bluuebunny/crossref_metadata_2025 huggingface dataset:
Conservative Treatment of Acute Knee Ligament Injuries—Long-Term Results
Authors: Järvinen M , Kannus P
Published: March 2009

A total of 221 patients were treated conservatively for acute knee ligament injuries at the Tampere University Central Hospital in Finland between 1975 and 1981. Ninety-eight patients had an acute tear of the anterior cruciate ligament (ACL), alone (37) or in combination with the medial collateral ligament (MCL) (61). Ninety-six had an isolated MCL injury, and 27 had an isolated injury of the lateral ligament compartment (LAT) of the knee.

The patients were immobilized in plaster cast, posterior splint, or knee bandage, and no attempts were made to correct ligamentous instability. The patients started isometric exercises of the quadriceps and hamstrings during the first one to two weeks of the immobilization period. Straight leg raises were usually instituted within the first two to four weeks. Walking with crutches with partial weight-bearing was allowed approximately one to two weeks after injury, and full weight-bearing was allowed after two to five weeks. Increasing mobilization and rehabilitation of the injured knee was usually begun immediately after the immobilization period, and the rehabilitation continued under supervision of the attending surgeon for at least six months.

The follow-up study of the patients (average, eight years after the injury; range four to twelve years) included a questionnaire; clinical examination; functional tests; radiological examination; knee strength measurements by a isokinetic testing device; the Lysholm and Marshall scales for subjective, clinical, and functional evaluations; and the authors' scales for radiological and muscle strength evaluations.

The multidimensional follow-up analysis revealed that the long-term outcome after a Grade II sprain (partial tear) of the ACL, MCL, or LAT was good and acceptable even if residual mild or moderate laxity was often demonstrable. In Grade III sprains (complete tears), the long-term results were poor, involving an unstable knee with thigh muscle weakness, post-traumatic osteoarthritis, and severe subjective symptoms.
Alpine Injury Pattern at Waterville Valley—1989 Update
Authors: Young LR , Lee SM
Published: March 2009

The 1988/1989 Waterville Valley, NH, injury patterns show a further decline in lower leg injuries and a trend toward a reduction in knee and thumb injuries. Advanced skiers are now far more likely to injure the upper body, especially shoulder, thumb, or head, than the lower body. The introduction of a high-speed quadruple lift at Waterville Valley in 1988/1989 was associated with only a modest increase in injury rate.
Alpine Skiing Injuries in Scandinavian Skiers
Authors: Ekeland A , Holtmoen Å , Lystad H
Published: March 2009

The skiing injuries and skiing behavior of skiers from Norway, Sweden, and Denmark were studied in 4 Norwegian ski resorts during the winter of 1985/1986. A total of 328 injured skiers were recorded and compared with a randomly selected control population of 316 uninjured skiers.

The skiing injury ratio—injured skiers (%)/uninjured skiers (%)—was significantly higher for Danes (2.0) than for Norwegians (0.9) and Swedes (1.0) (P < 0.01). This national difference was also observed after correction for skiing ability and skiing experience, which are the main determinants of injury risk in alpine skiing. In accordance with this, Danish beginners had an injury ratio about four times those for Norwegian and Swedish beginners. Present or previous skiing instruction reduced the injury ratio significantly only for the Norwegians; no significant differences were observed between the skiers from the three countries regarding binding testing.

