Crashworthiness optimization of aircraft hybrid energy absorbers enclosing honeycomb and foam structures

[Abstract:] This research proposes a new design for a vertical strut used in aircraft fuselages. It consists of a hollow aluminum vertical strut filled with a glass-fiber-reinforced polymer honeycomb-shaped structure and polymeric foam. The design is optimized for crashworthiness of aircraft fuselage structures. The variables of the surrogate-based optimization procedures are the thicknesses of the aluminum and polymer, and the cell size and shape. The objective functions for the single-objective optimization are the specific energy absorption and the cost, whereas the metrics for the multiobjective optimization are the two aforementioned along with the peak force, mass, and absorbed energy. By using the polymeric foam, an improvement of 28% on the specific energy absorption is obtained when compared to a component without this reinforcement. Compared to a baseline model, the optimum also reduces the cost by 40%. Three Pareto fronts are obtained with different combinations of objective functions. When compared to different baseline models, the optimized models show substantial improvement, increasing the specific energy absorption while reducing peak force, mass, and costs. An important effect of the cell shape on the model’s performance is observed, with the optimum models having pseudorectangular cells.Ministerio de Economía y Competitividad. MINECO; DPI2013-41893-R

Crashworthiness analysis and enhancement of aircraft structures under vertical impact scenarios

[Abstract:] This research focuses on the crashworthiness study and enhancement of commercial aircraft structures by developing crushable energy absorbers to work as vertical struts. To assess their contribution on a representative crash scenario, a numerical simulation of a Boeing 737-200 drop test developed and verified with experimental data is used as a benchmark. The numerical model is then enhanced with four hybrid energy absorbers designed for programmed and progressive collapse, added in the cargo compartment connecting the underfloor beams and the frames. These devices are composed of a square aluminum tube filled with a composite skeleton and foam extrusions for maximized energy absorption. The enhanced aircraft is later on simulated under hard landing and water ditching scenarios, analyzing the benefits resulting from the absorbers according to structural efficiency and biometric criteria. Results show increased plastic dissipation values by the main structural components given the modified collapse mechanism obtained when adding the crushable absorbers. Peak acceleration values are also reduced, consequently lessening the passenger injury prediction at the studied locations.Ministerio de Economa y Competitividad; DPI2016-76934-RMinisterio de Economía y Competitividad; DPI2016-76934-

Crushing analysis and multi-objective crashworthiness optimization of GFRP honeycomb-filled energy absorption devices

[Abstract:] Fuel efficiency and occupant safety are two of the most important concerns in the automotive industry nowadays. Encouraged by the importance of this field of study, this research attempts an improvement in the crashworthiness of a vehicle crash absorber. This component consists in a square hollow steel tube filled with a honeycomb structure made of glass-fiber reinforced polyamide. Surrogate-based optimization techniques are used. The three objective functions chosen — mass, absorbed energy and peak load — are approximated by two different models: multivariate adaptive regression splines and Gaussian process (kriging). The thickness of both parts, the shape of the honeycomb and its height are selected as design variables. Two preliminary analyses of the specimen are performed: the computation of the interaction effect and a comparison of a hollow tube with the specimen. From the results of multi-objective crashworthiness optimization two Pareto frontiers are obtained, one for the absorbed energy and mass, and another one for the absorbed energy and peak load. The results achieved show great improvements on all objective functions compared to the original design. The peak load is reduced by 37% on a specimen with similar mass and absorbed energy, and the specific energy absorbed is increased by 39.5% for a specimen with a similar peak load to the one from the initial model.Xunta de Galicia. INCITE09; 09DPI01118PRXunta de Galicia. INCITE09; GRC2013-05

Size and shape optimization of aluminum tubes with GFRP honeycomb reinforcements for crashworthy aircraft structures

