bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Method to Reduce Cure-Induced Stresses in Thermoset Polymer Composites, Part II: Closed Loop Feedback Control System
Authors: Genidy Mohamed S. , Madhukar Madhu S. , Russell John D.
Published: August 2002

A closed loop feedback control system has been developed to obtain cure cycles which reduce the cure-induced stresses in single fiber/matrix model composites. In this feedback system, thermal expansion and stress relaxation are used to counteract the stresses resulting from the chemical shrinkage. The feedback system is applied to two different fibers (carbon and glass) in four different resins [3501-6, 934, and 977-3 epoxies and 5250-4 bismaleimide (BMI)]. The completeness of the cure is verified by comparing glass transition temperature (Tg) for polymers cured using the standard cure cycles (cycles recommended by the prepreg manufactures) and the feedback cure cycles. The durations of the feedback cure cycles are within that of the standard cycles. Test results indicate that feedback cure cycles reduce the curvature of unsymmetrical laminates as a measure of residual stresses.
High Bandwidth Tunability in a Smart Vibration Absorber
Authors: Flatau Alison B. , Dapino Marcelo J. , Calkins Frederick T.
Published: August 2002

An electrically tunable vibration absorber based on the strong δ E effect of Terfenol-D has been developed. A general description of tuned vibration absorbers is presented along with a description of the magnetostrictive effects that make an electrically tunable Terfenol-D vibration aborber function. It is emphasized that the large modulus changes achievable with the proposed magnetostrictive vibration absorber arise as a consequence of the stiffening of the crystal lattice as the magnetic field is increased from the demagnetized state to magnetic saturation. This is in contrast to the small modulus changes often reported in the literature which are achieved by operating smart materials between their open- and short-circuit states. Experimental results are presented that show agreement with prior art and demonstrate control of a magnetostrictive actuator resonant frequency between 1375 Hz and 2010 Hz by electrically varying the elastic modulus of a magnetostrictive material. This operating principle is then implemented to obtain high bandwidth tunability in a Terfenol-D vibration absorber.
Effect of Homogenization as Pretreatment for the Improvement of Autolysis Efficiency of Kluyveromyces fragilis
Authors: Vasallo M. C. , Otero M. A. , García L. , Dopico J. R. , López J. C.
Published: August 2002

A yeast autolysis modified process consisting of a previous homogenization step at 52 MPa ( N= 2) with pH adjustment at 9.5 is developed. The process carried out in 16 h reached a total biomass solubilization around 85%. Autolysis course was not affected by yeast concentration in the studied range (60–140 mg/mL). Initial NaCl concentration of 1% led to a reduced content of this salt in final extract of about 7%, under optimum conditions, in good agreement with current requirements of the food industry. The high levels of biomass solubilization in this process allowed a yield increase of extract from 0.13 kg per liter of yeast suspension (150 mg/mL) in untreated cells to 0.15 kg/L in homogenized cells.
Optimization of Piezoactuator Configuration in Control of Flexible Structures
Authors: Yousefi-Koma A. , Vukovich G.
Published: August 2002

In order to find the optimum dimensions and locations of piezoactuators in the active control systems, a novel procedure for simultaneous dimension and location optimization of piezoactuators for active control of flexible structures is introduced. Three optimization criteria are investigated and compared which leads to an optimal configuration of the actuators particularly relevant when the weight and geometry limitations are important. In the first criterion we seek a configuration of the piezoactuator which maximizes the overall damping ratio of the closed loop system. Minimization of the overall real part of eigenvalues of the controlled system is the second criterion. For the third criterion, we seek the minimum LQR cost function over possible dimensions and locations. The optimization indicates that the best configuration of piezoactuators in active control systems is the shortest and widest.
The Application of Artificial Neural Network (ANN) Technique to Formulation Design of Flame Retardant Polymers. I. Intumescent Flame Retardant PA-66 Composites
Authors: Xia Juntao , Xiao Chongwei , Wang Jianqi , Huang Congming
Published: August 2002

The application of the artificial neural network (ANN) to the formulation design of the halogen-free flame retardant polyamide-66 with natural color was carried out. The ANN based software, flame retardant expert system FRES 2.0 for FR polymer formulation design, was developed and used in this study. The optimized output gives LOI values in accordance with experiments. It follows that the three-layer BP (back-propagation) network based modeling proved to be most useful in dealing with problems with serious non-linearity encountered in formulation design of flame retardant polymer compounds.
Studies on Effect of Water Repellent Treatment on Flame Retardant Properties of Fabric
Authors: Shekar R. Indu , Kasturiya N. , Raj H. , Mathur G. N.
Published: August 2002

Inherently flame retardant fibre blended with dope treated flame retardant fibre (KR/VR), fabric and dope treated flame retardant fibre (TR) were treated with fluorocarbon emulsion at different concentrations, curing temperature so as to investigate the effect of above parameters on repellency properties and their implication on flame retardant properties. The repellency properties were evaluated by contact angle, spray rating and oil repellency, whereas, flame retardant properties were evaluated by limiting oxygen index and char length. Thermal studies (TGA) were also carried out so as to study the possible changes in thermal chemistry of the fabrics. The fabrics were finally evaluated on Kawabata system for the objective evaluation of hand properties in terms of low stress mechanical properties and thermal insulation. The thermogravimetric studies elucidate that there is no change in the thermal chemistry of the fabric treated with fluorocarbon emulsions.

