Characteristics and homogenization removal methods of ultraviolet femtosecond laser processing of aerospace AFRP

An experimental investigation of typical projectiles penetrating multi-layer spaced Q355B steel targets was conducted to study the trajectory characteristics of elliptical cross-section projectiles penetrating multi-layer spaced steel targets. Numerical simulations were performed on LS-DYNA finite element software and typical results obtained were validated by experimental results. The attitude and trajectory parameters in the penetration process and the deflection mechanism of the projectile were obtained. The influence of cross-section shape, the minor-to-major axis length ratio of the projectile cross-section, initial velocity, rotation angle, and incident angle on the penetration trajectories and attitude deflection was investigated. The research results show that the penetration trajectory stability of the circular cross-section projectile is better than the elliptical and asymmetric elliptical cross-section projectiles when the rotation angle is 0°. As the minor-to-major axis length ratio increases, the trajectory is more stable. The trajectory deflection reduces with a higher initial velocity. When the rotation angle is 90°, the penetration trajectory of both symmetric and asymmetric elliptical cross-section projectiles in the incident plane is the most stable, and the trajectory deflection of the two projectiles in the horizontal plane reaches its maximum at rotation angles of 45° and 90°, respectively. The trajectory stability of an asymmetric elliptical projectile, when the rotation angle is obtuse, is better than that at the acute angle. When the incident angle is in the range of [0°, 50°], the trajectory instability and attitude deflection of the projectile increase with the increase of incident angle and then decrease, and both reach the largest when the incident angle is about 30°. It is also found that the projectile will separate from the target during the penetration stage of the projectile nose when penetrating a thin steel target in a stable attitude. When the projectile penetrates a thin steel target at a large attack angle, the attachment of the projectile and target mainly occurs on the upper surface of the projectile.