Quasi-static crack growth

Analysis of crack growth in viscoelastic media is mainly limited to linear isotropic, homogeneous materials. Schapery(34) proposed the use of parameters similar to the J integral for quasi-static crack growth in a class of nonlinear viscoelastic materials subject to finite strains. 

Hutchinson, J.W. 1974, On steady quasi static crack growth. Harvard University Report, Division of Apphed Sciences, DEAP S 8. 

Nuismer, R. J. (1974) On the governing equation for quasi-static crack growth in linearly viscoelastic materials. J. Appl. Mech. 41, 631-634... 

Under test conditions (23°C, quasi-static), polypropylene has a semi-brittle behaviour, to a crack extent of I mm, and is brittle at larger crack growth. 

Jic is the critical value of the near-tip quasi-static fracture parameter J, i.e. the crack initiation toughness. As for ductile materials a stable crack growth can occur at J values several times the value J c, the non-dimensional tearing modulus Tr was proposed for defining the crack growth toughness [26] ... 

Sic mm critical 5 value for unstable crack growth, quasi-static loading, geometry-independent... 

Dean, R.H. and Hutchinson, J.W., 1980, Quasi static steady crack growth in small scale yielding. In Fracture Mechanics, ASTM STP 700, 383 405. 

The choice of whether to use the CT or SENB test is influenced by several factors. First, the amount of material available CT specimens are larger than SENB specimens so if the quantity of adhesive is limited, this would favor the SENB test. Second, the type of crack propagation observed the tests are quasi-static and unstable crack initiation from the initial defect is intended in the test. If stable growth is obtained the CT specimen will usually permit a greater length of crack propagation to occur than the SENB test. O Figure 20.1a shows the CT and O Fig. 20.1b shows the SENB test specimens. For either, it is necessary to mold bulk adhesive samples with sufiScient dimensions to satisfy the validity criteria (see below) and to be sufficiently void free (see Chap. 19 for more details on how this can be achieved for common adhesive types). 

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