Fabrication of Mechanically Strong Honeycombs with Aerogel Cores

Honeycomb aerogel composites were fabricated by reinforcing selected regions of a native aerogel matrix using photopolymerization. First, alcogels were synthesized by hydrolysis–condensation of a siloxane, and by adding a multifunctional acrylic monomer and a visible-light initiator to the gelation solution. Alcogels were then placed on a programmable translation stage and exposed to a laser. Polymerization and mechanical reinforcement were induced in the exposed regions. After exposure alcogels were dried supercritically. Thermal conductivity and out-of-plane modulus of the resulting honeycombs could be varied between values typical of native aerogels (11 mW/mK and 0.75 MPa) and those of uniformly polymerized composites (65.8 mW/mK and 36.26 MPa) by varying the translation stage speed between 2 and 3 mm/s. The results were interpreted using a rule-of-mixtures model. The mechanical properties of the composites were also investigated using finite element analysis.