Filament Winding of Co-Extruded Polypropylene Tapes for Fully Recyclable All-Polypropylene Composite Products

The creation of high-strength co-extruded polypropylene (PP) tapes allows the production of recyclable “all-polypropylene” (all-PP) composite products, with a large temperature processing window and a high fibre volume fraction. Available technologies for all-PP composites are mostly based on manufacturing processes such as thermoforming of pre-consolidated sheets. The objective of this research is to assess the potential of filament winding as a manufacturing process for all-PP composites made directly from co-extruded tapes or woven fabric. Filament wound pipes or rings were tested either by the split-disk method or a hydrostatic pressure test in order to determine the hoop properties, while an optical strain mapping system was used to measure the deformation of the pipe surfaces.     

Acid corrosion analysis of fibre glass

The scanning electron microscope and the energy dispersive X-ray based analytical techniques have been used to study the sulphuric acid corrosion resistance of standard “E” fibre glass and PPG developed and patented 1201 [1], an “ECR” acid-resistant fibre glass. While it is well agreed by the experts in the field that direct exposure of fibre glass to 0.5 m sulphuric acid is much too severe a condition to simulate service conditions of most filament wound fibre glass products, nevertheless, the above corrosive environment was used to demonstrate a significant superiority of PPG 1201 glass in acid resistance over the standard “E” glass regardless of the source of its origin. It is also demonstrated that not only boron oxide leached out during acid exposure but a significant amout of calcium, aluminium, and magnesium oxides also were depleted from the “E” glass composition during acid treatment. It is also demonstrated that heat treatment of “E” glass products reduced the rate of acid attack. It did not, however, eliminate it completely. Heat treatment affects the strength properties of this fibre glass adversely.     

The Transfer of Fibres in the Carding Machine

The problem of understanding the transfer of fibres between carding-machine surfaces is addressed by considering the movement of a single fibre in an airflow. The structure of the aerodynamic flow field predicts how and when fibres migrate between the different process surfaces. In the case of a revolving-flats carding machine the theory predicts a “strong” aerodynamic mechanism between taker-in and cylinder and a “weak” mechanism between cylinder and removal cylinder resulting in effective transfer in the first case and a more limited transfer in the second.     

Estimate of incompleteness error of moisture absorption in coulometric hygrometers

One of the most important components of the error of flow-through coulomometric hygrometers is that due to “moisture transit,” or loss. Exact relationships between this error and the fraction of electrolytic current from the control part of a coulometric cell for both fresh (“new”) cells (i.e., those that been regenerated) and cells that are in the aging process are obtained. It is shown that it is possible to determine and take into account this error in the measurement process.     

Novel basalt fibre reinforced glass matrix composites

A novel hot-pressing technique for the manufacturing of basalt fibre reinforced glass matrix composites was investigated. Two-dimensional (2D) fibre mats were sandwiched between borosilicate glass powder layers, thus configuring a much simpler processing route than that commonly employed for the production of fibre-reinforced glasses. Besides economic benefits, the use of fibre mats may lead to technologic advantages due to the possibility of readily coating the fibres with a suitable material (e.g. titanium oxide) by means of the sol-gel method. The coating of basalt fibre mats with TiO₂ is proposed for preventing the fibres from an excessive adhesion to the glass matrix. The developed composites containing 15 vol% of 2D-fibre reinforcement exhibited promising bending strength (∼90 MPa) and desirable “graceful” fracture behaviour without catastrophic failure. Thus the present study represents a convenient approach for production of advanced low-cost fibre reinforced glass matrix composites for structural applications.     

Time dependencies of Bradford distributions: Structures of journal output in 20th-century logic and 19th-century mathematics

Time dependencies of Bradford distributions are investigated for 19th-century mathematics and for 20th-century logic. To facilitate comparisons, for the representation of empirical Bradford distributions “Pareto's law” and Lorenz diagrams are used. It is shown that the character of a Bradford distribution (including the “core zone” and the “Groos droop”) depends on the stage in the development of a scientific field and that it varies with the time-span considered.     

Garfield’s demon and “surprising” or “unexpected” results in science

The relative occurrence of the words “surprising” and “unexpected” in the titles of scientific papers was 11 times more common in 2001–2005 than in 1900–1955. However, papers which had titles containing one of these words did not receive enhanced numbers of citations. Both words (and also adjectives “unusual” and “unfortunately”) are used significantly more frequently in science than in social sciences and humanities. The distribution of the statements of surprise is not random in scientific literature (chemistry journals ranked highest in the number of papers claiming “surprising” or “unexpected” results) and may reflect the level of maturity of a discipline.     

