This paper evaluates interfacial failure criterion under combined stress state and precise location along the fi ber circumference of interfacial failure (debonding) initiation at glass fi ber fi ber/ epoxyinterfacebythecruciform specimen method.Theeff ects ofboth thermalresidualstress occurred during specimen preparation and inelastic stress-strain constitutive relationship ofmatrix resin on the evaluation of interfacial failure criterion are considered. The interfacial stresses distribute

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... g with fi ber circumference. In this study, the location of interfacial failure initiation is specifi ed and the interfacial failure criterion is evaluated. By changing the cruciform arm angle (theanglebetween thefi berand theloading directions),variouscombined stressstatesareobtained which makeit possibleto evaluatetheinterfacialfailurecriterion.Both thequadraticand parabolic criteria are assumed and discussed.