The blended fabric (KR/VR) exhibited overall satisfactory performance (both functional and hand properties) compared to TR fabric.
Pulse-Modulated RF Thermal Plasma for Advanced Materials Processing
Authors: Ishigaki Takamasa , Sakuta Tadahiro
Published: August 2002

Thermal plasma has been used for various kinds of materials processing. For further extension of the variable process parameters and the applications of thermal plasma, a time-domain controlled generation was developed of the pulse-modulated RF induction plasma, which has been successfully generated by the present authors, for the first time, with a sufficiently high electric power for the advanced materials processing. At the first stage, the steep overshoot and undershoot of the coil current amplitude of oscillating frequency of 1 MHz were recognized at the time instances of pulse on and off, giving a limited range of stable generation. Two solutions were found for suppressing the magnitude of overshoot and undershoot. One is the introduction of shimmer level, which is a ratio of coil current magnitude between pulse-on and -off periods. The other is that the rise and decay times of RF current was made a little slow in time domain. Consequently, when the Ar-H2 plasma was generated under 750 Torr with a high power level of 17 kW, the low power level went down to about 4 kW, i.e. below 1/4 of the higher level, with which such low power level, the continuous plasma generation was unable to be sustained. The increased difference between the high and lower power levels was large enough to give rise to the non-equilibrium condition in plasma temperature and composition at the instances of pulse on and off. Such unique condition is expected to offer a unique physico-chemical condition for advanced materials processing. The range of well-controlled generation of the pulse-modulated plasma was determined for Ar-H2 plasma with various parameters. It was recognized that the duration of pulse-on and -off times as well as the shimmer current level are the important parameters, which determine the degree of deviation from equilibrated condition in high pressure thermal plasma.
Management of Pulmonary Disease in Patients with Cystic Fibrosis
Authors: Robinson Christine A. , Kuhn Robert J.
Published: August 2002

Cystic fibrosis is the most common, life-shortening autosomal recessive disease, affecting approximately 1 in 3400 live births in the United States. Gastrointestinal and pulmonary manifestations are most common. With the introduction of pancreatic enzyme and vitamin supplementation, lung disease accounts for the vast majority of morbidity and mortality in patients with cystic fibrosis. The lungs of cystic fibrosis patients are essentially normal at birth but demonstrate evidence of airway inflammation and infection in early infancy. A vicious cycle of inflammation, infection and obstruction ultimately leads to destruction of airways, impairment of gas exchange and death.

Current pharmacological management of pulmonary disease targets reducing airway obstruction, controlling infection and more recently, controlling inflammation. An increased recovery of unusual and highly resistant bacteria from patients with more advanced disease has been observed. Aggressive treatment of acute pulmonary exacerbations with combination antibiotic therapy for two to three weeks has shown pronounced beneficial effects. The routine use of prophylactic antistaphylococcal antibiotics is still controversial.

Although current pharmacologic treatment is symptomatic, new agents are being developed and studied that target the underlying defect in the CFTR protein. This review focuses on current pharmacologic management of pulmonary disease in patients with cystic fibrosis and the role of new agents emerging for the treatment of this disease.
Heating of Magnetorheological Fluid Dampers
Authors: Gordaninejad Faramarz , Breese Darrell G.
Published: August 2002

This paper presents experimental and theoretical studies on heat generation and dissipation of fieldcontrollable, magneto-rheological (MR) fluid shock absorbers. Since MR fluid dampers are energy-dissipating devices, the issues of heat generation and dissipation are important. In this study, experiments are conducted on a variety of MR fluid dampers that have been designed, developed, and tested at the University of Nevada, Reno (UNR), for specific applications. Each MR fluid damper is experimentally evaluated for temperature changes that result from various types of sinusoidal input motions. In addition a theoretical model is developed which predicts the temperature increase of the MR fluid dampers. This model is solved numerically, and is compared with experimental results. Also, a non-dimensional form of the governing equations is developed to assess the effect of physical parameters on the heat dissipation as well as heat generation within the MR fluid damper. Moreover, the theoretical results for temperature rise of a MR fluid damper under a seismic force are presented. In all cases, the temperature effect on the damping force is significant.
Simulations and Experiments on Low-Pressure Permeation of Fabrics: Part I—3D Modeling of Unbalanced Fabric
Authors: Dungan F. D. , Senoguz M. T. , Sastry A. M. , Faillaci D. A.
Published: August 2002

