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In this work the over-leg bending (OLB) specimen is developed for mixed-mode I/II delamination characterization in composites. The traditional single-leg bending (SLB) specimen is modified by introducing the load eccentrically between the two supports of a three-point bending setup. The modified configuration is analyzed by using linear beam theories. The theories of transverse shear, Winkler-Pasternak-type elastic foundation, Saint-Venant effect, and crack tip shear deformation are incorporated in the analysis. Also, experiments are carried out on glass/polyester unidirectional specimens. Comparison between the results of analysis and experiment shows very good agreement. The traditional SLB and the novel OLB coupons are compared, and their advantages and drawbacks are highlighted. The newly developed OLB setup is relatively easier to perform and crack propagation may be simply investigated under displacement control.

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In this work a novel beam analysis of the end-loaded split (ELS) and over-notched flexure (ONF) specimens are presented. New compliance and strain energy release rate equations are developed incorporating crack tip deformation and transverse shear analysis. The Saint Venant effect at the clamped end of the ELS specimen is also considered. Unidirectional glass-polyester specimens are manufactured and experimental (initiation and propagation) tests are performed to confirm the theoretical models. The experimental data is evaluated by means of four reduction techniques: the exact beam theory, virtual crack closure technique, compliance calibration method, and direct beam theory. It is shown that the results by the four methods agree quite closely; however, the compliance calibration method is not recommended for initiation data reduction in the case of the ONF specimen. The ELS specimens suffer from relatively large displacements. Thus, propagation tests are not possible to be performed. The ONF test seems to be a better tool to evaluate the mode-II toughness of composite materials with low flexural modulus.