Characterization of Three-Point Bending Behavior of Isogrid-Stiffened Epoxy Composite Structures with Multiscale Reinforcements of E-glass Fibers and Silica Nanoparticles

Grid-stiffened composite (GSC) structures have been maturely developed in aerospace, aircraft, and defense industries due to their attractive properties. These structures undergo various loading conditions in service. In the present study, Iso-GSC structures reinforced with silica nanoparticles (SiO2) have been investigated in terms of their capability to improve the mechanical properties during three-point flexural loading. The epoxy/SiO2 nanocomposites with different silica loadings (0, 1, 3 and 5 wt.%), and E-glass fibers at a fixed volume fraction (both in ribs and skin parts) were employed as the matrix and fibrous reinforcement in the specimens, respectively. Ultrasonic and mechanical routes were used to disperse the nanoparticles within the epoxy resin. The results of flexural test with the skin side loading showed that the flexural stiffness, maximum load capacity, and energy absorption of the isogrid specimens enhanced through matrix modification by silica nanoparticles. It was also found that the maximum value of improvement in the flexural properties was related to the specimen with 3 wt.% silica. In this case, up to 16%, 14%, and 26% increase in the flexural stiffness, maximum load capacity, and energy absorption was observed, respectively. In conclusion, this study suggested that the addition of nanoparticles is a promising method to improve the flexural properties of GSC structures.