Manufacturing and low-velocity impact characterization of hollow integrated core sandwich composites with hybrid face sheets

In the current study, 3-D hollow integrated core sandwich composite laminates with and without additional face sheets were fabricated using vacuum assisted resin infusion molding process in multiple steps. For additional facing, plain weave S2-glass and twill weave carbon fabrics were used on top and bottom sides of the panels in four different monolithic (S2-glass only, carbon only) and hybrid (glass + carbon, one with S2-glass layer outside and other with carbon layer outside) combinations. Square samples of 100 mm sides were subjected to low-velocity impact loading using an instrumented impact testing machine at 3 energy levels of 15, 30 and 45 J. Three samples were tested at each energy level. Impact parameters like peak load, time to peak load, deflection at peak load, and absorbed energy were evaluated and compared for different types of laminates. Failure modes were studied by sectioning the samples and observing under optical microscope. Results of the study indicate that the provision of additional face sheets considerably enhances the damage resistance. Of different facings, glass facing sustained maximum load followed by glass–carbon hybrid, carbon–glass hybrid, and carbon facings.