Conformation of fabrics to complex molds during composite processing induces significant fabric deformation and local shear, which in turn alter the processability of these preforms from their unsheared, flat configuration. The present work (Parts I and II) establishes that although composite mold processing can often be described generally by a percolation flow assumption (e.g., Darcy or Poiseuille flow), changes in microarchitecture of fabric in shear result in markedly different flow fronts. We reiterate our earlier finding that use of a transformed Darcy law (i.e., mathematical transformation of tensor of undeformed permeability, to the sheared configuration) does not accurately predict permeability for sheared fabrics. In essence, the effect of the change in microarchitecture of the fabric is not captured by mathematical transformation of the tensorial permeability. Wealso point out the deficiencies of semi-empirical approaches in determining sheared fabric permeability. We then develop a 3D fabric model, which is used to quantify the effects of nesting and changes in gap architecture with shear angle. We show that nesting produces gaps in molds in commonly-used permeability experiments which easily exceed single-layer fabric thicknesses when more than a few layers are used, but that this condition is easily detectable in an experiment (i.e., Poiseuille flow between topmost layer and mold top is easily detected). We also show that shear angle (in our case,. = 0°, 15°, and 30°) produces little difference in nesting, though it significantly alters fabric microstructure and the sizes and shapes of intralayer gaps. In Part II of this paper, we use this fabric model to predict fabric permeability. Our work suggests that departure from the more traditional approach of generation of a large suite of data from permeation experiments to determine manufacturability of preforms, in favor of computational simulation of fabric geometries, is well-justified.
Neural Network Discrimination in Intelligent Vibration Control
Authors: Song J. -K. , Washington G.
Published: August 2002

The overall goal of this study lies in the multi-mode structural vibration control for systems, based on spatial information. In order to accomplish this task, a neural network was designed to identify the shape of the dominant vibration mode by using properly located piezoelectric sensors. The network then chose a set of scaling gains for a fuzzy logic controller that had been optimally tuned for that particular mode’s shape. Next, a fuzzy logic controller was employed to control the vibratory system. The novel technique was experimentally verified on an aluminum cantilever beam system that was augmented with two lead zirconate titanate (PZT) actuators and two PZT sensors. The optimized control strategy was then compared to traditional fuzzy logic control. Finally the mass of the plant was increased by over a factor of 1.5 and the same controller was used to adequately stop vibration.
On Raleigh Equation and Accuracy of its Real Roots Calculations
Authors: Nesvijski Edouard G.
Published: August 2002

Composite materials require adequate means of nondestructive testing, evaluation, and monitoring. Ultrasonic methods and tools are one means to meet these objectives. The latest advances of electrical and electronic engineering and nondestructive testing methods provide the foundation for a wide class of modern ultrasonic equipment. However, some recent experimental results require reevaluation of existing basic theories, especially in the field of acoustic wave propagation. More accurate calculations of the real roots of the Rayleigh equation with their value approximations by different polynomials given in this paper may be useful for improvement of nondestructive testing of materials. This work also considers additional roots of the Rayleigh equation as a basis for new types of surface waves.
Viscous Synergism in Carrageenans (κ and λ) and Locust Bean Gum Mixtures: Influence of Adding Sodium Carboxymethylcellulose
Authors: Hernández M. J. , Dolz J. , Dolz M. , Delegido J. , Pellicer J.
Published: August 2002

Synergistic interactions between locust bean gum (LBG) and two types of carrageenans (κ and λ) are studied. Viscous synergism index, Iv as a function of concentration ratio z=ćLBG/ćcar, and shear rate were obtained for every mixture. In both binary systems the values of this index decrease with increasing shear rate. For the LBG + κ mixtures, Ivpresented a maximum at a concentration ratio z≅60/40, which would be considered the optimum proportion of gums in the mixture. However, for the LBG + λ system, I vincreased with z in the whole interval considered, i.e., the highest synergism corresponded to the lowest proportion of carrageenan. The addition of sodium carboxymethylcellulose (NaCMC) to the binary systems modified the above results. For LBG + κ + NaCMC mixtures, the maximum Ivvalues were similar to those corresponding to LBG + κ system, but the concentration ratio at which these maxima are produced shifted to a lesser proportion of locust bean gum ( z ≅40/60). Moreover, the presence of NaCMC in the other ternary system totally eliminated the possible interaction between LBG and λ-carrageenan.
Sensing of Delaminations in Composite Laminates using Embedded Magnetostrictive Particle Layers
Authors: Krishnamurthy A. V. , Anjanappa M. , Wang Z. , Chen X.
Published: August 2002

This is an exploratory study to illustrate the feasibility of detecting delamination type of damage in polymeric laminates with one layer of magnetostrictive particles. One such beam encircled with excitation and sensing coils is used for this study. The change in stress gradient of the magnetostrictive layer in the vicinity of delamination shows up as a change in induced voltage in the sensing coil, and therefore provides a means to sense the presence of delamination. Recognizing the constitutive behavior of the Terfenol-D material is highly nonlinear, analytical expressions for the constitutive relations are developed by using curve fitting techniques to the experimental data. Analytical expressions that relate the applied excitation field with the stress and magnetic flux densities induced in the magnetostrictive layer are developed. Numerical methods are used to find the relative change in the induced voltage in the sensing coil due to the presence of delamination. A typical example of unidirectional laminate, with embedded delaminations, is used for the simulation purposes. This exploratory study illustrates that the open-circuit voltage induced in the sensing coil changes significantly (as large of 68 millivolts) with the occurrence of delamination. This feature can be exploited for device off-line inspection techniques and/or linking monitoring procedures for practical applications.
Finite Element Analysis of Temperature Induced Stresses and Deformations of Polymer Composite Components
Authors: Wang J. , Kelly D. , Hillier W.
Published: August 2002

