Mode I DCB testing of composite laminates reinforced with z-direction pins: a simple model for the investigation of data reduction strategies

The applicability of standard composite mode I interlaminar toughness data reduction schemes is investigated for composites reinforced by inserting straight pins in the z-direction. A simple model of a z-pinned mode I test is used to generate load, displacement and crack length data. Data reduction schemes are applied to the model data and the resulting toughness is compared to the true toughness. These schemes are shown to be inaccurate for the initial stage of crack growth, during which the zone bridged by z-pins is developing and an improved scheme is proposed. Beyond this stage, the toughness is most accurately predicted if the ‘developing’ data is omitted.