The previously reported higher injury risk for Norwegian compared to Swedish alpine skiers no longer exists. This may be due to more information about skiing safety in Norway in the 1980s. The relatively higher injury ratio for the Danes may be due to shorter skiing seasons, but less public information about skiing safety may also have contributed.
Femoral Shaft Fractures Resulting from Alpine Skiing Injuries
Authors: Johnson RJ , Ettlinger CF , Shealy JE
Published: March 2009

This study investigates femoral shaft fractures resulting from skiing accidents occurring at a moderate-sized Northern Vermont ski area over a 15-year interval from 1972 through 1987. Twenty-one skiers sustaining femoral fractures were compared to 5240 other injured skiers who sustained 5678 injuries and a control population. The incidence of femoral shaft fractures was approximately 1 for every 80 000 skier days and was unchanged during the study period. Of the 21 fractures, 17 resulted from bending injuries. There was no evidence to suggest that binding dysfunction contributed to these injuries. Skiers sustaining femoral fractures were found to be similar to the control population in age, height, weight, tibial length, skiing ability, and skiing experience and to use similar skiing equipment. They were taller, heavier, more skilled and experienced, involved in fewer falls, skied faster, more frequently injured in collisions, more likely to have a binding release, and more likely to slide or tumble before their injury than skiers sustaining tibial fractures. The age of skiers sustaining tibial and femoral shaft fractures were similar.
Ski Injury Statistics—What Changes?
Authors: Lamont MK
Published: March 2009

Since 1939, reports on the severity of ski injuries have claimed that downhill skiing is dangerous. The reported injury rate varies from 0.8 to 9.1 per 1000 skier days. Two studies at the same ski field, 28 years apart, gave injury rates of 2.7 and 2.4. This was over the period of greatest development for skiing and ski safety equipment. The reported injury rate in 1939 in Norway was 2.7 injuries per 1000 skier days and in 1988 in New Zealand was 4.7 injuries per 1000 skier days. The mean for that 49-year period was 3.5 injuries per 1000 skier days. The mix of injuries has clearly changed, but the actual rate of injury as measured in injuries per skier day has hardly altered. Is skiing safer now than in 1939, or are the comparisons not equal? Well-designed epidemiological studies are needed to measure true incidence accurately; only then can the effectiveness of safety measures be determined.
Alpine Skiing Injuries: An Epidemiological Study
Authors: Oliver BC , Allman FL
Published: March 2009

To ensure the maximum level of safety for alpine skiers, conditions and factors that predispose to injury need to be identified. This study surveyed potential risk factors for injury in a closed population of skiers using well-defined criteria for injury. Thirteen percent of those skiers answering the survey sustained an injury. The injury rate was 24 per 1000 skier days. Most injuries occurred on the first day of skiing. Icy conditions and fatigue appeared to predispose skiers to injury. The shoulder and knee were the most common anatomical sites of injury. Factors such as age, sex, level of ability, and conditioning, which have been implicated in previous studies as risk factors for injury in alpine skiing, did not appear to predispose the skier to injury in this controlled study.
Pain Threshold Along the Lower Leg in Alpine Ski Boots
Authors: Schaff PS , Ruckdeschl P , Hauser W , Rosemeyer B
Published: March 2009

The pain threshold (PT) along the lower leg was analyzed in both female and male skiers to better understand current sex-related requirements for alpine ski boots. PT was found to be at an average of 32 N/cm2 for the male group and 23 N/cm2 for the female group. The difference between groups was significant (p = 0.05). We found no significant difference in PT distribution along the lower leg within the groups. Lowering the skin temperature more than 10°C resulted in a significantly higher PT. A 40% higher PT was found with twice as large an area used to apply the pressure (p = 0.05). The variation of PT to each subject is comparable to other psycho-physical methods, for example, vibration measurements. Because of a great variation among subjects, a definition of a maximum value to be tolerated in ski boots could not be given within a sufficient confidence interval.