Due to the heterogeneous nature of composite materials, residual stresses build up during manufacture of composite products. Such stresses can change the final shape of a component from the tool shape. Temperature induced stresses and deformations of thick cylindrical parts have been studied by a number of researchers using analytical approaches. However these approaches cannot solve a thick composite component with arbitrary geometry. Finite-element-method (FEM) analysis was conducted in this study using ABAQUS. Mechanical and thermal properties of composite materials were determined through microstructure analysis. Different element types were compared with respect to their prediction accuracy. The technique of application of FEM is discussed in the paper. Spring-in values of 90° angles with varying curvature at the corner are predicted. Reasonably good agreement between the prediction and the measurement is achieved.
Uniaxial and Biaxial Tensile Strength of Calf Pericardium Used in the Construction of Bioprostheses: Biomaterial Selection Criteria
Authors: García Páez José M. , Carrera Antonio , Cordón Angeles , Jorge-Herrero Eduardo , Rocha Aurora , Salvador Josét , Méndez Jesús , Castillo-Olivares José L. , Milláan Isabel , Sainz Natividad
Published: August 2002

Using morphological and mechanical criteria and applying a method involving paired samples that is widely employed in epidemiology, we obtained an excellent prediction of the mechanical behavior of the calf pericardium used in the construction of cardiac bioprostheses. The method of selection employed in this study may be a highly useful tool for guaranteeing the mechanical resistance of calf pericardium, with a very low level of error.
Stacking Sequence Design of Fiber-Metal Laminate for Maximum Strength
Authors: Nam H. W. , Hwang W. , Han K. S.
Published: August 2002

FML (Fiber-Metal Laminate) is a new material combining thinmetal laminate with adhesive fiber prepreg. It has nearly all the advantages of metallic and composite materials, including good plasticity, impact resistance, processibility, light weight and excellent fatigue properties. However, in most FML the fiber prepreg is staked in only one direction, although FML can be designed with a varying stacking sequence angle of fiber prepreg. No work has been published on the optimum design of FML. This paper uses genetic algorithms to study the optimal design of FML under various loading conditions. To analyze FML the finite element method is used based on shear deformation theory. The Tsai-Hill failure criterion and theMiser yield criterion are used as the objective functions of the fiber prepreg and the metal laminate, and the ply orientation angles are the design variables. In the genetic algorithm, tournament selection and the uniform crossovermethod are employed. The elitist model is also used for an effective evolution strategy, and the creeping random search method is adopted so as to approach the solutionwith high accuracy. Optimization results are given for various loading conditions and are compared with CFRP (Carbon Fiber Reinforced Plastic). The results show that FML is better than CFRP in most loading conditions. In particular, FML shows good mechanical performance in point and uniform loading conditions and is more stable to unexpected loading.
Factors in the Compressive Strength of Composite Sandwich Panels with Thin Facesheets
Authors: Lagace Paul A. , Mamorini Luca
Published: August 2002

An experimental investigation was conducted to investigate the contribution of various factors to the compressive strength of composite sandwich panels with thin facesheets. The main factors investigated were the laminate configuration and the inclusion of notches, the latter to provide information on the damage tolerance of such configurations. Tests were conducted on sandwich panels with 25.4 mm thick Nomex honeycomb core and secondarily-bonded facesheets made from AWl 93PW/3501-6 graphite/epoxy fabric. Two different facesheet configurations, both 0.35 mm thick and consisting of two plies of the fabric, were investigated: (0/90) and (45). Unnotched specimens and specimens with holes ranging from 3.18 mm to 9.53 mm in diameter were tested monotonically to failure in compression. In a number of applications of thin graphite/epoxy facesheets in sandwich configurations, it has been reported that the existence of facesheet wrinkling played a significant role in the response and failure of these panels. This includes a reduction in the failure load from that anticipated. The possibility of the existence of face wrinkling and the factors involved were investigated by placing strain gages on both facesheets in a number of locations. This included strain gages within the region of influence of the hole for these specimens. Specimen failure was seen to be a result of compressive failure of the facesheets. Evidence of any local instability of the facesheets possibly indicative of wrinkling was observed in the strain response for only one particular configuration. However, the failure mechanisms did not indicate any instability in all cases. The failure mechanism was dependent on the facesheet configuration as was response to the presence of notches. The (0/90) facesheet configuration showed an almost linear stress-strain curve up to failure. Failure occurred with a neat fracture perpendicular to the applied load. This case showed typical sensitivity to the presence of the notches for hole diameters larger than 3.18 mm and was adequately correlated using available models for composite laminates. For the (45) facesheet configuration, a highly stress-strain behavior was observed much as in tension tests. Damage patterns at failure were characterized by fractures developing along the +45 and -45O directions and at the interply
Crystallization and Morphology of Propylene/Pentene Random Copolymers
Authors: Juhász P. , Belina K.
Published: August 2002

