Hybrid HA/Ge hydrogel particles are embedded in a secondary HA network to improve their structural integrity. The internal microstructure of the particles is imaged through TEM. CSLM is used to identify the location of the Ge molecules in the microgels. Through indentation tests, the Young’s modulus of the individual particles is found to be 22 ± 2.5 kPa. The overall shear modulus of the composite is 75 ± 15 Pa at 1 Hz. The mechanical properties of the substrate are found to be viable for cell adhesion. The particles’ diameter at pH = 8 is twice that at pH = 5. The pH sensitivity is found to be appropriate for smart drug delivery. Based on their mechanical and structural properties, HA–Ge hierarchical materials may be well suited for use as injectable biomaterials for tissue reconstruction.
Matrix enhancement using nanotubes is one method to produce hybrid, multiscale fiber reinforced polymer (FRP) composites with improved interlaminar performance and added functional properties. Carbon nanotubes (CNTs) have been shown to be promising, and recent advances in the manufacturing of boron nitride nanotubes (BNNTs), which are largely unexplored for structural reinforcement of hybrid composites with microscale fibers, offer new opportunities to employ BNNTs in reinforced hybrid composite structures. This study investigates the shear and impact properties of BNNT hybrid composites, specifically glass fiber−epoxy/BNNT composite laminates. Two manufacturing techniques were used to fabricate the specimens: wet layup and vacuum-assisted resin transfer molding (VARTM). Shear punch, short beam shear, and modified Charpy tests were selected for their relevance to complex loading systems that involve shear, such as ballistic or other impact loading. The addition of 1 wt % BNNTs to the epoxy resin was found to improve the performance of the laminates: 8% increase in specific shear punch strength, 15% increase in the specific short beam shear strength, and an average of 22% increase in the specific fracture energy per area in modified Charpy tests. Improvements were lower in test cases approaching pure shear, which led to the conclusion that BNNT reinforcement most effectively improves laminate performance in more complex loading situations in which an element of normal stress, such as bending, is present. As such, BNNT reinforcement, which offers different functional properties than CNTs, is also promising to improve the impact performance in multiscale hybrid composites.
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