Based on our findings, the following requirements are given: Ski boots must be classified according to sex, because women have a significantly lower PT that may lead to a restriction of motion in a stiff boot designed for male athletes. Temperature isolation for ski boots is very important, not only for comfort but also for safety reasons. Constant sensation feedback, necessary for accurate skiing, is only granted at constant temperature. To avoid pain at low pressure, the force along the lower leg should be distributed homogeneously over a large area. The area of most pressure should not be along the tibialis anterior tendon, because even pressure below the pain level over a long time may lead to a tendovaginitis in that area.
A New Artificial Leg for Ski Boot Testing
Authors: Senner V , Schaff P , Hauser W
Published: March 2009

For years, artificial legs have been used in ski boot testing, mainly for the determination of shaft-stiffness, flexibility range, and pressure distribution. Pressure distribution measurements with the existing standard leg (TUEV prosthesis) showed significant differences from measurements on human legs. This study improves the old prosthesis to get results comparable to a real-life situation. By comparing the individual pressure distribution of 14 male subjects with the group's statistically determined average pressure distribution, the person with the fewest differences from the average distribution curve was found. By rebuilding his lower leg in shape and size, changing the joint position, using a plastic shell to simulate the tibialis anterior, and finally, cushioning it with a flexible material to simulate soft tissue, a new prosthesis was designed that showed a major improvement to the old standard leg.
Ski Boot Thermography Method and Its Significance
Authors: Zucco P
Published: March 2009

Protection from cold is one of the most important functions considered in designing and manufacturing ski boots. Thermography is used for evaluating cold protection capacity of various kinds of inner shoes and boot shells. We performed thermal analysis of three boot categories using two thermography methods, and the results were compared. We observed that (1) thermography is a valid method for boot cooling studies; (2) both an inner shoe and boot shell aid in thermal insulation; (3) progressive cooling and forced warming of the boot give the same results in identifying heat exchange areas; (4) blood flow, muscle activity during skiing, and boot fit must be considered in designing ski boots; and (5) because of the importance of this boot function, a standardized method of analysis should be adapted by all manufacturers. We concluded that the structure must be analyzed with thermography testing. It is not necessary to use an artificial limb inside the boot to obtain satisfactory data.
A Model for the Turning Snow Ski
Authors: Renshaw AA , Mote CD
Published: March 2009

A model is developed to investigate the steady-state solutions of a turning snow ski. A rigid body skier executes a constant radius turn on a horizontal snow surface. Two types of forces are assumed along the ski bottom: skidding forces, which arise when shearing a new snow surface, and carving forces, which maintain the curvature of the ski as part of the running surface of the ski slides along its own track without shearing the snow. Using the equations of conservation of linear and angular momentum, dynamic equilibrium is established for the three forces and accelerations acting on the skier/ski system: the force generated along the flexing ski, gravity, and the centripetal acceleration of the turn. Turn radius and speed are insufficient to specify a unique solution to these equations. To quantify the effects of different ski designs on the model, a range of possible dynamic equilibrium solutions is calculated for each turn radius and speed and compared using two indices, one measuring the mechanical efficiency of the turn resulting from the energy dissipation of shearing the snow surface, and the second measuring the equilibrium solution sensitivity to human control and regulation. When possible solutions are mapped onto the plane of these two indices, a characteristic solution behavior emerges, which has been corroborated with experimental results found using a model ski turning on Astroturf.® This behavior provides a quantitative basis for comparing different ski designs and proposing new design strategies.
Behavioral Risk Factors for Ski Injury: Problem Analysis as a Basis for Effective Health Education
Authors: Bouter LM , Knipschild PG
Published: March 2009

A problem analysis dealing with the importance of behavioral risk factors for ski injuries is based on the results of a case-control study conducted among Dutch skiers. In this study, cases (N = 572) were a sample of those who filed insurance claims for medical costs incurred as the result of a ski injury that prevented them from skiing for more than one day. Controls (N = 576) were a sample of uninjured skiers who filed insurance claims for nonmedical reasons.

