Adult and Egg Mortality of Rhynchophorus Ferrugineus Oliver (Coleoptera: Curculionidae) Induced by Thiamethoxam and Clothianidin.

The red palm weevil (RPW) is the major pest of palms in the Mediterranean region. One of the most interesting control solutions for this pest is endotherapy, comprising injections of biologically active substances directly into the stem of the palm. The objective of the present work was to study the ovicidal and adulticidal properties of two neonicotinoid insecticides (clothianidin and thiamethoxam) under laboratory conditions, to obtain evidence for application of endotherapy in the control of RPW infestations. Our results show that both commercial compounds display a dose-dependent action and exhibit different modes of action: clothianidin is more rapid in its action, but in general is less effective for control of the adult stages, while thiamethoxam is more effective, but its action requires longer to show efficacy. The eggs are much less sensitive to treatments, especially for clothianidin

Damage evolution in fuselage stiffened composite panels under asymmetrical bending loading conditions

In this paper, the damage mechanisms of reinforced composite panels subjected to symmetrical and asymmetrical flexural loading conditions have been investigated. The composite components are representative of a regional aircraft fuselage. Three-point bending tests numerical simulations have been used to assess the influence of the different test parameters on the damage behavior of the investigated component. Then, the most representative configuration has been selected for the experimental bending test. the outputs from the numerical simulations, in terms of stiffness and damage onset and propagation, has been employed, in combination with the experimental data, to accurately describe the damage mechanisms associated to the asymmetric application of the load

Numerical, Experimental and Analytical Correlation for Predicting the Structural Behavior of Composite Structures under Impact

Abstract In the present work, numerical, experimental and analytical results regarding impact events on composite structure are presented. The test case consists in a classic 24 plies CAI specimen (100×150 mm) subjected to 10 J impact. The work can be divided into two phases. The first phase is finalized to the definition of a procedure able to provide a robust numerical model, which can simulate accurately the structural response of composite plates subjected to impact events. At this phase, the numerical results are compared with analytical ones. In the second phase, both inter- and intra-lamina failure are considered. Regarding the inter-laminar failure, an experimental-numerical procedure is defined in order to set the right parameters related to cohesive behaviour. For both phases, trade-off analyses on the main numerical parameters are performed. All numerical results are compared with experimental ones in terms of both energy balance and damaged area

fuselage crashworthiness lower lobe dynamic test

Abstract The focus of this paper is to demonstrate the energy absorption capability of the lower lobe section of the aircraft, and to provide test data in support of validation of the LS-DYNA numerical model. Following a national research program, a full scale drop test, of an airliner composite sub cargo floor fuselage, has been performed by the Italian Aerospace Research Center (CIRA) at their LISA (Laboratory for Impact testing of Structures in Aerospace field) facility. The ultimate aims of research are design, size and evaluation of the crash behaviour of a specific concept of composite aircraft fuselage section linked to the full scale tests. The results are based on pre-test simulations performed on coupon including representative elements devoted to the absorbption of the crash energy, and finally with the final drop test results and the corresponding post-test simulations. Test provides validation of LS-DYNA analysis, and using the simulation tools it is possible to quantify different parameters as energy distribution, accelerations, dynamic structural efficiency, and structural deformations throughout the crash event, but above all the importance to define the real conditions of the constraints and loads in the attempt to reproduce the behaviour of the full scale aircraft fuselage, or section of it, during an emergency landing condition, partially reduced to the full scale subfloor. Then the simulation allows to develop geometries and size of the structures with stanchions and other structural elements in order to reduce the energy absorbing capabilities of the cargo subfloor. Test data indicates the cargo subfloor can absorb an impact velocity of 22 feet/sec with typical payload, and the certification requirements about the emergency landing as satisfied. Finally, the decelerations and deformations are restricted in a survivable space for the passenger compartment

Design of Composite Stanchions for the Cargo Subfloor Structure of a Civil Aircraft

Abstract The present work was performed in the frame of a national research program focused on the development of analysis method able to improve the structural response of civil aircraft subject to crash event. In particular, the aim of the program is to demonstrate the energy absorption capability of the lower lobe section of the fuselage aircraft. One of principal substructures, which is able to absorb the impact energy in a crash event, is the cargo subfloor. In this work, the results obtained by an experimental test campaign on cargo subfloor elements are presented. The test case consists in a full scale composite stanchion. The experimental results were used to provide information useful to set the numerical models. Indeed, setting and calibrating the numerical models is an important point in order to have useful tools able to improve the absorption energy capability by means of optimization analyses. The stanchion was tested under static and dynamic load conditions, at different impact energy levels

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

Drop test simulation and validation of a full composite fuselage section of a regional aircraft

Abstract In the aircraft industry, the use of fiber reinforced materials for primary structural components over metallic parts has increased up to more than 50% in the recent years, because of their high strength and high modulus to weight ratios, high fatigue and corrosion resistance. Currently, the need of lowering weight and fuel consumption is pushing the world's largest aircraft manufacturers in the design and building of structures entirely made of composites. Fuselage structure plays an important role in absorbing the kinetic energy during a crash. Through the deformation, crushing and damage of fuselage sub-floor structure, a survivable space inside the cabin area should be preserved during and after a crash impact in order to minimize the risk of passengers' injuries. In this work, a Finite Element (FE) model of a full-scale 95% composites made fuselage section of a regional aircraft under vertical drop test is presented. The experiment, conducted by the Italian Aerospace Research Centre (CIRA) with an actual impact velocity of 9.14 m/s in according to the FAR/CS 25, has been numerically simulated. Two ATDs (Anthropomorphic Test Dummies), both 50th percentile, seats and belts have been modelled to reproduce the experimental setup. The results of the simulation, performed by using LS-DYNA® explicit FE code, have been validated by correlation with the experimental ones. Such comparisons highlight that a good agreement has been achieved. The presented FE model allows verifying the structural behavior under a dynamic load condition and also estimating the passive safety capabilities of the designed structure. Since the experiment is expensive and non-repeatable, a FE model can be used for Certification by Analysis purposes since, if established, it is able to virtually demonstrate the compliance to the airworthiness rules

Correlation between real geometry and tensile mechanical behaviour for Ti6Al4V electron beam melted thin specimens

The Electron Beam Melting (EBM) is an Additive Layer Manufacturing (ALM) technique used to directly manufacture 3D functional parts from metal powder, selectively melted, layer by layer, by an electron beam according to a geometry defined by a CAD model. The EBM technology allows benefitting from countless advantages: material waste reduction, easy manufacturing of complex shapes, lead time reduction, etc; on the other hand the EBM process is typically associated with lower resolutions and higher surface roughness (Ra = 25–30 μm) compared to similar laser based powder bed metal processes. Therefore the surface morphology may be a critical issue for the structural integrity of components made in EBM and used in-service in their “as built” condition, i.e. with the characteristic surface released by the process. This study evaluates surface morphology and tensile properties of Ti6Al4V specimens of varying nominal thickness (1–5.0 mm), made by using EBM process with a layer thickness of 50 μm. The aim is therefore to investigate how the surface morphology and the tensile properties are affected by the nominal thickness of the component