Machiko Mizoguchi

Effect of fiber surface treatment on mechanical properties of polyethylene / epoxy composites

Tensile and pipe performance tests were carried out on polyethylene/epoxy materials in which the polyethylene fibers were pre-treated to remove the binder and/or sized. The tensile modulus of the composites was increased by pre-treatment, although the tensile strength was almost the same. The knee point stress of the untreated composites decreased on sizing. The strength retention of pre-treated composites was higher than that of composites with both a binder and a size. This difference in pipe performance was caused by the different interphase resulting from pre-treatment and/or sizing.

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.