Not taking ski lessons appeared to be a risk factor among beginners (odds ratio [OR] = 2.5; etiologic fraction [EF] = 12%). Failure of bindings to release is associated with a higher risk (OR = 3.2) for lower extremity injury, indicating that optimal binding adjustment can have a substantial preventive effect. Surprisingly, binding adjustment in the Netherlands more often involved the use of a test device compared to the ski resorts involved. In the latter case, the injury risk was higher (OR = 1.6; EF = 17%). From our data and the available literature, it can be concluded that alcohol consumption is probably not an important risk factor for ski injury. Several findings from our study seem to indicate that risk underestimation may be a risk factor for ski injury, but further study is necessary on this point. Taken together, the empirical basis for behavioral risk factors other than those mentioned above is still rather weak and thus a restrictive policy with respect to health education for downhill skiers would seem appropriate.
Comments on Engineering Needs and Wear Models
Authors: Bayer RG
Published: March 2009

Engineering applications can involve complex tribological considerations other than the ranking and selection of materials. These can include such aspects as assessment of the significance of a variety of design parameters, determination of tolerances for these parameters, comparisons of designs, and life projections. Several of these are illustrated in terms of actual situations encountered by the author, along with the methods used to address these aspects in those cases. The typical needs of such applications of tribology are identified, and current approaches in wear modeling and wear testing are compared to these needs. Inadequacies are identified and suggestions as to how to address these are made. In addition, the differences between a material engineering and a more general design approach to engineering problems are identified, and the significance of these in terms of modeling and testing are discussed.
Design of Plain Bearings for Heavy Machinery
Authors: Glaeser WA
Published: March 2009

A design system for heavily loaded, slow moving, grease lubricated plain bearings has been developed. The system is based on frictional input and dissipation analysis combined with experimental data. P-V design charts have been developed which show regions of high friction, excessive bearing temperature, high wear, and moderate wear. The information presented in the design charts compares well with full bearing test results.
The Structure of Erosive Wear Models
Authors: Bahadur S
Published: March 2009

The complexity of the erosion process and the difficulty in modeling it are discussed. As for the complexity, the multiplicity of factors that affect the erosion process are described and the effect of these parameters in the context of erosion modeling is considered. The mechanisms of erosion that have led to the development of models are discussed. The erosion models based on different approaches are presented. Some of these models are based on the empirical approach while others are based on the concepts such as cutting, low-cycle fatigue, adiabatic shear and the like. The heterogeneity of these models is examined and the difficulty and limitations in their application to practical erosive situations are discussed. The directions for future work in the context of modeling are provided. Some suggestions are made to assist the designers in designing against erosion.
Success and Failure of Simple Models for Abrasive Wear
Authors: Larsen-Basse J
Published: March 2009

The abrasive wear process is often thought to be a form of simple microcutting and to be quite easy to model. Yet, only very qualitative rules of thumb exist for purposes of design life calculations, materials selection and materials development. A simple model based on hardness has had some success when used for general comparisons of similar materials worn under similar conditions. However, it has a number of limitations which must be clearly understood in order to use it in a global sense. The potential for developing a concise model of more universal applicability and the need for such a model are explored.
Wear by Chemical Reactions in Friction Contacts
Authors: Lauer JL
Published: March 2009

In friction contacts chemical reactions can occur between the surrounding fluid and the solid surfaces in unusual ways. Overcoats are formed on and partly or wholly removed from the surfaces by wear. Reactions between the substrate and/or the overcoat and the environment become diffusion-controlled and can even become oscillatory. Analysis of diffusion-controlled reactions shows that faster-than-expected reaction rates can result from tribologically thinned overcoats. Further reactions of the overcoats and their mechanical removal can be modeled in ways used in biology to depict population changes as growth rates of predators and prey. Examples are simultaneous sulfiding and oxidizing of steels at low temperatures (< 100°C) and the formation of carbonaceous layers on both metals and ceramics by carbon-containing gases in various temperature ranges between ambient and 700°C.
Considerations on Data Requirements for Tribological Modeling
Authors: Ruff AW
Published: March 2009

An idealized database for tribology is described that contains numeric data with characteristics needed for use in modeling approaches in tribology. Tribological data on materials are considered in detail, and other types of required data are identified. Testing methodologies for obtaining data are examined. Priority areas for future work in data gathering and data evaluation in tribology are suggested.
Classification of Metallic Materials from a Viewpiont of Their Antiwear Behavior
Authors: Sasada T
Published: March 2009

