A Method to Extract Interface Stress Intensity Factors Using Interlayers

2005 ◽  
Author(s):  
Sridhar Santhanam
Keyword(s):  
Stress Intensity ◽  
Interface Crack ◽  
Stress Intensity Factors ◽  
Crack Problem ◽  
Interface Stress ◽  
Mode I ◽  
Universal Relation ◽  
Intensity Factors ◽  
Infinite Blocks

A method is presented here to extract stress intensity factors for interface cracks in plane bimaterial fracture problems. The method relies on considering a companion problem wherein a very thin elastic interlayer is artificially inserted between the two material regions of the original bimaterial problem. The crack in the companion problem is located in the middle of the interlayer with its tip located within the homogeneous interlayer material. When the thickness of the interlayer is small compared with the other length scales of the problem, a universal relation can be established between the actual interface stress intensity factors at the crack tip for the original problem and the mode I and II stress intensity factors associated with the companion problem. The universal relation is determined by formulating and solving a boundary value problem. This universal relation now allows the determination of the stress intensity factors for a generic plane interface crack problem as follows. For a given interface crack problem, the companion problem is formulated and solved using the finite element method. Mode I and II stress intensity factors are obtained using the modified virtual crack closure method. The universal relation is next used to obtain the corresponding interface stress intensity factors for the original interface crack problem. An example problem involving a finite interface crack between two semi-infinite blocks is considered for which analytical solutions exist. It is shown that the method described above provides very acceptable results.

scholarly journals Determination of mode I stress intensity factors of complex configurations using strain gages

2008 ◽  
Vol 3 (7) ◽  
pp. 1239-1255 ◽  
Author(s):  
Sanda Swamy ◽  
Manda Srikanth ◽  
Kondepudi Murthy ◽  
Puthuveettin Robi
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Mode I ◽  
Strain Gages ◽  
Intensity Factors

scholarly journals Crack Paralleling an Interface Between Dissimilar Materials

1987 ◽  
Vol 54 (4) ◽  
pp. 828-832 ◽  
Author(s):  
J. W. Hutchinson ◽  
M. E. Mear ◽  
J. R. Rice
Keyword(s):  
Stress Intensity ◽  
Interface Crack ◽  
Stress Intensity Factors ◽  
Dissimilar Materials ◽  
Complex Stress ◽  
External Loading ◽  
Universal Relation ◽  
Intensity Factors ◽  
Elastic Solids ◽  
Complex Stress Intensity Factor

A crack paralleling a bonded plane interface between two dissimilar isotropic elastic solids is considered. When the distance of the crack from the interface is small compared to the crack length itself and to other length scales characterizing the geometry, a simple universal relation exists between the Mode I and Mode II stress intensity factors and the complex stress intensity factor associated with the corresponding problem for the crack lying on the interface. In other words, if the influence of external loading and geometry on the interface crack is known, then this information can immediately be used to generate the stress intensity factors for the sub-interface crack. Conditions for cracks to propagate near and parallel to, but not along, an interface are derived.

Interface Debonding Model and its Application to the Mixed Mode Interface Fracture Toughness

2002 ◽  
Vol 11 (3) ◽  
pp. 263-286 ◽  
Author(s):  
Masaki Omiya ◽  
Kikuo Kishimoto ◽  
Wei Yang
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity ◽  
Phase Angle ◽  
Interface Crack ◽  
Stress Intensity Factors ◽  
Mixed Mode ◽  
Characteristic Length ◽  
Interface Stress ◽  
Interface Debonding ◽  
Intensity Factors

The aim of this paper is to investigate the mixed mode fracture toughness of an interface crack. The crack propagation is simulated by modifying a cohesive interface model proposed by Ma and Kishimoto (Ma, F. and Kishimoto, K. (1996). A Continuum Interface Debonding Model and Application to Matrix Cracking of Composites, JSME Int. J. Series A, 39:496–507). Based on the internal variable theory of thermodynamics, a continuum interface constitutive model relating interface traction with interface separation has been developed. By introducing an interface damage variable, an evolution equation was derived to characterize the degradation of interfacial rigidity with interface debonding. This constitutive relation is embedded at the crack tip of the interface and the propagation of the interface crack is simulated by the Finite Element Method. The results show that the fracture toughness and fracture boundary curves of dissimilar materials depend on the definition of the characteristic length included in the interface stress intensity factors. By changing the characteristic length properly and normalizing with the critical stress intensity factors, the intrinsic fracture boundary curve can be obtained. This curve can be considered as the fracture criterion based on the interface stress intensity factors. The relation between the fracture toughness and the phase angle is also influenced by the characteristic length. By changing the phase angle, the fracture toughness data is located on the same trend curve and the numerical results are well consistent with the analytical decohesion energy for all material pairs.

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