Dynamic pulse buckling of composite stanchions in the sub-cargo floor area of a civil regional aircraft

This work is focused on the investigation of the structural behavior of a composite floor beam, located in the cargo zone of a civil aircraft, subjected to cyclical low-frequency compressive loads with different amplitudes. In the first stage, the numerical models able to correctly simulate the investigated phenomenon have been defined. Different analyses have been performed, aimed to an exhaustive evaluation of the structural behavior of the test article. In particular, implicit and explicit analyses have been considered to preliminary assess the capabilities of the numerical model. Then, explicit non-linear analyses under time-dependent loads have been considered, to predict the behavior of the composite structure under cyclic loading conditions. According to the present investigation, low-frequency cyclic loads with peak values lower than the static buckling load value are not capable of triggering significant instability

A sensitivity analysis of the damage behavior of a leading-edge subject to bird strike

This paper aims to investigate the crashworthiness capability of a commercial aircraft metallic sandwich leading edge, subjected to bird strike events. A sensitivity analysis is presented, aimed to assess the influence of the skin parameters (inner and outer faces and core thicknesses) on the leading-edge crashworthiness and to determine, among the configurations able to withstand a bird strike event, the best compromise in terms of weight and structural performances. In order to easily manage the design parameters and the output data, the ModeFrontier code was used in conjunction with the FE code Abaqus/Explicit. A dedicated python routine was developed to define a fully parametric simplified leading-edge model. To fulfill the aerodynamic requirements, the external surfaces were considered fixed during the sensitivity analysis, and, thus, only the internal leading edge’s components were modified to study their influence on the structural response. The total mass of the model, the maximum deformation and the energy dissipated due to material failure and the plastic deformations were monitored and used to compare and assess the behavior of each configuration

Numerical-experimental investigation into the tensile behavior of a hybrid metallic-CFRP stiffened aeronautical panel

In this work, the tensile behavior of a hybrid metallic-composite stiffened panel is investigated. The analyzed structure consists of an omega-reinforced composite fiber-reinforced plastic (CFRP) panel joined with a Z-reinforced aluminum plate by fasteners. The introduced numerical model, able to simulate geometrical and material non-linearities, has been preliminary validated by means of comparisons with experimental test results, in terms of strain distributions in both composite and metallic sub-components. Subsequently, the inter-laminar damage behavior of the investigated hybrid structure has been studied numerically by assessing the influence of key structural subcomponents on the damage evolution of an artificial initial debonding between the composite skin and stringers

Left ventricular (LV) pacing in newborns and infants. Echo assessment of LV systolic function and synchrony at 5-year follow-up

Background: Small retrospective studies reported that left ventricular (LV) pacing is likely to preserve LV function in children with isolated congenital complete atrioventricular block (CCAVB). The aim of this study was to prospectively evaluate LV contractility and synchrony in a cohort of neonates/infants at pacemaker implantation and follow-up. Methods: Patients with CCAVB who underwent LV pacing were evaluated with electrocardiogram and echocardiogram in a single-center, prospective study. Data were collected at implantation, at 1-month and every year of follow-up, up to 5 years. LV ventricular dimensions (diameters and volumes), systolic function (ejection fraction [EF] and global longitudinal strain [GLS]), and synchrony were evaluated. Data are reported as median (25th-75th centiles). Results: Twenty consecutive patients with CCAVB underwent pacemaker implantation (12 single-chamber pacemaker [VVIR] and eight dual-chamber pacemaker [DDD]) with epicardial leads: 17 on the LV apex and three on the free wall. Age at implantation was 0.3 months (1 day-4.5 months). Patients showed good clinical status, normal LV dimensions, preserved systolic function, and synchrony at 60 (30-60) months follow-up. EF increased to normal values in patients with preimplantation EF <50%. Presence of antibodies and pacing mode (DDD vs VVIR) had no impact on the outcome. Conclusions: LV pacing preserved LV systolic function and synchrony in neonates and infants with CCAVB at 5-year follow-up. LV EF improved in patients with low preimplantation EF. Pacing mode or the presence of autoantibodies did not demonstrated an impact on LV contractility and synchrony

