Relationships Between LRI Process Parameters and Impact and Post-Impact Behaviour of Stitched and Unstitched NCF Laminates

The general context of the development of out-of-autoclave processes in the aeronautics industry raises the question of the possible links between these new processes and impact behaviour. In this study, a Taguchi table was used in a design of experiment approach to establish possible links. The study focused on the liquid resin infusion process applied to laminates made with stitched or unstitched quadri-axial carbon Non-Crimp Fabric (NCF). On the basis of previous studies and an analysis of the literature, five process parameters were selected (stitching, curing temperature, preform position, number of highly porous media, vacuum level). The impact energy was set at 35?J in order to obtain enough residual dent depth. The parameters analysed during and after impact were: maximum displacement of the impactor, energy absorbed, permanent indentation depth, and delaminated surface. Then, compression after impact tests were performed and the corresponding average stress was measured. The interactions found by statistical analysis show a very high sensitivity to stitching, which was, of course, expected. A very significant influence of curing temperature and a significant influence of preform position were also found on the permanent indentation depth and a physical explanation is provided. Globally, it was demonstrated that the resin infusion process itself did not influence the impact behaviour.     

Spin Diffusion Measurements in Spin-Polarised Liquid 3He-4He Mixtures

We report on investigations of spin diffusion in isotopic helium liquid mixtures using a multi-echo technique in applied magnetic field gradients. Samples (up to 1 cm ³ in volume) are obtained by liquefaction of optically polarised gas. NMR measurements are performed at saturated vapour pressure in a low magnetic field (2.2 mT). Signal-to-noise ratios stay high down to ³ He concentrations of order a few parts per thousand at 1K for instance. We demonstrate that the experimental accuracy of spin diffusion measurements is substantially improved using optically polarised mixtures. We have observed that the dynamics of the precession of the transverse magnetisation can be altered due to large dipolar fields at high magnetisation densities. Effects on spin-echo signals and implications for the extension of spin diffusion measurements with our technique are discussed.     

Modelisation de l'evolution du parathion dans le milieu naturel sur un pilote de laboratoireModelling parathion changes in the natural environment laboratory experiment

The evolution of parathion in a river, and its degradation by the principal natural factors (hydrolysis, photochemical oxidation, biological transformations and retention by sludge and sediments) has been studied on a laboratory pilot plant. The experimental period was 55 days. On the first 34 days, the plant was fed with a solution containing 13 mg l^?1 of the pesticide, and during the following 21 days, the effluent was continuously recycled.In the condition in which our experiences were conducted, the main phenomena were biological degradation of the pesticide into non poisonous amino-parathion and its adsorption on the sediments. The quantity of the parathion reduced is proportionated to the quantity of the ATP found in the activated sludge tank.This biological method being the more important, the shock effect of the parathion on a bacterial population was studied by varying the organo-phosphorous concentration (5-10-15 mg l^?1) and the quantity of volatile suspended solid (1-2-3 mg l^?1).The microorganisms were not affected by the poison and a reduction to aminoparathion was obtained. The quantitative results may be expressed by the following equation

$\text{? d(parathion)}\text{dt}\text{=K(ATP) (parathion).}$

On the other hand a very large dose of parathion (1 mg l^?1) destroyed the living organism.The presence of anionic or cationic surfactant plays no part in the toxicity of the parathion (15 mg l^?1) on the biomass but the degradation of the organo-phosphorous pesticide is totally inhibited.     

Detection and three-dimensional localization by stereoscopic visual sensor and its application to a robot for picking asparagus

This paper describes a three-dimensional localization process used on an agricultural robot designed to pick white asparagus. The system uses two cameras (CCD and Newvicon).Thanks to diascopic lighting, the images can easily be binarized. The threshold of digitalization is determined automatically by the system. A statistical study of the different shapes of asparagus tips allowed us to determine certain discriminating parameters to detect the tips as they appear on the silhouette of the mound of earth.The localization is done stereometrically with two cameras. As the robot carrying the system moves, the images are altered and decision criteria modified. A study of the images from mobile objects produced by both tube and CCD cameras was carried out. A simulation of this phenomenon has been done to determine the modifications concerning object shapes, thresholding levels and decision parameters as a function of robot speed.     

Hemangiopericytoma: a 20-year single-institution experience

In this overview, which is based on selected books and reviews, the microscopic appearances of prosthesis-bone interfaces resulting from clinically relevant implantation techniques are highlighted. The following techniques are distinguished to insert and attach prostheses in the recipient bone: impaction into bone, primary mechanical interlocking, cement fixation, bone ongrowth and secondary mechanical interlocking with bioinert materials, and enhanced bone ongrowth and bone bonding to bioactive materials. The resulting typical histomorphologies of orthopedic and dental prostheses-bone interfaces are described and illustrated from the author's studies employing light, fluorescence, and backscattered electron microscopy, and corresponding microradiographs of undecalcified ground sections of bone and implants. Special emphasis is given to the mineralization-demineralization kinetics of the interfacial bone matrix interacting with specific surface reactions of some implant materials. Consequently, the distinction between bioinert and bioactive prosthetic materials is critically analyzed.     

