RESEARCHES ON STRESS-INTENSITY FACTORS OF ORTHOTROPlC PURE BENDING BEAM

Based on the theory of linear-elastic fracture mechanics,the crack tip stress field of orthotropic plate is still controlled by the stress-intensity factors,therefore to study the stress-intensity factors of orthotropic plate is an important problem in studying the fracture of composite materials.At present,not a few papers calculate the stress-intensity factors by finite element theory,but few by testing technique.With composite material fracture theory,the paper derives the relation formulas between the K_I、K_Ⅱ and the v displacement with different fiberreinforced directions.In this paper,the glass fiber-reinforced orthotropic plate is worked into the pure bending beam with a unilateral cutonit,which is tested by using the sticking film moue interferometry.Through testing,the full-field displacement of the moire pattern is given,the K_I and K_Ⅱ values are further calculated from the displacement in the crack-tip.The patterns that the pure bending beam has different crack lengthes and is in different fiber-reinforced directions are given in this paper.Being exposed twice,the grating density of the moire pattern can reach 1260 line/mm.At the same time,the same specimen is calculated by using SAP-84 plate clement program on microcomputer for inspecting the testing precision.At last,the test results are compared with the calculating ones in error.