Fracture criterion for kinking cracks in a tri-material adhesively bonded joint under mixed mode loading

Abstract The fracture behavior of a composite/adhesive/steel bonded joint was investigated by using double cantilever beam specimens. A starter crack is embedded at the steel/adhesive interface by inserting Teflon tape. The composite adherend is a random carbon fiber reinforced vinyl ester resin composite while the other adherend is cold rolled steel. The adhesive is a one-part epoxy that is heat cured. The Fernlund–Spelt mixed mode loading fixture was employed to generate five different mode mixities. Due to the dissimilar adherends, crack turning into the adhesive (or crack kinking) associated with joint failure, was observed. The bulk fracture toughness of the adhesive was measured separately by using standard compact tension specimens. The strain energy release rates for kinking cracks at the critical loads were calculated by a commercial finite element analysis software ABAQUS in conjunction with the virtual crack closure technique. Two fracture criteria related to strain energy release rates were examined. These are (1) maximum energy release rate criterion (Gmax) and, (2) mode I facture criterion (GII = 0). They are shown to be equivalent in this study. That is, crack kinking takes place at the angle close to maximum G or GI (also minimum GII, with a value that is approximately zero). The average value of GIC obtained from bulk adhesive tests using compact tension specimens is shown to be an accurate indicator of the mode I fracture toughness of the kinking cracks within the adhesive layer. It is concluded that the crack in tri-material adhesively bonded joint tends to initiate into the adhesive along a path that promotes failure in pure mode I, locally.

[1]  R. A. Chivers.  In vitro tissue welding using albumin solder: bond strengths and bonding temperatures , 2000 .

[2]  M. D. Thouless,et al.  Use of a cohesive-zone model to analyze the fracture of a fiber-reinforced polymer-matrix composite , 2005 .

[3]  P. Davies,et al.  Mixed mode failure criteria for a glass/epoxy composite and an adhesively bonded composite/composite joint , 2000 .

[4]  Zhigang Suo,et al.  Experimental determination of interfacial toughness curves using Brazil-nut-sandwiches , 1990 .

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

[6]  C. Shih,et al.  Crack extension and kinking in laminates and bicrystals , 1992 .

[7]  N. Fleck,et al.  Analysis of a wavy crack in sandwich specimens , 1992 .

[8]  H. Chai.  The characterization of Mode I delamination failure in non-woven, multidirectional laminates , 1984 .

[9]  Jr. J. Crews,et al.  Mixed-Mode Bending Method for Delamination Testing , 1990 .

[10]  De Xie,et al.  Computation of Energy Release Rates for Kinking Cracks based on Virtual Crack Closure Technique , 2004 .

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

[12]  Jan K. Spelt,et al.  Mixed-mode fracture characterization of adhesive joints , 1994 .

[13]  J. G. Williams,et al.  On the analysis of mixed-mode failure , 1992, International Journal of Fracture.

[14]  John H. Crews,et al.  The mixed-mode bending method for delamination testing , 1989 .

[15]  David A. Dillard,et al.  Numerical analysis of directionally unstable crack propagation in adhesively bonded joints , 2001 .

[16]  G. Fernlund,et al.  Mixed Mode Energy Release Rates for Adhesively Bonded Beam Specimens , 1994 .

[17]  T K Obrien,et al.  Mixed-mode strain-energy-release rate effects on edge delamination of composites , 1984 .

[18]  M. D. Thouless,et al.  Use of mode-I cohesive-zone models to describe the fracture of an adhesively-bonded polymer-matrix composite , 2005 .

[19]  Anthony G. Evans,et al.  Kinking of a Crack out of an Interface: Role of In‐Plane Stress , 1991 .

[20]  H. Chai.  A note on crack trajectory in an elastic strip bounded by rigid substrates , 1986 .

[21]  H. Chai.  On the correlation between the mode I failure of adhesive joints and laminated composites , 1986 .

[22]  W. G. Knauss,et al.  II – On the Problem of Crack Extension in Brittle Solids Under General Loading , 1978 .

[23]  S. Mall,et al.  Criterion for mixed mode fracture in composite bonded joints , 1986 .

[24]  J. R. Reeder,et al.  Nonlinear Analysis and Redesign of the Mixed-Mode Bending Delamination Test , 1991 .

[25]  J. H. Crews,et al.  Redesign of the Mixed-Mode Bending Delamination Test to Reduce Nonlinear Effects , 1992 .

[26]  Norman A. Fleck,et al.  Brittle fracture of adhesive joints , 1992 .

[27]  J. K. Spelt,et al.  The effect of geometry on the fracture of adhesive joints , 1994 .

[28]  C. Atkinson,et al.  Combined mode fracture via the cracked Brazilian disk test , 1982, International Journal of Fracture.

[29]  J. Rice,et al.  Slightly curved or kinked cracks , 1980 .

[30]  Robert O. Ritchie,et al.  Finite crack kinking and T-stresses in functionally graded materials , 2001 .

[31]  John W. Hutchinson,et al.  Crack deflection at an interface between dissimilar elastic-materials , 1989 .

[32]  Norman A. Fleck,et al.  Crack path selection in a brittle adhesive layer , 1991 .

[33]  D. Wilkins.  Effects of Defects in Composite Materials , 1984 .