96 research outputs found
Self-Healing Structures in Aerospace Applications
No full textThe present paper relates to autonomically‐healing composites which function actively and quickly at temperatures reaching as low as −50° C while maintaining the performance of the current structural composites. This is achieved thanks to the high temperatures possible for the formulation cure without deactivating self‐repair activity
Use of Hoveyda-Grubbs' second generation catalyst in self-healing epoxy mixtures
No full textThe development of smart composites capable of self-repair on aeronautical structures is still at the planning stage owing to complex issues to overcome. A very important issue to solve concerns the components’ stability of the proposed composites which are compromised at the cure temperatures necessary for good performance of the composite. In this work we analyzed the possibility to apply Hoveyda–Grubbs’ second generation catalyst (HG2) to develop self-healing systems. Our experimental results have shown critical issues in the use of epoxy precursors in conjunction with Hoveyda–Grubbs’ II metathesis catalyst. However, an appropriate curing cycle of the self-healing mixture permits to overcome the critical issues making possible high temperatures for the curing process without deactivating self-repair activity
Effect of carbon nanotube and functionalized liquid rubber on mechanical and electrical properties of epoxy adhesives for aircraft structures
No full textNew electrical conductive adhesives based on Multi Wall Carbon Nanotubes (MWCNTs) and functionalized liquid rubber have been designed and characterized. The elastomeric domains play a very relevant role in enhancing flexibility and mechanical performance of the adhesive formulation. Lap shear adhesion tests have shown enhancements in the stress up to 69% for the sample containing 25 phr of elastomeric phase in the matrix. The inclusion of MWCNTs in the toughened adhesive can be advantageously employed for further enhancing adhesive properties simultaneously imparting electrical conductivity, which results of 11 orders of magnitude higher than the unfilled formulation
Health structure monitoring for the design of an innovative UAS fixed wing through inverse finite element method (iFEM)
No full textThe structural health monitoring (SHM) plays an essential role in system health management applications for aeronautic and space transportation vehicles, manned and unmanned. The unmanned aircraft systems (UAS) are also extremely needed in various fields of interest, from military to civilian (search and rescue, environmental surveillance and monitoring, entertainment). This work presents an innovative UAS fixed-wing design and control through an inverse finite element method-based, which compute the full-field displacements reconstruction of a three-dimensional shell/plate deformations from experimentally measured surface strains. The full-field displacements are useful for the preliminary design and inspections of the UAS loads, caused by maneuvers or gusts. Goal of this paper was to validate the high accuracy predictions of deformations afforded due to the inverse finite element method (iFEM). Overall formulation was based on the minimization of a least-squares functional that uses and compares the strains extracted due to embedded sensors with the strains of linear, first order shear-deformation theory. The test article was a thin plate equipped with embedded sensors (strain gauge sensors) which permit to extract surface strains in real-time, used as input data for shape sensing. The plate was used to approximate an UAS wing box section, in further work analyzed
Rheological, Thermal and Mechanical Characterization of Toughened Self-Healing Supramolecular Resins, Based on Hydrogen Bonding
No full textThis paper proposes the design of toughened self-healing supramolecular resins able to fulfill functional and structural requirements for industrial applications. These new nanocomposites are based on compounds acting as promotors of reversible self-healing interactions. Electrically conductive carbon nanotubes, selected among those allowing to reach the electrical percolation threshold (EPT) with a very low amount of nanofiller, were dispersed in the self-healing polymeric matrix to contrast the electrical insulating properties of epoxy matrices, as required for many applications. The formulated supramolecular systems are thermally stable, up to 360 °C. Depending on the chemical formulation, the self-healing efficiency η, assessed by the fracture test, can reach almost the complete self-repairing efficiency (η = 99%). Studies on the complex viscosity of smart nanocomposites highlight that the effect of the nanofiller dominates over those due to the healing agents. The presence of healing compounds anchored to the hosting epoxy matrix determines a relevant increase in the glass transition temperature (T(g)), which results in values higher than 200 °C. Compared to the unfilled matrix, a rise from 189 °C to 223 °C is found for two of the proposed formulations
Dynamic mechanical properties of structural self-healing epoxy Resins
No full textIn this paper, we report the study and characterization of a multifunctional autonomically
healing composite containing solid particles of Grubbs’ first generation catalyst and poly(ureaformaldehyde)
microcapsules filled with liquid DCPD. This system, already reported in literature,
in some respects shows great potential for epoxy structural composites: however, other aspects have
to be explored in order to put to use in advanced applications. Here, we have determined the curing
process to obtain the best mechanical performance without deactivating the self-repair activity of
the material. It has been found that, for the same curing cycle, the presence of catalyst powder
causes a slight decrease in the elastic modulus value with respect to the epoxy matrix. A large
recovery in this performance is gained for the self-healing specimen, proving that the microcapsules
contribute to improve the mechanical characteristics of the self-healing sample
MULTIFUNCTIONAL SELF-HEALING COMPOSITE MATERIAL FOR AERONAUTICS APPLICATIONS
No full textThe multifunctional composite material comprises a polymeric matrix filled with electrically conductive nanoparticles combined with a self-healing molecular filler selected in the group consisting of molecules and oligomers containing groups acting as donors and acceptors of hydrogen bonds
MULTIFUNCTIONAL SELF-HEALING COMPOSITE MATERIAL FOR AERONAUTICS APPLICATIONS
No full textThe multifunctional composite material comprises a polymeric matrix filled with electrically conductive nanoparticles combined with a self-healing molecular filler selected in the group consisting of molecules and oligomers containing groups acting as donors and acceptors of hydrogen bonds
Seismic performance of historic masonry buildings: A comparative analysis of equivalent frame and block-based methods
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