Double cantilever test configuration

Considerable plastic deformation can occur if the thin film is made of a ductile metal, and there is no way to separate the actual work of interface separation from the work dissipated in plastic deformation. In any case, if the delamination advances with a more or less steady local stress field, the change in energy that defines the energy release rate is taken to be that given in Section 4.2.1 as 

measurement of as a function of length a during delamination growth provides an estimate of T. As described by Oh et al. (1988) and Evans et al. (1999), the double cantilever specimen has been used to evaluate the fracture energy of interfaces between thin films of such materials as Al and Cu and substrates such as AI2O3 and glass. 

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Fig. 2. Illustrations of forces to which adhesive bonds are subjected, (a) A standard lap shear specimen where the black area shows the adhesive. The adherends are usually 25 mm wide and the lap area is 312.5 mm. The arrows show the direction of the normal apphcation of load, (b) A peel test where the loading configuration, shown by the arrows, is for a 180° peel test, (c) A double cantilever beam test specimen used in the evaluation of the resistance to crack propagation of an adhesive. The normal application of load is shown by the arrows. This load is appHed by a tensile testing machine or other...

Standard Mode I Double Cantilever Beam specimens for delamination testing of a unidirectional (UD) IM7/977-2 composite were Z-pinned with two separate blocks of Z-Fiber reinforcement. The reinforced beam configuration was such as to provoke an unstable delamination, propagating between the two Z-pin blocks. Crack resistance curves for these specific geometry specimens of IM7/977-2 indicate that the unstable delamination cracks are arrested by the second Z-pin block, with the crack propagation resistance being dictated primarily by the Z-pinning density within a block. Acoustic emission analysis is used to interpret visual observations and other test data. 

Several testing techniques are possible which use different specimen configurations, different loading modes, and various loading frequencies. Marceau et al. have described results for thick adherend lap shear and double cantilever beam (DCB) specimens exposed to 140 F/100%... 

FIG. 20—Dimensions and configurations for double-cantilever beam test specimen. Specimen contoured to 3 llf + Mh + C, where C is a constant [28]. Ali vslues given in inches. (Note 1 in. = 25.4 mm.)... 

Initial damage (crack) was introduced by using a Double Cantilever Beam (DCB) configuration. Aluminum fixtures were used to avoid delamination of the composites during the DCB test. Grooves on both sides of the DCB specimen assured symmetric... 

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