Effects of Z-pin on moisture absorption property and damage mode under flexural load for carbon fiber composite

The effect of carbon fiber Z-pin on carbon fiber composite under moisture condition with and without flexural load was investigated in this work. Moisture absorption property and crack propagation of carbon fiber reinforced epoxy matrix composite and Z-pinned composite were evaluated under moisture only and moisture-coupled load conditions. The moisture property was evaluated by moisture content and microscopic morphology obtained using X-ray micro-computed tomography (X-ray mu CT). The microstructures inside composites and Z-pinned composites after moisture conditions and three-point flexural test were detected using X-ray mu CT and optical microscope. It illustrates that the moisture content of Z-pinned composites is higher due to the rich-resin pocket brought by the implantation of Z-pin. The cracks are obvious inside Z-pinned composites after moisture-coupled load conditions. It is attributed to the implantation of each pin which is the weak point for stress concentration and crack formation. Failure morphologies on the surface of composites and Z-pinned composites are different under different moisture conditions. Less macro-interlayer cracks are detected on the surface of Z-pinned composites, and plenty of microcracks initiating from pins are observed.