Interlaminar Fracture Tests IFT

Historically, most attention has been devoted to mode I delamination growth to assess defects critically, as the first-generation composite systems exhibited low mode I fracture toughness when subjected to interlaminar normal stresses. The 

A number of methods have been applied to evaluate the experimental data recorded during the tests, and they may be classified into two types compliance method and direct fracture energy method. 

The compliance methods are all based on the equation for the critical strain energy release rate, Gic, based on Gurney and Hunt (1967) 

A classic expression for the compliance, C, can be obtained by taking into account the strain energy due to the bending moment for a perfectly elastic and isotropic material 

20) and (3.21) are called the load method and displacement method (Hashemi et al., 1989), respectively, since only load and displacement records corresponding to crack lengths are required to evaluate the Gic values, once the flexural modulus E of the beam is known. These equations also apply to the WTDCB specimens where the ratio of the crack length to width, a/b, is constant. 

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