Detection of debonding in composite-aluminum joints using gamma-ray Compton scattering

Gamma-ray Compton scattering is used for the detection of debonding in adhesively bonded composite-aluminum joints. A collimated narrow beam of monochromatic photons, generated by a ¹³⁷CS source, is directed towards the joint and scattered photons are recorded, using a detector located on the same side as the source. The energy of the scattered radiation is measured and related to the angle of scattering. The occurrence of debonding is indicated by a change in the count rate at an energy corresponding to its location. The performance of the technique is successfully demonstrated experimentally for joints of different adhesive-bonding thicknesses and for artificially induced debonds.     

ANALYSIS OF UNSTABLE BEHAVIOR OF PNEUMATIC CONVEYING SYSTEMS

The unstable conveying zone has been recognized by many authors in their attempts to define the minimum conveying velocitv on the dilute phase side of this zone. It was found that the gas flow rate influences the magnitude and frequency of the pressure fluctuations experienced during this type of flow. Generally a reduction of gas flow rate will reduce both the intensity and frequency of the fluctuations.

During the measurement of data for the previous experiments, it was recognized that the pressure fluctuations of dilute and strand flow can serve as simple indicators of the flow stability. An analysis of these fluctuations is presented, which suggests that simple statistical factors can be used to estimate the system condition of operation with respect to the pressure minimum or unstable zone. These elementary trends in the data can be useful for one attempting to optimize a system. This analysis lead to a more intensive approach using Hurst's rescaled range analysis, to examine the changes in pressure fluctuations, which occur when a system undergoes a simulated optimization procedure. The analysis suggested that Hurst's exponent may be used as an indicator of the onset of instability.     

Thermal stability and flammability studies of coated polymer powders using a plasma fluidized bed process

In this work, the thermal stability of organosilicon coatings, polyamide-6 powders and polyamide-6 clay nanocomposite powders coated with organosilicon are studied. The coatings were obtained from polymerization of 1.1.3.3-tetramethyldisiloxane (TMDS) monomer doped with oxygen using a cold remote nitrogen plasma (CRNP) process. A fluidized bed reactor using CRNP assisted polymerization was used to coat the polymer powders. The effect of oxygen addition to TMDS on the thermal stability was investigated. Oxygen addition to TMDS promotes the formation of more thermally stable coated polymers. In the case of the polyamide-6 clay nanocomposite, the Limiting Oxygen Index values were much improved. This shows that the deposits are effective fire retardant coatings.     

Adsorption properties and inhibition of mild steel corrosion in hydrochloric solution by some newly synthesized diamine derivatives: Experimental and theoretical investigations

New diamine derivatives, namely 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]ethanol (DAME) and 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]propanol (DAMP) were synthesised and their inhibitive action against the corrosion of mild steel in 1 M HCl solution were investigated at 308 K. The detailed study of DAME is given using gravimetric measurements and polarization curves method. Results show that DAME is a good inhibitor and inhibition efficiency reaches 91.7% at 10⁻³ M. Tafel polarization study revealed that DAME acts as a mixed-type inhibitor. The inhibitor adsorption process in mild steel/DAME/hydrochloric acid system was studied at different temperatures (308-353 K) by means of weight loss measurements. The adsorption of DAME on steel surface obeyed Langmuir’s adsorption isotherm. The kinetic and thermodynamic parameters for mild steel corrosion and inhibitor adsorption, respectively, were determined and discussed. The comparative study of inhibitive performance of the two diamine derivatives revealed that DAME is more effective than DAMP. Quantitative Structure-Activity Relationship (QSAR) approach has been conducted in attempt to correlate the corrosion inhibition properties of these diamine derivatives with their calculated quantum chemical parameters.     

Study of nisin adsorption on plasma-treated polymer surfaces for setting up materials with antibacterial properties

Setting up antibacterial materials by nisin adsorption on surfaces depends mainly on the surface properties and the surface treatments allowing the modification of such properties. In order to investigate the factors affecting such adsorption, the native low density polyethylene (LDPE) was modified using Argon/Oxygen (Ar/O₂) plasma, nitrogen (N₂) plasma and plasma-induced grafting of acrylic acid (AA). The films were studied by various characterization techniques. The chemical surface modification was confirmed by X-ray photoelectron spectroscopy (XPS), the wettability of the surfaces was evaluated by contact angle measurements, the surface charge was determined by the zeta potential measurements, and the changes in surface topography and roughness were revealed by atomic force microscopy (AFM). Nisin was adsorbed on the native and the modified surfaces. The antibacterial activity, the nisin adsorbed amount, and the peptide distribution were compared for the four nisin-functionalized films. The highest antibacterial activity was recorded on the Ar/O₂ followed by AA then by N₂ treated films and the lowest activity was on the native film. The observed antibacterial activity was correlated to the type of the surface, hydrophobic and hydrophilic interactions, surface charge, surface topography, nisin adsorbed amount, and nisin distribution on the surfaces.     

