STUDY ON IMPROVEMENT OF MECHANICAL PROPERTIES OF CFRP DUE TO RUBBER MODIFICATION OF EPOXY MATRIX USING SUBMICRON SPHERES

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Firstly, in order to obtain information on improvement of interfacial strength properties between rpoxy eesin and substrate due to rubber modification using submicron CNBR (Cross-linked acrylo Nitrile Butadiene Rubber : 70-100 nm in diameter) spheres, adhesive strenghts of an epoxy resin under Mode I loadings (both static and cyclic) were examined using DCB specimens. The experimental results revealed that The adhesive strength of the epoxy resin became maximum when the CNBR volume fraction was 10%. The interfacial strengths were greatly improved due to CNBR rubber modification under static loading as well as under cyclic loading when the fatigue crack growth rate was relatively high. In both cases, fracture occurred in a cohesive manner while interfacial failure occurred at low crack velocity including near threshold. In this case, the threshold was not improved due to rubber modification.Crabon fabric was used to evaluate the effect of rubber modification of epoxy matrix on strength … More properties of CFRP.The laminates used in the study were fabricated by the hand-lay-up method. Tensile and compressive strenghts under static loading and fatigue strength at several temperatures were measured as well as inter-laminar strength under Mode I loading. The following conclusions were drawn from the experiment. Mode I inter-laminar strength (fracture toughness) is greatly improved due to CNBR modification at a wide range of environmental temperature. It is more than two times higher than that for unmodified cases. Impact strength is also improved while on strength reduction in tension at any test temperature occurs as well as in compression. No reduction in Tg (glassy transition temperature) due to CNBR modification is found as well. That is one of reason for no degradaiton in both tensile and compressive strength properties. CNBR modification of epoxy matrix does not badly affects on the fatigue life of CFRP.Any life reduction was found due to inclusion of submicron spheres of CNBR. Less