Experimental studies on process-induced morphological characteristics of macro- and microstructures in laser consolidated alloys

Laser consolidation (LC) developed by National Research Council’s Industrial Materials Institute (NRC-IMI-London) since mid-1990s, is a laser cladding based rapid manufacturing and material additive process that could fabricate a “net-shape” functional metallic shape through a “layer-upon-layer” deposition directly from a computer aided design model without using molds or dies. In order to evaluate the LC processability of different materials, some representative nickel-based superalloys (IN-625, IN-718, IN-738, and Waspaloy), stainless steels (austenitic SS316L and martensitic SS420), and lightweight alloys (Ti–6Al–4V titanium alloy and Al-4047 aluminum alloy) have been investigated. Like other laser cladding based processes, due to process-induced rapid directional solidification, the LC alloys have demonstrated certain unique morphological characteristics. Moreover, the “as-consolidated” LC alloys, in nature, are in the “as-quenched” state, and some precipitation processes from their matrices, which are sometimes critical to the development of mechanical performance of the materials, could be effectively suppressed or retarded. Post-heat treatments, therefore, could necessarily facilitate the process of achieving their required operational microstructures. In this article, a comprehensive investigation was performed including metallurgical soundness and process-induced morphological characteristics of the LC materials, and microstructure development brought by post-LC heat treatments using optical microscope, scanning electron microscope, and X-ray diffraction. The implications on the mechanical performance of the LC materials were discussed as well in order to provide essential information for potential industrial applications of the LC materials.     

The study of lifetime of polymer and composite bone joint screws under cyclical loads and <Emphasis Type="Italic">in vitro</Emphasis> conditions

The “strain-life time” method has been adapted for life-time prediction of polymer and composite bone joint screws. Mechanical and fatigue properties of screws made of biostable (polysulfone), biosorbable (poly(lactide-co-glycolide) and short carbon fibre reinforced polymer composite materials have been examined in this study. The lifetime predictions under in vitro conditions were calculated for polymer and composite implants. The forecasting of joint screws stability under conditions close to natural body environment is shown to be feasible based on equations describing lifetime of the examined joint screws.     

Uncertainty of measurement results in various scales

The relationship between the concepts of “error” and “uncertainty” of measurement results is examined. The concepts of “standard uncertainty,” “combined standard uncertainty,” and “expanded uncertainty” are shown to be inapplicable in nonmetric scales of quantities and properties, in which the general concept of “uncertainty” in the broad sense is recommended. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 29–30, May, 2000.     

Rimming flows within a rotating horizontal cylinder: asymptotic analysis of the thin-film lubrication equations and stability of their solutions

It is well-known that a standard lubrication analysis of the equations of motion in thin liquid films coating the inside surface of a rotating horizontal cylinder leads, under creeping-flow conditions, to a cubic equation for the film thickness profile which, depending on the fluid properties of the liquid, the speed of rotation and the fill fraction F, has either (a) a continuous, symmetric (homogeneous) solution; (b) a solution containing a shock; or (c) no solution below a certain speed. By means of an asymptotic analysis of the recently proposed “modified lubrication equation” (MLE) [M. Tirumkudulu and A. Acrivos, Phys. Fluid 13 (2000) 14–19], it is shown that the solutions of the cubic equation referred to above correctly describe the film-thickness profiles although, when shocks are involved, under exceedingly restrictive conditions, typically F~ 10⁻³ or less. In addition, using the MLE, the linear stability of these film profiles is investigated and it is shown that: the “homogeneous” profiles are neutrally stable if surface-tension effects are neglected but, if the latter are retained, the films are asymptotically stable to two-dimensional disturbances and unstable to axial disturbances; on the other hand, the non-homogeneous profiles are always asymptotically stable, thus confirming results given earlier [T.B. Benjamin, W.G. Pritchard, and S.J. Tavener (preprint, 1993)] on the basis of the standard lubrication analysis.     

Evolution of the morphological structure of a two-dimensional cluster obtained with a linear microparticle trajectory in the diffusion-limited aggregation regime

Two-dimensional diffusion-limited aggregation of spherical microparticles was achieved experimentally as a result of their rectilinear motion (“ballistic aggregation”) at a “water-air” interface. A percolation cluster was obtained and the evolution of its morphological parameters was studied under compression. A change in the orientation of the cluster pores and a nonlinear coalescence and breakup process were observed. A fabrication technology is proposed for monolayer films similar to the Langmuir method. Pis’ma Zh. Tekh. Fiz. 25, 80–85 (December 12, 1999)     

Ethical motivations for green business and engineering

Corporate references to “sustainability” and the operative process of “green business” have become almost commonplace over the past decade. Companies not only seek to comply with environmental regulations, but many have discovered that techniques for reducing adverse environmental impact often have positive effects on corporate profitability as well. Such adoptions of green business and engineering practices are morally neutral because the driving forces behind them are legal and economic, but not ethical. In some instances, however, managers and engineers have undertaken green business initiatives with the notion of doing something positive for future humans and for the natural environment. In this paper we discuss the “green” driving forces behind moral decisions regarding the adoption of green engineering and business practices and conclude that most “green engineering” known to the public is simply good business practice. Only when engineering and business begin the “green engineering” program with the aim of reducing adverse impact on health or environment does “green engineering” become morally admirable.     

