Shear properties of a carbon/carbon composite with non-woven felt and continuous fibre reinforcement layers

This study examines the shear properties of a 2D PAN-CVI carbon/carbon composite whose reinforcement layers are formed from a non-woven duplex cloth comprising a continuous fibre layer needled to a short fibre felt layer. Composites of three lay-ups were tested in several orientations using the Iosipescu (V-notched beam) shear test. Material anisotropy means that shear failure stresses and shear moduli are required in several orientations for structural analysis. It was necessary to mitigate the effect of specimen twisting by using strain gages on both sides of the specimens. The approximate ranges of measured shear failure stresses were 30–45 MPa in-plane and 8–22 MPa interlaminar. Shear moduli ranged between 6–16 GPa in-plane and 1–3 GPa interlaminar. While the presence of flaws in these composites leads to scatter in properties, the effect of bulk density on interlaminar properties was clearly observed.