Impact response and post-impact compression behavior of two-dimensional triaxially braided carbon fiber composites

The two-dimensional triaxially braided composites are prepared by the resin transfer molding process. The mechanical response of two-dimensional triaxially braided composite under high and low velocity impact are investigated through the air gun system and drop hammer impact test system with different energies. The delamination damage under different impact energies are obtained by ultrasonic C-scan to analyze the damaged failure characteristics. The behaviors of compression after impact are studied in combination with digital image correlation. It is shown that the damaged area of the two-dimensional triaxially braided composite increases proportionally with the low velocity impact energy， but the energy absorption increases almost 2 times. Severe damage occurs and extends along the axial fiber under impact with an energy of 6.7 J/mm， leading to a significant reduction in its residual strength. The ballistic limit velocity of the two-dimensional triaxial braided composite is about 138.5 m/s. The projectile is embedded in the plate. When the impact velocity is greater than the ballistic limit velocity， a rectangular hole is formed on the impact surface， and a tearing fracture can be observed on the back surface. The damage area decreases with the increase of the incident velocity.