphase. The strain at which the first transverse cracks observed became higher on the specimen with affordable interphase, because the cracks hardly propagated into high toughness resin area. Consequently it results in the high tensile strength.

Effect of surface treatment condition on interfacial degradation behavior in GFRP under acidic conditions

Interfacial degradation behavior of E-glass cloth reinforced vinyl ester resin under acidic conditions has been investigated. Specimens with different surface treatment conditions were prepared. Mode I fracture toughness tests were performed using DCB specimen, and the effect of surface treatment condition and immersion time on the crack propagation behavior is discussed. The crack propagation behavior changes as a function of the condition of the silane coupling agent and the immersion time due to the degradation of the interphase. A technique is proposed to evaluate the interfacial property. The change of fracture toughness of interphase and resin as a function of immersion time is studied by the crack propagation behavior and the fracture toughness of interphase and resin evaluated by this technique. The fracture toughness of interphase decreases rapidly with immersion in acidic solution.

Estimation of durability of GFRP laminates under stress-corrosive environments using acoustic emission

The objective of this investigation was to estimate the creep life of glass fiber reinforced plastic (GFRP) materials subjected to stress-corrosive environments using acoustic emission (AE). The laminates were fabricated using combinations of rigid bisphenolic polyester resin (LP-1), flexible vinylester resin (R806), random fiber mat and woven cloth. The creep tests were conducted in 5% nitric acid environment. The rigid matrix composites displayed higher AE count rate than the flexible matrix composites. For given creep testing conditions, the woven cloth reinforced specimens displayed higher number of AE counts than the random mat reinforced specimens. The creep life decreased with increasing creep stress, whereas the AE count rate increased with increasing creep stress. A linear relationship was found between the creep life and the AE count rate.