The mode of dry sliding wear of metals is classified as severe wear or mild wear. From a distinct difference between wear rates in the severe and mild wear, it is deduced that the most important character to be possessed in “antiwear materials,” is that the wear mode must be mild wear. Severe wear appears in most all metallic materials. The metals in which mild wear appears are, on the contrary, limited. The mild wear is promoted by chemisorption of oxygen molecules onto fresh surfaces generated during wear processes. Backed with this fundamental principle, it is deduced that the elemental metals in which mild wear appears are transition metals includung rare earth metals, because these metals have a high chemisorption activity for surrounding gas molecules. Extending this theory to materials other than pure elements, it is deduced that semiconductors, some ceramics, amorphous alloys, quenched steels and some intermetallic compounds can be classified as antiwear materials.
Wear Transition Surfaces for Long-Term Wear Effects
Authors: Yust CS
Published: March 2009

Tribologists tend to present friction and wear data as tabulations of values for specific ranges of test conditions. The conditions generally involve short test durations and express system loads in terms of applied forces. The designer, on the other hand, is concerned with stress levels and component durability, in particular time to failure. Because machine components are frequently exposed to cyclic stress conditions, fatigue effects cannot be ignored, especially in non-metallic materials containing residual flaw populations. Wear maps and transition diagrams are emerging as a convenient means of summarizing and presenting wear data in a form useful to designers. An extension of one of the diagrams to incorporate the effects of time on wear response is proposed and discussed.
Wear Modeling : How Far Can We Get with First Principles ?
Authors: Godet M , Berthier Y , Lancaster J , Vincent L
Published: March 2009

A brief description of what is meant by “wear modeling for design,” is given. The three contributors or triplet that must be considered in any wear modeling attempt are identified. These are : - mechanisms : i.e. all systems in which one or more contacts are established. Quasi-static liaisons such as gaskets, high speed bearings and gears are examples of mechanisms. - first-bodies : i.e. the rubbing elements of each mechanism; gear teeth, balls, races and cable strands, are examples of first-bodies. - third-bodies : i.e. any material, whether natural or artificial, which separates the rubbing first-bodies. Solid and liquid lubricants and debris beds are examples of third-bodies.

The diversity of conditions (loads, speeds, temperatures, environments) encountered in different mechanisms, the differences noted in stress and temperature fields found in first-bodies, the variations in composition and rheology observed in third-bodies are highlighted.
ALUSELECT—Engineering Property Data for Aluminium Alloys
Authors: Sandström R , Schönholzer P , Moosavi E
Published: March 2009

In a collaborative effort between eight major European aluminium companies, property data for aluminium alloys have been collected, evaluated, and new harmonized values proposed. The following property groups have been considered: conventional mechanical, physical, creep, fatigue, corrosion resistance, cold formability, welding, machinability, and properties for surface treatment. The collected property data have been input into a data bank called ALUSELECT. Using the data bank, the property data have been analyzed and the results of the analysis used for the harmonization process. The harmonized values have also been input in the data bank. The harmonized property values will become available to the public in 1991, also in machine readable form. In this way, it is expected that data bank builders should have access to good property data information for aluminium alloys. A simple selection system with the harmonized property data will be also provided.
Materials Designation Systems: Their Problems and Possible Solutions
Authors: Reynard KW
Published: March 2009

The VAMAS (Versailles Project on Advanced Materials and Standards) Technical Working Area 10, Materials Data Banks, has a project on materials designation systems in progress at the present time. The author is coordinator of this project that seeks to produce a world-wide inventory of materials designation systems. With it there will be a guide describing the method by which each system works, how new designations are assigned and by whom, and the conflicts and pitfalls of which users of multiple systems are often unaware.

