Abstract
Three different fiber surface treatments were made to study their influences on drop-weight impact fracture resistance and static in-plane fracture toughness of injection-molded short glass fiberreinforced nylon 6 plates. Scanning acoustic microscopy (SAM) was used to study the microscopic deformation and fracture processes in detail. The SAM observation revealed several fundamental and quantitative features such as: (1) three-dimensional shape of the crack front, (2) three-dimensional distribution of fibers,
(3) matrix plastic deformation and/or matrix microcracking, and (4) fiber/matrix debonding and pull-out. These microscopic deformation and fracture features revealed some of the toughning mechanisms, which were then correlated with the macroscopic static and impact fracture properties. The excellent ultrasonic contrast between fiber and matrix could be accomplished by a large difference in acoustic impedance. The plastic deformation of matrix was detected by enhanced attenuation of surface waves. Moreover, fiber/matrix debonding and/or matrix microcracking were clearly observed due to the waves reflected at debonded or cracked interfaces.
