Quasi-static indentation response of balsa wood sandwich composites for shipbuilding: Effect of replacing glass fibers with basalt fibers

This study investigates the quasi-static indentation response of end-grain balsa wood sandwich composites with glass, basalt, glass-carbon, and basalt-carbon FRP facesheets. The effects of facesheet configuration, indenter diameter, and loading rate were evaluated using 17 and 20 mm spherical indenters at 1.25 and 2.5 mm/min. ANOVA results showed that facesheet configuration and indenter diameter significantly affected the response, while loading rate showed no significant main effect, although significant interactions were found for the maximum contact load. Replacing glass with basalt generally increased the maximum contact load and displacement at maximum load, while the absorbed energy up to the maximum contact load increased by up to 48.26% in the non-carbon configuration. Carbon hybridization increased the maximum contact load by up to 33.13% and the absorbed energy by up to 78.47%, while reducing the initial indentation rigidity. The main failure modes were matrix cracking, fiber breakage, facesheet delamination, balsa core crushing, and core/facesheet debonding. The results show that basalt fibers are a promising alternative to glass fibers for improving load-bearing capacity and energy absorption under localized indentation, while carbon hybridization further improves maximum load and deformation capacity.