Mechanical Properties and Failure Mechanisms of Carbon Fiber/Resin Composites with Hot Press, Single-Vacuum-Bag, and Double-Vacuum-Bag Processes

In order to compare the mechanical properties of materials, acquire the crack propagation law and failure mode under different processes of carbon fiber/resin composites, the hot press process, double-vacuum-bag (DVB) process, and single-vacuum-bag (SVB) process were used to manufacture laminates in this paper, the void content and void morphology of the composite materials were observed by ultrasonic C-scan, optical microscope, and scanning electron microscope. Four different types of mechanical tests were carried out: tensile, compressive, bending, and short-beam shear tests, and the fracture morphology of the specimens was observed and analyzed. The failure mechanisms of the materials under different processes were explored based on the stress analysis. It is found that in the materials manufactured by SVB process, voids can induce stress concentration effect, reduce the stress area and interlayer bonding force, and cracks are more prone to initiate and propagate around voids. These are all factors contributing to the reduction of bearing capacity and accelerating the failure process in the material. The void contents of laminates manufactured by DVB process and hot press process are extremely low, it is difficult for cracks to propagate within the material, and the composites can maintain excellent mechanical properties.