Effects of Ultrasonic Waves during Resin Impregnation on the Mechanical Properties of Unidirectional Composite Materials

Effects of ultrasonic vibrations on mechanical properties of fiber reinforced plastics were investigated during molding resin impregnation process in vacuum assisted resin transfer molding. The vacuum bag including the preformed each non-crimp fabrics (carbon and glass fibers) was placed in a water bath of an ultrasonic wave generator during resin impregnation. The mechanical properties of the laminates were evaluated through the mechanical strength tests and scanning electron microscope (SEM) observation. The results revealed that ultrasonic waves improved transverse tensile, flexural, interlaminar shear, and compressive strengths of the carbon fiber (CF) laminates and interlaminar shear and compressive strengths of the glass fiber (GF) laminates. It was found from SEM observation that the fracture modes of the CF and GF laminates processed using ultrasonic waves were resin fracture. Accordingly, the adhesion of the fiber/resin interface was improved by oscillating ultrasonic vibration during resin impregnation, leading to an increase of the interface strength.