L字型試験片を用いた4点曲げ試験による炭素繊維強化複合材料の層間引張り強度の確率論的評価法

抄録

An interlaminar tensile strength of the CFRP laminates was measured following a test method (ASTM D 6415). L-shape specimens having three different corner curvatures were prepared and loaded by 4 point bending setup. The tested data were analyzed by supposing that the delamination started from a defect where the interfacial stress first exceeded its strength. The defect was assumed a spatial Poisson process. The expected number of the defects in a unit area which were weaker than an interlaminar tensile stress was assumed to follow a power form of the stress. By using the assumption, we were able to find two material properties under the condition that the failure might not occur at the highest stress interface. The probabilistic distributions of the strength based on the present assumption being expressed by maximum interlaminar tensile stress in the specimen and equivalent area calculated considering the nonuniform stress distribution became a Weibull distribution of the maximum interlaminar tensile stress. The experimental results were well agreed by the present probabilistic expression. The probabilistic expression of the interfacial strength is appropriate to assess the interfacial strength problem including volume effects and can be applied to the general interfacial failure problems with nonuniform arbitrary stress states.