Crystallization and melting behavior of propylene/1-pentene random copolymers were studied. WAXD and d.s.c. measurements of isothermal crystallized samples confirm that the copolymers contain the γcrystal form in large quantity. The content of γform increases with increasing pentene content and crystallization temperature. We found a limitation in the relative γcontent around 60–65%. The efficiency of pentene comonomer is much higher than of ethylene. The equilibrium melting point decreases with pentene content in a nonlinear fashion, and the values are much lower than the theoretical ones.
Vibration Control of a MR Seat Damper for Commercial Vehicles
Authors: Choi Seung-Bok , Nam Moo-Ho , Lee Byung-Kyu
Published: August 2002

This paper presents vibration control of a semi-active seat suspension with a magneto-rheological (MR) fluid damper, which is applicable to commercial vehicles such as large size of trucks. A cylindrical MR seat damper is designed on the basis of the Bingham model of the MR fluid. After manufacturing the seat damper, field-dependent damping force characteristics are experimentally evaluated. A semi-active seat suspension system installed with the seat damper is then constructed and its governing equation of motion is derived. A skyhook controller to reduce vibration level at the driver’s seat is formulated and realized in a closed-loop control fashion. The control responses, such as acceleration transmissibility, are investigated in both frequency and time domains. In addition, a full-vehicle model featuring the proposed semi-active seat suspension is established and its vibration control performances are evaluated via the hardware-in-the-loop simulation (HILS).
Spray Foam Beyond HCFC-141b
Authors: Feighan J. , Stewart R. , Singh S. , Abisaleh T.
Published: August 2002

Sprayed rigid foam is a significant segment of the polyurethane industry, and as in other rigid foam segments, spray foam formulators need to find ways to meet current product requirements when the use of HCFC-141b is phased out in January 2003. Due to some of the unique characteristics of the spray foam industry, though, the choice of a replacement blowing agent is perhaps more complex than in any other rigid foam sector. The alternatives receiving the most consideration today are HFC-245fa, hydrocarbons, and water.

All of these potential blowing agents have significant hurdles to overcome before they could serve as satisfactory replacements for HCFC-141b in the spray foam market. As of May 1999, a firm commitment to commercialize HFC-245fa has not been made. The use of hydrocarbons in spray would require significant improvements in safe handling procedures and modifications to spray equipment due to flammability issues. And with water-blown systems, dimensional stability and adhesion are two technical hurdles that must be overcome. It is conceded as well that insulation performance (as measured by initial k-factor) will not be as good for a water-blown foam as with HCFC-141b.

It was because of the lack of an obvious HCFC-141b replacement for the spray foam industry that Huntsman Polyurethanes decided to investigate possible solutions. Any alternative would need to meet the processing and handling requirements that are currently met with HCFC-141b systems.

The objective of this work is to develop zero-ODP (ozone depletion potential) technology that meets the performance characteristics that are currently achieved with HCFC-141b spray foam roofing systems. The focus of this paper is on the development of water-blown technology for roofing systems. Foams were processed via high-pressure spray equipment in a controlled environment. The study looked at the effect of polyol, catalyst, blowing agent, and processing variables on foam quality.
Predicting the Axisymmetric Manufacturing Deformations of Disk-Style Benders
Authors: Hyer Michael W. , Jilani Adel B.
Published: August 2002

The thermally-induced deformations of multilayer disk-style benders that are consolidated at elevated temperature to cure the adhesives bonding the layers together and then cooled to room temperature are studied. Only axisymmetric deformations are considered, and hence the disks cool to a dome-like shape due to the different thermal expansion properties of the layers. The paper derives the equations governing the deformation and, since the out-of-plane deformations are often many times the disk thickness, geometrically nonlinear effects are considered in the derivation. As a comparison case, the equations are linearized and solved in closed form. The geometrically nonlinear case is solved by using the shooting method and the Rayleigh-Ritz method. A number of simple bender designs are studied to examine the influence of geometric nonlinearities, disk geometry, and layer material properties on the deformations. It is concluded that geometric nonlinearities lead to flattening of the dome relative to the geometrically linear case, and the thermally-induced deformations are sensitive to layer material properties, layer thickness, and disk radius.
Stress Relaxation Profiles of Molded and Extruded Thermoplastics Using Dynamic Mechanical Analysis
Authors: Lee-Sullivan Pearl , Dykeman Donna
Published: August 2002

The stress relaxation profiles across the skin-core-skin layers of injection molded polycarbonate and extruded polyethylene sheet are presented. The profiles were obtained by progressively removing the layers followed by stress relaxation tests using a Dynamic Mechanical Analyzer (DMA). The machined layers were characterized using the elastic modulus, Eo, and the relaxation time, o. It was found that the DMA was able to distinguish the differences in viscoelastic response across the thickness of the polymer samples. The variation in behaviour was consistent with the expected morphology and molecular orientation developed due to the processing method.
Building Engineering— A Needed Discipline
Authors: Hens Hugo , Vermeir Gerrit , Carmeliet Jan , Janssens Arnold
Published: August 2002