Business for Ocean Sustainability

Peer reviewe

Business for ocean sustainability: Early responses of ocean governance in the private sector

Este artículo contiene 18 páginas, 2 tablas, 6 figuras.A large sample of 1664 companies—69 directly working in the ocean economy—distributed across 19 industrial sectors was investigated to explore awareness and activation regarding direct and indirect pressures on the ocean, their responses to these pressures, and the disclosure tools used. We examined their accountability and disclosure practices on sustainable development goals (SDGs) using the drivers, pressures, state, welfare, and response accounting framework. Based on their 2019 sustainability reports, just 7% of the companies assessed disclosed on SDG14. However, 51% of these companies can be considered as aware, albeit to varying degrees, of the pressures their industries place on the oceans, 44% deploy mitigating activities, and 26% are aware and actively lead business responses to ocean challenges. Although we have seen just early responses in addressing ocean challenges, companies’ awareness and activation must converge to achieve ocean sustainability and move businesses into a truly blue economy.This research was funded by the One Ocean Foundation (www.1ocean.org), as part of its commitment to the research and diffusion of ocean literacy. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Peer reviewe

Numerical-Experimental Correlation of Interlaminar Damage Growth in Composite Structures: Setting Cohesive Zone Model Parameters

Composite laminates are characterized by high mechanical in-plane properties while experiencing, on the contrary, a poor out-of-plane response. The composite laminates, indeed, are often highly vulnerable to interlaminar damages, also called "delaminations." One of the main techniques used for the numerical prediction of interlaminar damage onset and growth is the cohesive zone model (CZM). However, this approach is characterised by uncertainties in the definition of the parameters needed for the implementation of the cohesive behaviour in the numerical software. To overcome this issue, in the present paper, a numerical-experimental procedure for the calibration of material parameters governing the mechanical behaviour of CZM based on cohesive surface and cohesive element approaches is presented. Indeed, by comparing the results obtained from the double cantilever beam (DCB) and end-notched flexure (ENF) experimental tests with the corresponding numerical results, it has been possible to accurately calibrate the parameters of the numerical models needed to simulate the delamination growth phenomenon at coupon level

A numerical assessment on the influences of material toughness on the crashworthiness of a composite fuselage barrel

In the present work, a numerical study on the dynamic response of a composite fuselage barrel, in relation to crashworthiness, has been investigated. The aim of this work is to investigate the influence of the material fracture toughness on the capability of a composite fuselage barrel to tolerate an impact on a rigid surface. Three different material configurations with different intra-laminar fracture energy values were considered to take into account variations in material toughness. Indeed, the dynamic behaviour of the analysed fuselage barrel has been numerically simulated by means of the FE (Finite Element) code Abaqus/Explicit. The effects of intralaminar fracture energy variations on the impact deformation of the barrel has been evaluated comparing the numerical results in terms of displacements and damage evolution for the three analysed material configurations

ON THE DYNAMIC RESPONSE OF A COMPOSITE FUSELAGE SUB-FLOOR SUPPORT SYSTEM

In this work, the dynamic response, including damage onmset and evolution, of the composite floor subsection of the cargo area of a civil aircraft is investigated by numerical simulations and experimental tests. The analysed structure has been subjected to impacts characterized by different energies, after a preliminary quasi-static mechanical test. Experimental data has been compared to numerical results in order to better understand and characterize the intra-laminar and inter-laminar damage onset and evolution. Preliminary quasi-static and dynamic numerical analyses have been carried out on a single subsection component to set up the numerical model in the ABAQUS FEM environment; then, in a subsequent phase, the entire structure has been numerically analysed focusing on the inter-laminar and intra-laminar damages onset and propagation. The correlation between numerical results and experimental data, with the aid of ultrasonic non destructive inspections output images, has been carried out