Reduced-basis techniques for rapid reliable optimization of systems described by affinely parametrized coercive elliptic partial differential equations

We present a technique for the rapid and reliable optimization of systems characterized by linear-functional outputs of coercive elliptic partial differential equations with affine (input) parameter dependence. The critical ingredients are: reduced-basis approximation to effect significant reduction in state-space dimensionality; a posteriori error bounds to provide rigorous error estimation and control; “offline/online” computational decompositions to permit rapid evaluation of output bounds, output bound gradients, and output bound Hessians in the limit of many queries; and reformulation of the approximate optimization statement to ensure (true) feasibility and control of suboptimality. To illustrate the method we consider the design of a three-dimensional thermal fin: Given volume and power objective-function weights, and root temperature “not-to-exceed” limits, the optimal geometry and heat transfer coefficient can be determined—with guaranteed feasibility—in only 2.3 seconds on a 500 MHz Pentium machine; note the latter includes only the online component of the calculations. Our method permits not only interactive optimal design at conception and manufacturing, but also real-time reliable adaptive optimal design in operation.     

A probabilistic theory of the strength of short-fibre composites with variable fibre length and orientation

This paper adopts a probabilistic approach to examine the effects of fibre length and orientation distribution on the strength of short fibre composites. A general theory has been formulated in terms of fibre length and orientation distribution function as well as the composite geometrical and physical properties. The final result is presented in the form of a modified rule of mixtures. The result has been applied to discuss several special cases of fibre arrangements. They are (a) unidirectional short fibre composites with uniform fibre length, (b) unidirectional short fibre composites with fibre length distribution, (c) random short fibre composites with uniform fibre length and (d) partially-aligned short fibre composites with uniform fibre length. Comparisons of the present results with previous work are also discussed.On leave from the Institute of Space and Aeronautical Science, University of Tokyo, Japan.     

Alignment of silicon carbide whiskers in polymer matrix

Polyacrylonitrile (PAN) loaded with up to 70% by weight of silicon carbide whiskers has been used as a model system to demonstrate the potential of whisker alignment by a technique similar to the conventional fibre spinning. Continuous fibres containing high percentages of whiskers can be readily produced using a laboratory scale conventional wet-spinning apparatus. Excellent whisker alignment along the fibre axes was found even for the as-extruded filaments without drawing. However, an improved alignment was obtained through optimizing whisker loading and by drawing the as-spun fibres. Drawing tends to improve the fibre mechanical properties considerably, rendering them easily handable or even useful as a “composite fibre” reinforcement in their own right. Although whisker alignment generally gets better with drawing, over-stretching leads to irregular fibre diameters. Preliminary experiments show that after some minor modifications, this technique may be applied to fabricate whisker reinforced ceramic composites. This revised version was published online in November 2006 with corrections to the Cover Date.     

The Kramers-Kronig relations for permittivity, “True” screening radius,and critical point of a coulomb system

A correlation between the peculiarities of the electric permittivity (EP) ɛ(q, ω) of a homogenous and isotropic Coulomb system (CS) in the limit of ω → 0, q → 0 and q → 0, ω → 0 is established on the basis of exact limiting relations; general expression for static EP ɛ(q, 0) of a CS is obtained in the region of small wave vectors q. The concepts of a “true” dielectric and “ideal” conductor are introduced. The definition of a “true” screening radius is considered. A critical point of two-component CS is shown to correspond to either the “true” dielectric state or the “ideal” conductor one.     

Studies of the Wetting of Gaps in Weightlessness

The geometry of a thin sheet metal vane terminating near a wall in a surface tension propellant management device (PMD) is common in devices designed by various people. A research program into the capillary fluid physics of the common vane-wall gap began in 1998 with the arrival of the second author at the School of Aeronautics and Astronautics at Purdue University. Drop tower experiments, Surface Evolver computations, and analysis were combined to explore the details of the fluid behavior in the vane-wall gap geometry. Results of four vane-wall gap experiment topics: critical wetting, advance rates, sensitivity to vane orientation, and effect of imperfect initial conditions, are discussed here. This work led to a desire by Weislogel to incorporate this type of geometry into his “Capillary Fluids Experiment” (CFE) that operated flawlessly on the International Space Station in 2006 and 2007. It is found that the wetting of vane-wall gaps is predicted correctly through use of the critical wetting analysis of Concus and Finn. Furthermore, the dynamics of the wetting flows are found to have scaling of flow rates versus time similar to those known for capillary advances in solid corners. In some cases, a seemingly misaligned vane is found to have more rapid capillary advance than for the same vane and gap but with the vane normal to the tank wall. An initial drop tower study of sensitivity to imperfect initial conditions shows that a critical wetting flow is largely immune to small tilts in the initial test orientation but that larger errors can be seen in cases that lack critical wetting and in the measurements of the time history of the meniscus minimum point.