Building design and building construction are in permanent evolution. Program complexity increases. Building technology does not stop changing from “an art” to an engineering and science-based field of knowledge and application. Fitness for purpose, backed by user, corporation and society demands, and translated into performance requirements more and more define and help in assuring quality. Hence, these evolutions should direct the construction sector toward an integrated approach.They, however, are counteracted by the split between design, consultancy and construction, the fragmentation of the sector, its guild's mentality, the manufacturing side denying responsibility, the low level ofR& Dinvestments and the absence of a quality tradition. The traditional education in architecture hardly considers these evolutions and does not try to impact the drawbacks. On the contrary, its focus is on producing designers who create buildings as most original pieces of art. This, of course, is not unimportant, but it demands a parallel education that may be called building engineering.
Ultrastructure of Exogenous Surfactants Using Cryogenic Scanning Electron Microscopy
Authors: Banerjee R. , Bellare Jayesh R.
Published: August 2002

Therapy with specialised biomaterials, exogenous surfactants, is known to significantly decrease the mortality rates in Respiratory Distress Syndrome (RDS). Surfactants available commercially vary widely in composition and biophysical properties. The present paper studies the ultrastructure of three exogenous surfactants used for the treatment of Respiratory Distress Syndrome, namely, Survanta™, ALEC™ and Exosurf Neonatal™ with respect to their ability to form liposomes using cryogenic scanning electron microscopy. Liposomal organisation is more obvious in Exosurf than in Survanta and is most pronounced in ALEC. ALEC forms closed regular liposomes with an onion-ring-like internal bilayer arrangement. Survanta forms open membranous structures with wavy ribbon-like membranes. The complex membrane-like structures seen with Survanta may be due to the interaction of lipids with surfactant-specific proteins present in this surfactant which is derived from natural lung extracts and might indicate superior spreading at the lipid-water interface. Artificial protein-free surfactants (ALEC and Exosurf) did not appear to form these open membranous structures. Further study of the ultrastructure of possible biomaterials as surfactants could help in the development of new, improved artificial protein-free surfactants with open membranous structures that might facilitate spreading at the air-liquid interface of lungs.
Quantitative Radiographic Analysis of Fiber Reinforced Polymer Composites
Authors: Baidya Krishna P. , Ramakrishna S. , Rahman M. , Ritchie A.
Published: August 2002

X-ray radiographic examination of the bone fracture healing process is a widely used method in the treatment and management of patients. Medical devices made of metallic alloys reportedly produce considerable artifacts that make the interpretation of radiographs difficult. Fiber reinforced polymer composite materials have been proposed to replace metallic alloys in certain medical devices because of their radiolucency, light weight, and tailorable mechanical properties. The primary objective of this paper is to provide a comparable radiographic analysis of different fiber reinforced polymer composites that are considered suitable for biomedical applications. Composite materials investigated consist of glass, aramid (Kevlar-29), and carbon reinforcement fibers, and epoxy and polyether-ether-ketone (PEEK) matrices. The total mass attenuation coefficient of each material was measured using clinical X-rays (50 kev). The carbon fiber reinforced composites were found to be more radiolucent than the glass and kevlar fiber reinforced composites.
Effect of Bonding on the Performance of Segmented Piezoceramic Actuators
Authors: Ilegbusi Olusegun J. , Ballas Matthew W.
Published: August 2002

The deflection of various single-joint segmented piezoelectric actuators under the influence of an applied electric field is simulated in 2D. Two geometries are considered, both based on a simple cantilever beam configuration: Case 1 involves joining the individual actuators end-to-end while in Case 2, they are joined face-to-face. The effect of various ceramic-to-joint modulus ratios (y) on the maximum and tip displacements is investigated. In Case 1, it was determined that yplays a significant role in the overall curvature of the actuator but has very little effect on the tip displacement. Case 2 showed that a loweryresults in a larger average tip displacement while y? 5 causes severe distortions at the free end of the actuator.
Dissolution of Atmospheric Gases in Polystyrene Melt in Single and Twin-Screw Foaming Extruders
Authors: Zhang Q. , Xanthos M. , Dey S. K.
Published: August 2002

Dissolution and solubility characteristics of carbon dioxide in polystyrene melt were studied in both single screw and twin-screw foaming extruders. The effects of the main processing conditions on the gas dissolution behavior were also studied. Solubility data obtained from the twin-screw extrusion experiments showed better consistency compared with those obtained from the single screw experiments, indicating the importance of enhanced mixing in affecting the gas dissolution and solubility behavior during an extrusion foaming process. Gas dissolution inside a single screw foaming extruder was studied for three atmospheric gases (carbon dioxide, nitrogen and argon) in polystyrene melts. The results were compared with those obtained in a twin-screw extruder for the carbon dioxide-polystyrene system in an effort to elucidate mechanisms for the complex process of gas dissolution inside a foaming extruder.
Fatigue Issues of Polymeric Foam Sandwich Core Materials in Simple Shear
Authors: Kiepert K. T. , Miskioglu I. , Sikarskie D. L.
Published: August 2002

