Designation of Mode Mix in Orthotropic Composite Delamination Problems

In interfacial fracture modeling of composite delamination, mode mix is typically specified in terms of energy release rates. Other near-tip quantities can be used to designate mode mix, however. This paper considers the designation of mode mix in terms of energy release rates, stress intensity factors, stresses ahead of the crack tip and crack face displacements and the consequences of using different near-crack-tip quantities to designate mode mix in analyzing composite delamination. The problem addressed is two-dimensional debonding between plies or ply groups modeled as in-plane orthotropic materials; however, the conclusions discussed apply to general composite delamination problems. It is shown that use of different quantities to designate mode mix can give significantly different results in matching composite applications to mixed-mode toughness tests. For cases where measured interfacial toughness increases with increasing mode II deformation, it is demonstrated that use of a mode mix designation based on energy release rates could be non-conservative. Based on these findings, it is suggested that practitioners consider the differences in failure load predictions that would result if different near-tip quantities were used to relate composite applications to measured toughnesses. To this end, methods for converting mode mix designations in terms of energy release rates into designations in terms of other fracture quantities are outlined and applied.

[1]  M. Manoharan,et al.  Strain Energy Release Rates of an Interfacial Crack Between Two Orthotropic Solids , 1989 .

[2]  T. O'Brien.  Characterization of delamination onset and growth in a composite laminate , 1982 .

[3]  Zhigang Suo,et al.  Singularities, interfaces and cracks in dissimilar anisotropic media , 1990, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[4]  P. G. Charalambides,et al.  An energy method for calculating the stress intensities in orthotropic bimaterial fracture , 1996 .

[5]  Carl T. Herakovich,et al.  Composite Laminates with Negative Through-the-Thickness Poisson's Ratios , 1984 .

[6]  Z. Suo,et al.  Mixed mode cracking in layered materials , 1991 .

[7]  James R. Reeder,et al.  A Bilinear Failure Criterion for Mixed-Mode Delamination , 1993 .

[8]  M. Kanninen,et al.  A finite element calculation of stress intensity factors by a modified crack closure integral , 1977 .

[9]  Z. Suo,et al.  Interface crack between two elastic layers , 1990 .

[10]  Fu-Kuo Chang,et al.  Matrix Cracking and Delamination in Laminated Composite Beams Subjected to a Transverse Concentrated Line Load , 1993 .

[11]  Deng Xiaomin.  An asymptotic analysis of stationary and moving cracks with frictional contact along bimaterial interfaces and in homogeneous solids , 1994 .

[12]  P. D. Mangalgiri,et al.  Influence of the resin on interlaminar mixed-mode fracture , 1987 .

[13]  I. S. Raju,et al.  Computation of strain energy release rates for skin-stiffener debonds modeled with plate elements , 1993 .

[14]  B. Davidson.  Prediction of Energy Release Rate for Edge Delamination Using a Crack Tip Element Approach , 1995 .

[15]  C. Sun,et al.  Influence of Ply Orientation on Delamination in Composite Laminates , 1996, Aerospace.

[16]  J. Qu,et al.  Interfacial fracture mechanics for anisotropic bimaterials , 1993 .

[17]  James R. Rice,et al.  Elastic Fracture Mechanics Concepts for Interfacial Cracks , 1988 .

[18]  John W. Hutchinson,et al.  Crack Paralleling an Interface Between Dissimilar Materials , 1987 .

[19]  T. O’Brien,et al.  Local Delamination in Laminates with Angle Ply Matrix Cracks: Part 2. Delamination Fracture Analysis and Fatigue Characterization , 1993 .

[20]  Anthony M. Waas,et al.  Energy-Based Mechanical Model for Mixed Mode Failure of Laminated Composites , 1995 .

[21]  Jack Beuth,et al.  Separation of crack extension modes in orthotropic delamination models , 1996 .

[22]  A. Evans,et al.  A Test Specimen for Determining the Fracture Resistance of Bimaterial Interfaces , 1989 .

[23]  R. McMeeking,et al.  A method for calculating stress intensities in bimaterial fracture , 1989 .

[24]  Y. Mai,et al.  Mixed-Mode Fracture of Adhesively Bonded CF/Epoxy Composite Joints , 1996 .