A new extrapolation approach was proposed to calculate the strain energy release rates of complex cracks.The point-by-point closed method was used to calculate the closed energy,thus the disadvantage of self-inconsistency in some published papers can be avoided.The disadvantage is that the closed energy is repeatedly calculated: when closed nodal number along radial direction is more than two, the displacement of nodes behind the crack tip that is multiplied by nodal forces, the closed energy has been calculated... A new extrapolation approach was proposed to calculate the strain energy release rates of complex cracks.The point-by-point closed method was used to calculate the closed energy,thus the disadvantage of self-inconsistency in some published papers can be avoided.The disadvantage is that the closed energy is repeatedly calculated: when closed nodal number along radial direction is more than two, the displacement of nodes behind the crack tip that is multiplied by nodal forces, the closed energy has been calculated and the crack surfaces have been closed,and that closed energy of middle point is calculated repeatedly.A DCB(double cantilever beam)specimen was calculated and compared with other theoretical results,it is shown that a better coincidence is obtained. In addition the same results are also obtained for compact tension specimen, three point bend specimen and single edge cracked specimen.In comparison with theoretical results,the error can be limited within 1 per cent. This method can be extended to analyze the fracture of composite laminates with various delamination cracks. |