Obtaining the fatigue properties of sandwich core materials is a particularly difficult issue. This work evaluates the ASTM C 394 test procedure for determining the fatigue properties of core materials using compression-compression loading. The stress concentration at the ends of the specimen where the specimen meets the fixture has been suggested to lead to premature failures. A geometric optimization of specimen ends was attempted to minimize the effects of the stress concentration. This resulted in removing a circular arc of material from the specimen ends. While this allowed the stress concentration to be shifted away from the corner interface of the specimen and fixture, it did not seem to positively influence the fatigue life for the load levels tested. Fatigue results obtained using the compression-compression loading compared well with data obtained using other test methods, including four-point bending. This suggested that the current ASTM C 394 test standard, when used with compression-compression loading, allows acceptable fatigue data to be obtained for foam core materials.
Experimental Study on Characteristics at Early Stage of Fire—Measurement and Analysis on Early Development of Flame Image Area
Authors: Lizhong Yang , Zhihua Deng , Weicheng Fan , Qing’An Wang
Published: August 2002

Generally speaking, some characteristics describing the early stage of fire include: heat release, smoke release, flame spread, toxic effluents, melting and dripping. To study these characteristics, an experimental setup must first be established. This paper presents results of experiments and mainly discusses the increase in flame image area of a fire during its early stage. The analysis shows that the flame image area of a fire at an early stage increases continuously, and the increase rule can be described using a geometrical function.
Innovative Fatigue Method in Single-Lapped Mixed Composite Joints
Authors: Lin Wei-Hwang , Jen Ming-Hwa R.
Published: August 2002

The aim of the work is to systematically investigate the mechanical properties of single-lapped mixed, i.e., bolted and bonded and riveted and bonded, composite joints subjected to tension-tension (T-T) cyclic loading by using the new model grips in comparison with that by conventional MTS grips. A system of devices to measure clamping force is disclosed. The U.S. patent new model grips are introduced and manufactured to conduct cyclic tests and generate empirical results, highlighted as follows. Through the parametric study we find that the obtained fatigue strength and life of the mixed joint by MTS grips are larger than that by new model grips, i.e., the real values are over-estimated by MTS grips. Our data by new model grips are correct. The bolted and bonded joint is found stronger than the riveted and bonded joint mainly attributed to the features of respective mechanical fastening. The mixed joint of cross-ply adherend is more resistant to cyclic loading than that of quasi-isotropic adherend. Additionally, the overlap length and clamping force are two dominant factors in fatigue strength and life. The increase in overlap length of a mixed joint will increase the fatigue strength and life until an asymptotical value is approached. Similarly, the increase of clamping force will result in a rigid joint to possess more resistance to cyclic loading.
Vibration Welding of Continuously Reinforced Thermoplastic Composites
Authors: Bates Phil , Couzens Don , Kendall Jillian
Published: August 2002

Continuous fiber reinforced composites are used in a variety of aerospace, automotive and industrial applications. The ability of thermoplastic composites to be melted and subsequently resolidified allows joining processes such as vibration welding to be used. In this research, vibration welding was used to join polypropylene plates reinforced with woven glass fibers. The effect welding parameters, such as meltdown, weld pressure and weld geometry were investigated. Vibration welding is shown to join highly reinforced composite materials with weld strengths approaching those of short fiber composites.
Design Analysis and Experimental Evaluation of an MR Fluid Clutch
Authors: Lee Usob , Kim Dohyun , Hur Nahmkeon , Jeon Doyoung
Published: August 2002

An MRC (Magneto-Rheological Clutch), a device to transmit torque by shear stress of MR fluids, has the property that its power transmissibility changes quickly in response to control signal. In this study, we consider methods to predict performance of an MRC. First, we anticipate the performance of an MRC with a simplified mathematical model and second, we predict the performance in consideration of the applied magnetic field and viscosity distribution of fluids caused by the field. Between the two methods, compared with experimental results, it is shown that the numerical method is closer to reality than the simplified one.
Effect of the Molding Conditions on Mode II Interlaminar Crack Propagation in Continuous Glass Fiber/Polypropylene Composites
Authors: Bureau M. N. , Denault J. , Dickson J. I.
Published: August 2002

The effect of molding conditions on the resistance to Mode II interlaminar crack propagation under monotonic and cyclic loading of unidirectional continuous glass-fiber composites with a polypropylene (PP) matrix was studied. The distribution of the fibers and of the crystalline and amorphous components of the matrix phase, the melting temperature and the amount of crystallinity are related to the molding conditions employed and to the resulting flexural strength and modulus, apparent interlaminar shear strength and Young’s modulus. Mode II crack propagation, either cyclic or monotonic, is strongly affected by the fiber-matrix interface and matrix morphology. The distribution of the soft amorphous PP phase in the semi-crystalline PP matrix appears to be the controlling parameter determining the fracture and fatigue resistance of the composite. The fractographic features clearly show the role that this phase plays during crack propagation. A relationship between the shear cusp size measured on the fatigue surfaces and the cyclic strain energy release rate is proposed.
Evaluation of the Burning Characteristics of Vegetable Oils in Comparison with Fuel and Lubricating Oils
Authors: Koseki Hiroshi , Natsume Yasutada , Iwata Yusaku
Published: August 2002

