Rigid particles have been incorporated into laminated composites, especially to enhance their bending performance attributed to the stiffening of the matrix phase (i) and the increased interlaminar shear resistance (ii). In order to better evaluate the improvement mechanism provided by the particulate inclusions, this work investigates the incorporation of micro-sized silica on the top, bottom and both surfaces of glass fibre laminates, mitigating the interference of the interlocking effect. Three-point bending, and impact tests are performed to evaluate the hybrid glass fibre composites containing 5, 7.5 and 10 wt% of micro silica. In addition, the effect of the micro silica particles into epoxy polymers is verified under tensile, compressive and abrasion tests. A finite element model is developed to simulate the three-point bending test and to better assess the behaviour of the composite laminate. Although silica particles lead to increased compressive modulus of the epoxy polymers, their positive effect on glass fibre composites under flexural loads is more evident when placed on the bottom side of the laminates subjected to the maximum tensile stress. The incorporation of 7.5 wt% silica microparticles at the bottom surface of the laminates achieves higher flexural strength and lower impact resistance.

There are situations in which bioactive products of interest in biotechnology turn out to be hydrophobic. To reach high uniform levels of such products in water-based host fluids, such as those existing in many biological environments, one strategy consists on dividing the bioactive product into tiny micrometer (or sub-micrometer) pieces, since these are much more amenable of being uniformly dispersed and stabilized in the host fluid. On the other hand, if the bioactive product must act at specific locations, these micrometer pieces need to be hold in place, an objective that may be achieved by encapsulating them in mats of fibers. Here we demonstrate how these tasks may be accomplished by resorting to the generation and control of electrified coaxial jets of a hydrophilic liquid surrounding the hydrophobic liquid carrying the bioactive substance. When the process is carried out inside a dielectric liquid, double oil/water/oil and simple oil/water emulsions may be formed. On the other hand, when the process runs in air and a biopolymer is added to the hydrophilic liquid, then non woven mats of beaded nanofibers, encapsulating the bioactive product in the beads, are generated.

Electro-hydro-dynamic (EHD) compound jets, with diameters in the micro and nanometric size range, from conical menisci of two co-flowing liquids, is a consolidated platform for the production of nanofibers with inner structure, in a process so-called coaxial electrospinning or co-electrospinning. In contrast to other multi-step template based procedures, the EHD methodology is much more simple and general since, firstly, a solid template is needless and, secondly, the process is seldom affected by the chemistry of the liquids. This gentle process allows selecting the liquid precursors depending on the application sought for the nanofibers. Here, we review different products obtained by this EHD technique: (1) solid and hollow carbon nanofibers from different precursors (polyacrylonitrile, polyvinylpyrrolidone and lignin), (2) nanofibers of biocompatible polymers encapsulating liquids in the form of beads, (3) spinning nanofibers of alginate and (4) in-fiber encapsulation of active microgels.

Composites have been widely used in engineering applications due to high strength to weight ratios. A large amount of materials used in aeronautics is based on composite materials. This provides motivation to improve the mechanical properties of the existing composite materials. When a glass fibre laminate is subjected to bending stresses, maximum compressive and tensile stresses are generated at its sides of the surface beam. Rigid particles have been added into laminate composites specially to enhance their bending performance attributed to the matrix stiffness and interlaminar shear resistance increases. In order to better assess the enhancement mechanism provided by particle inclusions, this work investigates the incorporation of micro-sized silica on the top, bottom and both surfaces of glass fibre laminates, mitigating the interference of the interlocking effect. Three-point bending and impact test were performed to evaluate hybrid glass fibre composites containing 5, 7.5 and 10% by weight silica. Although the silica particles lead to increased compressive modulus of epoxy polymers, their positive effect on glass fibre composite under flexural loads was more evident on the bottom beam side subjected to maximum tensile stress. The incorporation of 7.5wt% silica microparticles on the bottom surface of the laminates achieved higher flexural behaviour and lower impact resistance.