No abstract

Carbon-based nanomaterials are promising reinforcing elements for the development of “smart” self-sensing cementitious composites due to their exceptional mechanical and electrical properties. Significant research efforts have been committed on the synthesis of cement-based composite materials reinforced with carbonaceous nanostructures, covering every aspect of the production process (type of nanomaterial, mixing process, electrode type, measurement methods etc.). In this study, the aim is to develop a well-defined repeatable procedure for the fabrication as well as the evaluation of pressure-sensitive properties of intrinsically self-sensing cementitious composites incorporating carbon- based nanomaterials. Highly functionalized multi-walled carbon nanotubes with increased dispersibility in polar media were used in the development of advanced reinforced mortar specimens which increased their mechanical properties and provided repeatable pressure-sensitive properties.

No abstract

A polyamide (PA) 12-based thermoplastic composite was modified with carbon nanotubes (CNTs), CNTs grafted onto chopped carbon fibers (CFs), and graphene nanoplatelets (GNPs) with CNTs to improve its thermal conductivity for application as a heat sink in electronic components. The carbon-based nanofillers were examined by SEM and Raman. The laser flash method was used to measure the thermal diffusivity in order to calculate the thermal conductivity. Electrical conductivity measurements were made using a Keithley 6517B electrometer in the 2-point mode. The composite structure was examined by SEM and micro-CT. PA12 with 15 wt% of GNPs and 1 wt% CNTs demonstrated the highest thermal conductivity, and its processability was investigated, utilizing sequential interdependence tests to evaluate the composite material behavior during fused filament fabrication (FFF) 3D printing processing. Through this assessment, selected printing parameters were investigated to determine the optimum parametric combination and processability window for the composite material, revealing that the selected composition meets the necessary criteria to be processable with FFF.

Curved bladelets on wind turbine blades play an important role in improving the performance and efficiency of wind turbines. Implementing such features on the tip of wind turbine blades can improve their overall aerodynamic characteristics by reducing turbulence and loading without hindering lift generation and overall efficiency, thus leading to increased energy capture and reduced costs over the life of the turbine. Subjecting the integrated blade tip to optimization procedures can maximize its beneficial contribution to the assembly in general. Within this context, a systemic workflow is proposed for the optimization of a curved bladelet implemented on a wind turbine blade. The approach receives input in the form of an initial tip geometry and performs improvements in two distinct stages. Firstly, shape optimization is performed directly on the outer shape to enhance its aerodynamic properties. Subsequently, the topology of its interior structure is refined to decrease its mass while retaining its improved airflow characteristics. The proposed workflow aims to approach blade tip optimization holistically, both in terms of aerodynamic performance and structural capabilities; is computationally validated via fluid dynamics studies and finite element analysis to evaluate the performance augmentation achieved through it; and is further coupled with additive manufacturing for the production of prototype parts, benefiting from the manufacturing flexibility offered by digital fabrication technologies. The optimized bladelet model presented an approximate 30% improvement in the torque generated on it, while maintaining only 70% of its original mass, effectively contributing to a 0.81% increase to the total torque generated by the blade, consequently confirming the effectiveness of the proposed methodology.

No abstract

their solubilization characteristics towards specific drugs. [4,5] The major advantage of AmBCs is that they can be prepared from a huge variety of different monomers in order to achieve the desired properties of the final AmBC chain according to the demands of specific applications. [10] An increasing number of copolymers possessing a stimuli-responsive block, responding to the alteration of its environment, [11,12] such as temperature, [6,9,13] pH, [3,14] or ionic strength, [4][5][6][7]14] has appeared in the literature, [3,4,15] The response (which in most cases leads to selfassembly) takes place when an AmBCs is dissolved in an aqueous medium. The phenomenon can be reversible, upon the variation of its environmental conditions (e.g., pH and temperature), [13] Thermoresponsive polymers show a distinct change in properties upon a large or small change in solution temperature. With regards to the thermoresponsive transition, depending on the system under investigation, there is a critical temperature at which segregation is due to the solvophobic block self-assembly, and in particular formation/disassembly of polymer aggregates in solution, [13,16] Thermoresponsive polymers are used for biomedical applications including drug delivery, [17] tissue engineering and gene delivery, [18,19] Materials with custom-designed responsive elements have the ability to significantly enhance the delivery of therapeutics agents. [17] In the center of interest of the present study is the development of new thermoresponsive AmBCs. The RAFT polymerization process has quickly become a powerful and versatile technique for the synthesis of a wide range of organic diblock copolymers and nano-objects of controllable size, morphology and surface functionality. This approach offers many potential applications, such as efficient microencapsulation vehicles and sterilizable thermoresponsive hydrogels for the cost-effective long-term storage of mammalian cells. [1] More recently, block copolymer self-assembly in solution to form spherical micelles, worm-like micelles and vesicles has been studied with potential applications in the field of drug, protein/peptide, and nucleic acid delivery. [1][2][3][4]13] In practice, relatively few vinyl monomers that may lead to thermoresponsive polymers have been tested for RAFT polymerization, such as N-isopropyl acrylamide (NIPAM), [7,14,[20][21][22][23][24] oligo(ethylene glycol) methacrylates, [25,26] vinyl-caprolactam, [27] and 2-hydroxypropyl methacrylate (HPMA). [1,21,25,28,29] In each case the corresponding Polymer Chemistry Thermoresponsive amphiphilic poly(hydroxyl propyl methacrylate)-b-poly(oligo ethylene glycol methacrylate) block copolymers (PHPMA-b-POEGMA) are synthesized by RAFT polymerization, with different compositions and molecular weights. The copolymers are molecularly characterized by sizeexclusion chromophotography, and 1 H NMR spectroscopy. Dynamic light scattering (DLS) and static light scattering (SLS) experiments in aqueous solutions show that the copolymers respond to temperatu...

In this work, materials that as additives in cement promote self-sealing/healing properties by the gradual release of water they absorb were synthesized, characterized and evaluated. Specifically, hybrid SAPs that absorb high ammounts of water encapsulated with SiO2 that facilitates their incorporation in the matrix since it improves their chemical affinity were investigated. The structure and morphology of the fabricated SAPs were characterized analytically and confirmed the synthesis of P(MAA-co-EGDMA)@SiO2 nanocomposite. Its particle size is expected to reduce the size of the pores formed due to the absorbing/desorbing water process during the mixing and curing of cement. Moreover, the water absorbance of the above mentioned material as well as its ability to maintain its original structure during subsequent cycles of absorbing/desorbing water from different mediums and specifically from distilled water (DW) and cement slurry filtrate (CS) were evaluated. CS was chosen to mimic the cementitious environment considering the presence of various ions and its pH value (~ 12). The results revealed that the absorption ratio of P(MAA-co-EGDMA)@SiO2 in DW and CS was higher than 1500 wt.% its original dry weight, while SEM pictures proved that the hybrid SAPs maintained their structure after the water absorption tests.