Burning characteristics of vegetable oils, lubricating oils and fuel oils were obtained by experiments using 90 mm diameter stainless steel pans. In comparison with these burning characteristics, it was found that the flame height and flame radiation and burning rate of vegetable oils were larger than those that were expected from their flash points. Consequently, it was found that once a fire occurs, the danger of its propagation was similar to that of some lubricating oils and C-fuel oil.
Impedance-Based Structural Health Monitoring with Artificial Neural Networks
Authors: Lopes Vicente , Park Gyuhae , Cudney Harley H. , Inman Daniel J.
Published: August 2002

This paper presents a non-model based technique to detect, locate, and characterize structural damage by combining the impedance-based structural health monitoring technique with an artificial neural network. The impedance-based structural health monitoring technique, which utilizes the electromechanical coupling property of piezoelectric materials, has shown engineering feasibility in a variety of practical field applications. Relying on high frequency structural excitations (typically >30 kHz), this technique is very sensitive to minor structural changes in the near field of the piezoelectric sensors. In order to quantitatively assess the state of structures, multiple sets of artificial neural networks, which utilize measured electrical impedance signals for input patterns, were developed. By employing high frequency ranges and by incorporating neural network features, this technique is able to detect the damage in its early stage and to estimate the nature of damage without prior knowledge of the model of structures. The paper concludes with experimental examples, investigations on a massive quarter scale model of a steel bridge section and a space truss structure, in order to verify the performance of this proposed methodology.
Studies on Composites Based on Acrylonitrile Butadiene Rubber and High Styrene Resin
Authors: Nayak N. C. , Tripathy D. K.
Published: August 2002

Blends of acrylonitrile butadiene rubber, NBR (-CN content 33%) and emulsion polymerized high styrene resin (styrene content 65%) abbreviated as HSR are being investigated for their physico-mechanical, oil resistant, antistatic properties. It is observed that hardness, modulus, tear strength, compression set, tension set, increases with increasing content of HSR. But tensile strength, elongation at break, abrasion loss, oil resistance, cycles to crack initiation, failure and propagation decreases with increasing content of HSR. Even though volume resistivity decreases with increasing content of HSR, the values are within antistatic range. Volume resistivity does not change appreciably even after aging and flexing.
Piezoelectric Hydraulic Pump Development
Authors: Mauck Lisa D. , Lynch Christopher S.
Published: August 2002

A piezohydraulic pump is presented that makes use of the step-and-repeat capability of piezoelectric actuators. This work discusses piezohydraulic pumping theory, pump design, and pump performance. Efficiency is analyzed for the pump cycle with theoretical efficiency being 1.0. Loss mechanisms that result in actuator heating are discussed. The pump was constructed and connected to a hydraulic actuator. The actuator was driven at 7 cm/sec with a 271 N (61 lb) blocking force. To achieve this, the piezoelectric stack actuator was driven at 60 Hz.
Review of Smart-Materials Actuation Solutions for Aeroelastic and Vibration Control
Authors: Giurgiutiu Victor
Published: August 2002

The paper reviews recent achievements in the application of smart-materials actuation to counteract aeroelastic and vibration effects in helicopters and fixed wing aircraft. A brief review of the induced-strain actuation principles and capabilities is done first. Attention is then focused on the smart rotor blade applications. Induced twist, active blade tip, and active blade flap are presented, with emphasis on experimental results. The fixed wing aircraft applications are considered next. Experiments of active flutter control, buffet suppression, gust load alleviation, and sonic fatigue reduction are discussed. Conclusions and directions for further work are presented at the end of the paper.
An Adaptive Herschel-Quincke Tube
Authors: Griffin Steve , Huybrechts Steve , Lane Steven A.
Published: August 2002

Acoustic side branches and mufflers are commonly used to attenuate harmonic disturbances in ducts. This work introduces a variation to the classic Herschel-Quincke tube side-branch configuration to adaptively attenuate the propagation of plane wave disturbances along a duct. Through the use of an active membrane or piston element within the tube, the transmission loss characteristics of the tube apparatus can be made to adapt to changes in the disturbance frequency. This permits tracking of tonal disturbances over a wide bandwidth in order to maintain optimal attenuation. The theory for an adaptive Herschel-Quincke tube is presented, and the corresponding transmission loss is derived and given in terms of the tube geometry, piston mass, stiffness and damping. As an illustrative example, analytical results are presented using a PVDF membrane as an equivalent piston. The derivation of the equivalent piston mass and stiffness of the membrane as a function of applied voltage is also presented. Analytical results illustrate how the transmission loss of the adaptive Herschel-Quincke tube can be varied as a function of the voltage applied to the membrane in order to track changes in the disturbance.