- 22nd October 2018
- Posted by: Yanki Keles
– Novel micro and submicron nanoparticles were synthesised, and corresponding epoxy nanocomposite manufactured.
– Effects on cure and chemorheology of nanoparticles content percentage for the investigated nanocomposites were investigated.
– Effect of nanoparticles on fracture behaviour and glass transition temperature was investigated on all different NP filled nanocomposite also considering hybrid system at different weight percentage.
– Variation of nanocomposite bending modulus over the filler content with temperature was assessed.
– Effect of filler typology and percentage on high strain rate performance in compression, tensile and (still in progress) end notched bending has been studied.
Different fillers typologies have been tested, and for each of them different concentrations have been employed, in order to obtain the best results in term of fracture toughness and thermo-mechanical properties.
Figure: Investigated Piezo-elements for embedded sensor-actuator networks in CFRP Aerospace structures
The 5 filler typologies used are the following:
- Glassy Hyperbranched Polymers (HBPG): according literature the most suitable fillers used to enhance the fracture and impact resistance of a resin are the hyperbranched particles; however, HBPs may induce unwanted drawbacks over the final composite matrix, such as reduction of elastic modulus and glass transition temperature; the use of an HBPs characterized by an high Tg (higher than room temperature) can limit the matrix Tg breakdown increasing simultaneously the nanocomposite fracture toughness;
- Rubbery Hyperbranched Polymers (HBPR): liquid rubbers were the first class of fillers employed to increase the impact resistance of composites and adhesives; this materials lead to different drawbacks, such as the reduction of hosting matrix thermomechanical properties and the strong increase of the uncured mixture viscosity, limiting their use in infusion process; the unique molecular architecture of hyperbranched polymers, which allows to obtain very high molecular weights without remarkable increase of the particles sizes, is extremely appreciated for the production of fillers that do not affect the rheological properties of the hosting matrix; therefore, using rubbery HBPs it is possible to increase the fracture toughness of the matrix without remarkable increase in the resin viscosity;
- Silica Nanoparticles (NPs): between the inorganic fillers, silica nanoparticles has been widely employed for the enhancing of epoxy resins thermomechanical properties; the use of these particles can increase the fracture toughness of the epoxy matrix without loss in glass transition temperature, which is one of the main HBPs drawbacks;
- Carbon Nanofibers (GANF): the aspect ratio of a filler is a critical parameter influencing its toughening efficiency; in particular, nanofibers can efficiently limit the crack opening and propagation through a bridging mechanism, and for this reason GANFs can be excellent candidates as epoxy resin fracture tougheners;
- Core/Shell Nanoparticles (CS): properly designed core-shell particles can be employed in order to synergically exploit the different phases comprising the particle. Specifically, hard inorganic core increases the glass transition temperature of the hosting matrix, while the hyperbranched shell induces energy dissipation through local deformation enhancing the performance in term of fracture and impact resistance.
All these nanocomposites sets have been tested using different methods: Differential Scanning Calorimetry (DSC), Dynamic Mechanic Analysis (DMA), Scanning Electron Micrograph (SEM), Fracture Toughness tests.
Considering the fracture toughness enhancement, as well as the thermomechanical and rheological results, the chosen nanocomposites for the manufacturing of epoxy modified reinforced composites plates is RTM6 + 5wt%HBPG. Manufacturing of neat resin reinforced composites plates is actually in progress.
Development of Tailored Embeddable Sensor-Actuator Layers (TEmSAL)
Figure: Exemplary screen printing mask and printed conducting paths for TEmSAL
Developing different approaches for pre-manufactured sensor/ actuator layer for CFRP parts and structures: Tailored Embedded Sensor and Actuator Layers – TEmSAL
- Can be pre-manufactured for „off-the-shelf“ usage
- Cost effective
- Easy to design
- Highly automated (manufacturing, positioning, integration)
- Tailored sensing capabilities for customized applications and parts (number of sensor and positioning)
- Low impact on mechanical properties of the CFRP structure: in-depth characterisation of different carrier layer materials
- Focus: optimization of delamination behaviour (bonding capabilities and crack propagation properties