Energy absorbing characteristics of aluminium beams strengthened with CFRP subjected to transverse blast load

Carbon fibre-reinforced polymer (CFRP) strengthening of structures has been gaining increasing interest, traditionally applied to concrete structures, and more recently applied to metal structures. Epoxy bonding of carbon fibre to metal has been successfully employed for strengthening structures loaded under static and impact loads. In this paper the metal–fibre bond is investigated under impulsive loads by the application of explosives to fully clamped solid aluminium beams. It is shown that the use of bonded CFRP to metal structures that undergo large plastic deformations is advantageous, since the full strength of the carbon fibres is utilised as a result of the large strain field produced by the plastic deformation in the metal. The experimental results show that a significant amount of energy may be absorbed by the layer of carbon fibres bonded directly to the metal, however subsequent carbon fibre layers suffer from interlaminar debonding mechanisms as a result of shock spalling that reduce their efficiency. A theoretical method is developed whereby the energy absorbed by the carbon fibres may be determined, and the remaining explosive energy is absorbed by the plastic deformation of the metal. Fibre efficiency factors for multiple fibre layers and dynamic effects are introduced and are shown to produce reasonable agreement with the test results.     

Surface Functionalization with Phosphazenes: Part 6. Modification of Polyethylene-Co-Polyvinylalcohol Copolymer Surface Plates with Fluorinated Alcohols and Azobenzene Derivatives Using Chlorinated Phosphazenes as Coupling Agents

In this paper we describe a two-step surface modification process of poly(ethylene-co-vinyl alcohol) by exploiting hexachlorocyclophosphazene and poly(dichlorophosphazene) as coupling agents. Part of the P–Cl groups of the chlorophosphazenes is first reacted with the surface hydroxylic groups of the substrate to form covalent P–O–C bonds, the remaining being utilized for successive substitution reactions with different nucleophiles (i.e. 2,2,2-trifluoroethanol, heptadecafluorononanol and 4-hydroxyazobenzene). Modified surface properties, such as hydrophobicity improvement with fluorinated alcohols and photochromic features with the azobenzene derivative, were verified by contact angle measurements and UV–Vis spectroscopy, respectively, while changes in surface composition were demonstrated through XPS spectroscopy.     

Surface functionalization with phosphazenes. V. Surface modification of plasma-treated polyamide 6 with fluorinated alcohols and azobenzene derivatives through chlorinated phosphazene intermediates

In this article, we describe the synthesis and characterization of surface-modified polyamide-6, using polydichlorophosphazene and hexachlorocyclophosphazene as coupling agents. The solid surface of this polymer was modified first by the introduction of polar functions (CO, OH, OR, COOH, COOR, etc.) with a cold plasma technique, then by the treatment of the alcoholic groups on the surface with (NPCl₂)_n and (NPCl₂)₃ to graft these substrates through the formation of strong covalent P O C bonds, and eventually by the substitution of the residual chlorines on the polyamide-6 surface with different types of fluorinated alcohols (2,2,2-trifluoroethanol and heptadecafluorononanol) and with 4-hydroxyazobenzene. Contact-angle measurements, together with X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy techniques, support the occurrence of these surface-functionalization reactions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The drivers of consumers’ intention to redeem a push mobile coupon

A modern-day marketing tool that has caught the industry's attention is the use of mobile coupons (m-coupons). Despite the attractiveness of this new marketing tool, a high level of consumer resistance is reported. To therefore ensure the successful implementation of an m-coupon strategy, customer buy-in is a prerequisite. The research on which this article is based, aimed to explore the factors that contribute to consumers’ intention to ultimately redeem m-coupons. A hypothesised model proposes economic benefit, convenience benefit, positive consumer attitude, perceived control and social benefit as constructs that either directly or indirectly influence consumers’ intention to redeem an m-coupon. A survey of 204 respondents revealed that a consumer's positive attitude is the main driving force behind m-coupon redemption intentions. Results reflected that businesses should emphasise convenience and economic benefits in order to assist in the development of a positive attitude amongst potential m-coupon users. Consumers value their privacy and are resistant towards push-based m-coupons. If businesses incorporate these aspects into their m-couponing strategy, it will allow them to reach their audience in an entirely new manner and in doing so, potentially trigger purchase behaviour or increase store foot count.     

Essential Oil of Salvia officinalis as Novel Eco-Friendly Inhibitor for Carbon Steel in HCl Solution: Weight Loss,Electrochemical and XPS Studies

Protection of Metals and Physical Chemistry of Surfaces - Essential oil of a medicinal plant (Salvia officinalis), used as an eco-friendly inhibitor for the corrosion of carbon steel in 1 M HCl, is...