Abstract: The effects of different stitch densities and different stitch thread thickness on the in-plane mechanical properties of carbon fiber eight-five-face satin-stitched composite materials were studied. The in-plane fiber waviness due to stitch thread implantation was measured by microscope observation, and the correlation between mechanical properties and in-plane fibers waviness was analyzed. The results show that the stitch has certain influence on the in-plane properties. As the stitch density becomes larger and the stitch thread becomes thicker, the in-plane mechanical properties show a decreasing trend and the decreasing range increases. Microscopic analysis shows that in-plane fiber waviness is characterized by the waviness amplitude and waviness angle in-plane, and the main factors that affect the mechanical properties of stitched laminates is in-plane fiber. Under the same stitch thread thickness, as the stitch density becomes dense, the waviness amplitude of the in-plane fiber is almost unchanged, and the waviness angle of the in-plane fiber increases first and then decreases, and the in-plane mechanical properties decrease as a whole. At the same stitch density, the waviness amplitude and angle of the in-plane fiber increased with the stitch thread thickness, and the decreasing trend of the strength had a strong correlation with the waviness amplitude and angle of the in-plane fiber, where the quadratic function correlation coefficient ranged from 0.89 to 0.97.

Key words: eight five-fly face satin, stitched composite materials, in-plane mechanical properties, the in-plane fiber waviness