This paper presents a testing method of interlaminar strength in the laminated direction of glass cloth reinforced plastics. To obtain the mechanical properties in the laminated direction, a method using the laminated thin wall tube specimens was proposed. The stress distribution in the specimen under tensile load was analyzed by using the finite element method. The shape of the specimen having a flat tensile stress distribution was numerically searched by varying the dimensions of specimen.

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... strain distribution calculated by the finite element method was confirmed by tensile tests of the laminated thin wall tube specimens. The interlaminar strength tests were conducted by subjecting the laminated specimens to axial, torsional and combined loads. The deformation in the laminated direction showed nearly elastic behavior up to the fracture of specimens except the case of compressive deformation. The interlaminar strength of the specimens under combined stress was approximately expressed by Hoffman's fracture criterion.