2008 JAN 21 - (VerticalNews.com) -- "A nanoparticle dispersion is known to enhance the mechanical properties of a variety of polymers and resins. In this work, the effects of silica (SiO2) nanoparticle loading (0-2 wt%) and ammonia/ethylene plasma-treated fibers on the interfacial and mechanical properties of carbon fiber-epoxy composites were characterized," scientists in the United States report.

  "Single fiber composite (SFC) tests were performed to determine the fiber/resin interfacial shear strength (IFSS). Tensile tests on pure epoxy resin specimens were also performed to quantify mechanical property changes with silica content. The results indicated that up to 2% SiO2 nanoparticle loading had only a little effect on the mechanical properties. For untreated fibers, the IFSS was comparable for all epoxy resins. With ethylene/ammonia plasma treated fibers, specimens exhibited a substantial increase in IFSS by 2 to 3 times, independent of SiO2 loading. The highest IFSS value obtained was 146 MPa for plasma-treated fibers. Interaction between the fiber sizing and plasma treatment may be a critical factor in this IFSS increase. The results suggest that the fiber/epoxy interface is not affected by the incorporation of up to 2% SiO2 nanoparticles," wrote C. Lew and colleagues, Cornell University ...read more

  2008 JAN 21 - (VerticalNews.com) -- "The effectiveness of polyethyleneimine (PEi) dendrimer as a novel graded-modulus interphase material in polymeric composites is discussed in the context of core (polystyrene)-shell (PEi) nanoparticles affecting the mechanical properties of epoxy. The dendrimer is grafted onto the surface of polystyrene (PS) particles via a free radical polymerization reaction of styrene monomers in a non-aqueous polar solvent with t-butyl hydroperoxide (TBHP) as initiator and mild heating," researchers in the United States report ...read more

  2008 JAN 21 - (VerticalNews.com) -- "Several creatures including insects, spiders and lizards have developed a unique clinging ability that utilizes dry adhesion. Geckos, in particular, have developed the most complex adhesive structures capable of smart adhesion - the ability to cling to different smooth and rough surfaces as well as detach at will," scientists in the United States report.

  "These animals make use of about three million microscale hairs (setae) (about 14000/mm(2)) that branch off into hundreds of nanoscale spatulae (about a billion spatulae). Van der Waals forces are the primary mechanism utilized to adhere to surfaces, and capillary forces are a secondary effect that can further increase adhesion force. The hierarchical surface construction gives the gecko the adaptability to create a large real area of contact with surfaces. Modeling of the gecko attachment system as a hierarchical spring model has provided insight into adhesion enhancement generated by this system. It is shown that a multi-level hierarchical structure produces adhesion enhancement, and this enhancement increases with an increase in applied load and a decrease in the stiffness of springs. A significant adhesion enhancement occurs when the maximum spring deformation is greater than two to three times the root mean square amplitude of surface roughness. Although a gecko is capable of producing on the order of 20 N of adhesion force, it retains the ability to remove its feet from an attachment surface at will. Adhesion design databases for biomimetic attachment systems are presented. These adhesion design databases are useful for understanding biological systems and for guiding the fabrication of biomimetic attachment systems. A man-made fibrillar structure capable of replicating gecko adhesion has the potential for use in dry, superadhesive tapes that would be of use in a wide range of applications," wrote B. Bhushan and colleagues, Ohio State University ...read more