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Within this study the influence of adding 5 vol % of silica nanoparticles, obtained via a sol-gel process, on an Araldite-F epoxy was investigated. To characterize toughening effects, compact tension specimens were used to obtain K IC and G IC . Additionally, tensile strength and EModulus were measured as well as differential scanning calorimetry and dynamic mechanical thermal analysis were carried out to evaluate the influence on the thermal properties of the epoxy because of addition of the particles. Electronic microscopy was used to check dispersion quality and fracture surfaces, in transmission mode and scanning mode, respectively. The addition of 5 vol %. silica-nanoparticles could improve the stiffness and the toughness of an epoxy resin at the same time.

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This study reveals the influence of silica nanoparticles on the cure reactions of a diglycidyl ether of bisphenol A epoxy resin. As soon as the silica nanoparticles are added to the neat resin (1, 3, and 5 vol.‐%), the total degree of conversion increases with an increasing amount of nanoparticles, and the cure reaction shows a more complex autocatalytic behaviour, which can not be described by a traditional kinetic model. Results from subsequent thermo‐mechanical analyses confirm an alteration in the microstructure attributable only to the presence of the nanoparticles in the curing stage. An amino‐rich interphase around the reactive treated particles is formed, which shifts the resin/hardener ratio, and benefits the homopolymerization of the epoxy and leads to a more highly crosslinked epoxy network. At the same time, the nanophase consists of a core‐shell structure with the rigid particle inside and a rubber‐like shell because of the excess hardener in this region.TEM image of two neighboring silica nanoparticles in the epoxy matrix showing a 2–3 nm altered interphase region.magnified imageTEM image of two neighboring silica nanoparticles in the epoxy matrix showing a 2–3 nm altered interphase region.

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The aim of this study was to investigate the scope of the recently developed polymerization molding system for polyamide 12 (PA12), especially with respect to the formation of carbon fiber-reinforced PA12 composites. Initial screening of PA12 composite formation was performed by means of an internal mixer in order to identify the suitable type of surface-treated carbon fiber (CF). The content of residual lauryllactam (LL) monomer reflected the influence of the CF-treatment on the polymerization molding involving anionic in situ polymerization of LL. The cryogenic fracture surfaces were analysed by scanning electron microscopy (SEM) in order to evaluate the adhesion quality between the components. Finally, a bench-scale polymerization molding process was established successfully for the fabrication of multi-axial laminates. Macromechanical tests and dynamic mechanical thermo-analysis (DMTA) indicated that the performance of the new polymerization molding process is very similar to that of state-of-the-art PA12/CF composites.

Fracture toughness and other mechanical properties of epoxies modified with nano-slica particles were measured to elaborate effects of nano-additives on fracture behaviour of the modified epoxies. Interlaminar fracture behaviours of the nano-silica modified CF/EP composites were subsequently investigated by conducting Mode-I and Mode-II interlaminar fracture toughness tests as well as transverse tension tests. It was found that the fracture toughness of the nano-silica modified epoxies and the interlaminar fracture toughness of nano-silica modified CF/EP composites have been increased significantly (>50%), while the strength and modulus of the materials remain unchanged or slightly higher. In particular, the nano-silica modified epoxies showed only very little reduction in the glass transition temperature (Tg).