円孔を有する複合材料の引張り‐ねじり２軸組み合わせ静的荷重下における強度

Abstract

The uniaxial tension, pure torsion and tension-torsion biaxially combined static tests were carried out with thin walled cylindrical specimens having a hole. The ‘static notch factor’ was introduced to evaluate the strength of hole notched specimen. The static notch factor is defined as a ratio of the notch strength to the unnotched one. The stress distribution around a hole under biaxially combined load was calculated. The stress concentration was evaluated by the effective stress concentration factor (called the ESCF) in which a multi-axial stress state was considered. The effect of the biaxially loading condition on the static notch factor of hole notched composite was explained by ESCF.The present study gave the following conclusions. The static notch factor has a linear relation with cos(tan-1α), if the biaxially combined stress ratio is denoted as α which is defined as a ratio of two applied nominal stresses σap2/σap6. By using this relation, the static notch factor under biaxially combined load can be empirically predicted by uniaxial tension and pure shear tests. The static notch factor decreased with increasing shear stress component in the applied load, because a small component of shear stress reduces the stress concentration. The static notch factor was analytically predict by means of the minimum strength model (MSM proposed by Tan) with a high accuracy under biaxially combined. This paper also shows that the parameter of the prediction model can be determined by uniaxial tension test.