Endogenous superallergen protein Fv induces IL-4 secretion from human Fc epsilon RI+ cells through interaction with the VH3 region of IgE

We investigated the mechanism whereby protein Fv (pFv), a human sialoprotein found in normal liver and largely released in the intestinal tract in patients with viral hepatitis, induces mediator release from basophils and mast cells and evaluated whether it also induces IL-4 synthesis and secretion in basophils. pFv is a potent stimulus for histamine and IL-4 release from purified basophils. Histamine and IL-4 secretion from basophils activated by pFv was significantly correlated (rs = 0.70; p < 0.001). There was also a correlation (rs = 0.58; p < 0.01) between the maximum pFv- and anti-IgE-induced IL-4 release from basophils. The average t1/2 for pFv-induced histamine release was lower (3.5+/-1.5 min) than for IL-4 release (79.5+/-8.5 min; p < 0.01). IL-4 mRNA, constitutively present in basophils, was increased after stimulation by pFv and was inhibited by cyclosporin A and tacrolimus. Basophils from which IgE had been dissociated by brief exposure to lactic acid no longer released IL-4 in response to pFv and anti-IgE. The response to an mAb cross-linking the alpha-chain of Fc epsilon RI was unaffected by this treatment. Three human VH3+ monoclonal IgM concentration-dependently inhibited pFv-induced secretion of IL-4 and histamine from basophils and of histamine from human lung mast cells. In contrast, VH6+ monoclonal IgM did not inhibit the release of IL-4 and histamine induced by pFv. These results indicate that pFv, which acts as an endogenous superallergen, interacts with the VH3 domain of IgE to induce the synthesis and release of IL-4 from human Fc epsilon RI+ cells.     

Influence of chelating agents on the tribocorrosion of tungsten in sulphuric acid solution

The corrosion and tribocorrosion of tungsten in 0.01 M H₂SO₄, without and with the presence of lactic acid and phosphoric acid as chelating agents was studied here.The passive behaviour was characterised using potentiostatic polarization and potential step techniques combined with rotating disk electrodes. Surface analysis techniques (XPS, AES) were used to assess surface chemistry. The tribocorrosion of tungsten was investigated using a tribometer equipped with an electrochemical cell operating at applied passive potentials of 0.2 V and 1.0 V.Under static corrosion conditions chelating agents were found to enhance passive film dissolution and to decrease the passive film thickness. Despite this, the effect of the investigated chelating agents was limited under tribocorrosion conditions. Indeed, only lactic acid at the most anodic potential lead to significant differences in material removal by impeding the formation of protective tungsten oxide tribolayers. The discrepancy on the effect of chelating agents in corrosion and tribocorrosion was explained in terms of the different involved time constants.     

Electrostrictive polymer harvesting using a nonlinear approach

This paper presents a new application of the ‘synchronized switch harvesting on inductor’ (SSHI) applied to electrostrictive polymers for DC energy harvesting. It is demonstrated that this technique is very effective for harvesting energy from ambient vibrations using electrostrictive polymers. The method consists in adding an electrical switching device connected in parallel with the electrostrictive elements. The switch triggers on maxima or minima of the voltage and realizes a voltage inversion through an inductor. It is shown that, when applied to electrostrictive polymers, the SSHI technique increases the harvesting process efficiency by 700% compared to the classical approach.     

Influence of woven ply degradation on fatigue crack growth in thin notched composites under tensile loading

This paper deals with the fatigue of the through-the-thickness crack propagation in thin notched composite laminates made of two glass woven plies. It highlights the different crack growths between warp and weft directions of the woven ply. Experimental results show a decrease of the crack growth rate per cycle with the increase of the crack initiation time. Moreover, it has been shown that it is necessary to take into account the fatigue damage of the woven plies in term of loss of rigidity in the initiation phase. The fatigue crack growth rates are then quantified using Paris law type equations and linear elastic fracture mechanics (LEFM).     

Fabrication and mechanical testing of glass fiber entangled sandwich beams: A comparison with honeycomb and foam sandwich beams

The aim of this paper is the fabrication and mechanical testing of entangled sandwich beam specimens and the comparison of their results with standard sandwich specimens with honeycomb and foam as core materials. The entangled sandwich specimens have glass fiber cores and glass woven fabric as skin materials. The tested glass fiber entangled sandwich beams possess low compressive and shear modulus as compared to honeycomb and foam sandwich beams of the same specifications. Although the entangled sandwich beams are heavier than the honeycomb and foam sandwich beams, the vibration tests show that the entangled sandwich beams possess higher damping ratios and low vibratory levels as compared to honeycomb and foam sandwich beams, making them suitable for vibro-acoustic applications where structural strength is of secondary importance, e.g., internal paneling of a helicopter.