Natural Frequency and Damping Properties of Composite Sandwich Materials Manufactured using Vacuum-Assisted Resin Infusion, Vacuum Bagging, and Hand Lay-Up

Vibration testing was conducted on composite sandwich structures manufactured using different fabrication techniques, including vacuum-assisted resin infusion, vacuum bagging, and hand lay-up. Two carbon fiber orientations—twill and unidirectional—were evaluated, with each classification further analyzed in three-layer configurations: 2C2, 3C3, and 4C2. Vinyl ester resin was employed as the matrix, while Divinycell foam served as the core material. Experimental results indicated that structures with unidirectional fibers exhibited higher fundamental frequencies compared to those with twill fibers. Among the manufacturing techniques, vacuum-assisted resin infusion produced composites with the highest natural frequency across all sample variations. The damping ratio values showed significant variability, with the 3C3 configuration demonstrating a reduced damping ratio compared to other sample variations across fiber types and manufacturing methods. Further research is required to investigate discrepancies in sample behavior, fabrication methodologies, and evaluation techniques.