Analysis of multiple impact damage of three-dimensional four-directional braided composite materials under different punch heads

Impact tests are carried out with cylindrical，conical and spherical punches respectively，and the response characteristics of specimens under different punch impact are discussed. The internal damage of the specimen is detected by ultrasonic C-scan instrument，and the law and process of damage expansion under impact are analyzed. The experimental results show that the shape of the punch is an important factor affecting the damage mode of the specimen. In the impact test，the spherical punch cause the most serious damage to the material，comparing to the columnar punch cause less damage，but the damage range is larger. The impact response of the conical punch to the specimen is similar to that of the spherical punch，and the damage area of the two punch to the specimen is not much different，but the damage of the conical punch to the specimen is light. The weaving angle of the material also obviously affects the impact resistance of the material. The impact resistance of the material increases with the increase of the weaving angle. In terms of damage expansion on the specimen，materials with small weaving angles tend to be damaged along the longitudinal direction. The damage of large woven angle materials tends to spread to all sides. In the impact test，the damage process of the specimen includes the longitudinal tensile failure of the fiber bundle，the transverse tensile failure of the fiber and the matrix，and the transverse compression failure.