Process parameters optimization of double-vacuum-bag technology for carbon fiber/resin composites

Double-vacuum-bag (DVB) process, as an effective out-of-autoclave (OoA) technology, can manufacture composite materials with low void content and high mechanical properties. Therefore, this paper aimed to achieve low void content, the effects of pressure difference between inner and outer bags, dwelling temperature, and dwelling time on the void of composite laminates were studied based on orthogonal experimental method. The void content and morphology of laminates were statistically analyzed, by observing the microscopic images of the samples on cross-section. The results show that the pressure difference between the inner and outer bags has a significant impact on the void content and morphology, while the dwelling temperature and dwelling time have little effect. In addition, with the variance analysis and extreme difference analysis, the optimal process parameters were determined as follows: pressure difference between inner and outer bags was 0 MPa, dwelling temperature was 110°C, and dwelling time was 15 min. The void content of composite laminates manufactured under these parameters is 0.07%, less than 1% requirement for aerospace components, and interlaminar shear strength (ILSS) is 110 MPa, which is 54.93% higher than the single-vacuum-bag (SVB) process. Generally, the void content and ILSS reached the level of hot press process with 0.6 MPa. Highlights: Influence of different DVB process parameters on void were studied. Void content manufactured with the optimal DVB process parameters was less than 1%. ILSS of laminate with the optimal DVB process parameters was equal as hot press process.