High Strength and Impact Damage Tolerant Syntactic Foam for High Performance Sandwich Structures

摘要

This study explored a novel higher strength and higher impact tolerant syntactic foam for composite sandwich structures. A unique microstructure was designed and realized through a unique manufacturing technology. The foam was fabricated by dispersing rubber latex coated microballoons into a nanoclay and milled microfiber reinforced epoxy matrix. Each component was designed to contribute to a desired property of the foam. The nanoparticle and microfiber served to increase the strength and stiffness (stronger and stiffener); the microballoon served as a light-weight filler (lighter); and the rubber coating served to increase the toughness and the impact tolerance (tougher). The manufacturing process for developing this unique microstructure was developed. Both low velocity impact test and four- point bending test were conducted on the foam core and sandwich beams. The test results showed a considerable increase in energy absorption capacity and the capacity for retaining the residual bending strength. This multi-phase material contained structures bridging over several length-scales. The SEM pictures showed that several mechanisms were activated to collaboratively absorb impact energy, including microballoon crushing, interfacial debonding, matrix cracking, rubber pinning, fiber pull-out, and fiber bridge-over. The localized and microscale damage insured that the sandwich beams retained its strength after the impact.