[Abstract:] Crashworthiness optimization of aircraft and automotive structures has become one the main research targets for their respective leading industries. The following research proposes a new design of an aircraft’s vertical strut. The design consists of a hollow aluminum square tube with a glass-fiber reinforced polymer honeycomb-shaped inner structure. Size and shape surrogate-based optimization techniques are used, with the thicknesses of both materials, cell size and cell shape as design variables. The objective function chosen for the single-objective optimization is the specific energy absorption, while the metrics for the multi-objective optimization are the peak force, mass, absorbed energy and the specific energy absorption. An improvement of 22% of the specific energy absorption with low peak force values is obtained from the single-objective optimization by significantly changing all design variables. Two Pareto fronts have been obtained from the multi-objective optimization confronting, the specific energy absorption against the peak force and the mass against the energy absorbed. When compared to the baseline model, the optimized models show substantial improvement, increasing the specific energy absorption by 65% or reducing the peak force by over 55%. It has been observed an important effect of the cell shape on the model’s performance.Ministerio de Economía y Competitividad. MINECO; DPI2013-41893-

A conceptual approach to the tourist value co-creation:Dimensions, antecedents and consequences

In the last decades, several studies related to the Service-Dominant Logic approach were carried out, where the tourism industry is not an exception. As such, multiple works associated with this research stream have been developed, with a special focus on the tourist value co-creation. This article presents a conceptual model that aims to aggregate the various dimensions of customer value co-creation with its antecedent and consequent factors in the tourism industry. On the other hand, it proposes practical implications for the tourist organizations building on conceptual contributions. Thus, this article reveals the importance of other constructs of tourist value cocreation which surpass the behavioral dimension of the customer, namely, attitude, significance and recognition. Furthermore, this study systematizes the multiplicity of antecedent and consequent factors, recognizing that they may be grouped into factors associated to the company as well as to the customer.8316-FD77-85EB | Pedro Miguel Fonseca Moreira de Carvalhoinfo:eu-repo/semantics/publishedVersio

Energy Absorption of Aluminium Extrusions Filled with Cellular Materials Under Axial Crushing: Study of the Interaction Effect

Artigo publicado no número especial Armour and Protection Systems: https://www.mdpi.com/journal/applsci/special_issues/Armour_Protection_System[Abstract] This investigation focuses on the interaction effect during the quasi-static axial crushing of circular and square thin-walled aluminium extrusions filled with polymeric foam or cork. The increment in the absorbed energy due to interactions between materials was assessed using a validated numerical model calibrated with experimental material data. Simulations were run with variable cross-section dimensions, thickness, and foam density. The results were used to adjust the parameters of design formulas to predict the average crush forces of foam- and cork-filled thin-walled tubes. The analysis of the energy dissipation per unit volume revealed that the highest increments due to the interaction between materials appeared in the foam-filled square extrusions. Energy dissipation increased with higher density foams for both cross-sections due to a stronger constraint of the aluminium walls, and thus a reduction of the folding length. Thinner tube walls also delivered a higher improvement in the energy dissipation per unit volume than those with thicker walls. The contribution of friction was also quantified and investigated.This research was funded by the Spanish Goverment (Ministerio de Economía y Competitividad) grant number PID2019-108307RB-I00; and from the Research Council of Norway grant number 237885, SFI-CASA, and NTNUResearch Council of Norway; 237885https://www.mdpi.com/journal/applsci/special_issues/Armour_Protection_Syste

The influence of copolymer composition on PLGA/nHA scaffolds´ cytotoxicity and in vitro degradation

The influence of copolymer composition on Poly(Lactide-co-Glycolide)/ nanohydroxyapatite (PLGA/nHA) composite scaffolds is studied in the context of bone tissue engineering and regenerative medicine. The composite scaffolds are fabricated by thermally-induced phase separation and the effect of bioactive nanoparticles on their in vitro degradation in phosphate-buffered solution at 37 °C is analyzed over eight weeks. The indirect cytotoxicity evaluation of the samples followed an adaptation of the ISO 10993-5 standard test method. Based on the measurement of their molecular weight, molar mass, pH, water absorption and dimensions, the porous scaffolds of PLGA with a lower lactide/glycolide (LA/GA) molar ratio degraded faster due to their higher hydrophilicity. All of the samples without and with HA are not cytotoxic, demonstrating their potential for tissue engineering applications.SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is really appreciated. This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013 and Grant SFRH/BD/111478/2015 (S.R). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (Agencia Estatal de Investigación(AEI)/FEDER, Unión Europea(UE))info:eu-repo/semantics/publishedVersio