As a growing reliance is placed upon information from computerized sources and more design and manufacturing processes are linked directly to numerical data banks, so the dangers from a lack of expertise and knowledge in the total system increase. Data exchange across the man-computer and the computer-computer interfaces rely increasingly on a lack of ambiguity and lack of uncertainty in the terminology and labels attached to the information.

In the western world, this situation may be aggravated by falling numbers of scientists and engineers in industry and the increasing numbers of computers. While a computerized system is more capable of producing repeatable results, it is also more likely to make connections that might either not be made other than by an expert, or might in some cases be rejected by an expert. Some of these connections could be advantageous, and some, disastrous if they go undetected.

A computer search for data on a material using the string 356 could produce numbers that relate to a brass, a steel, or an aluminum alloy. The response might be appreciated by some users but not necessarily by another computer program.

There needs to be greater understanding of the present situation with a view to constructing the appropriate interfaces and safeguards, and to reducing the complexity at the source.

The paper reviews items of interest from the project and the possible methods of dealing with the problems.
The Role of Metadata in the Design and Operation of a Materials Database
Authors: Westbrook JH , Grattidge W
Published: March 2009

A rich set of metadata is required to integrate data values into a materials data-base. These metadata range from descriptions of the materials involved, the properties, independent variables, units, source of the data value, associated statistical descriptors, footnotes, and references. They are necessary to ensure the integrity of the database, to provide compatibility of data values arising from different sources, and to accommodate the diverse backgrounds of users with respect to terminology usage. The metadata issues covered include: materials characterization, terminology and standardization, implicit metadata in printed exhibits of data values, problems of developing a metadata thesaurus, testing for completeness of canonical or basic data records, use of metadata in data entry, and the identification of hypertext links for materials databases. Resolution through coordinated standardization of terminology and consistency of metadata will ensure further development of compatible materials databases.
Access Paths for Materials Databases: Approaches for Large Databases and Systems
Authors: Rumble J
Published: March 2009

Materials databases can contain widely differing data records in terms of the size and number of data elements, depending on the types of data. In using materials databases, users often want to search an entire database as if all data for one material were in one record, even though physically and logically they are in many records. This affects search strategies and their implementation. Acceptance of materials databases depends on user interfaces containing search strategies that will find answers to queries as needed by engineers and scientists. This paper will outline typical access paths (search strategies) from three points of view: first, simple and complex matching; second, specification of multiple criteria; and third, search refinement.
The Development of a Computerized Materials Properties Database Management System
Authors: Gall TL , Heller ME , Cverna F
Published: March 2009

The development of a computerized materials properties database management system is summarized. Attention is given to the database format and capabilities of the software system. Also discussed are the criteria and procedures employed to locate and review data for inclusion in the database.
Water Intrusion in Barrier and Cavity/Rain Screen Walls
Authors: Williams MF , Williams BL
Published: March 2009

Exterior walls are designed and constructed using barrier or cavity/rain screen wall principles. Exterior Insulation and Finish Systems (EIFS) are typically constructed as barrier walls; masonry is often constructed as a cavity wall. These wall systems are discussed along with common deficiencies that allow water intrusion to occur.
Water Vapor Behavior in Exterior Insulation and Finish Systems
Authors: Thomas RG
Published: March 2009

Exterior Insulation and Finish Systems (EIFS's) are a type of cladding for exterior building walls. They are attached to the outside face of the wall structure. EIFS's were developed in Europe where exterior wall structures are predominantly unit masonry and concrete. In America, EIFS's are usually attached to lightweight wall structures of studs and gypsum sheathing.

In America, EIFS's are used in a wide range of climate conditions, including air conditioned buildings in hot, humid climates as well as arctic conditions. EIFS's are used in virtually every type of building including residential and high-rise commercial structures. Because of their light weight and relatively short track record, the longevity of EIFS's has been questioned. In particular, the effects of water from both liquid and water vapor sources is a concern. This concern has come from both field experience and theoretical analysis.

The American way of using EIFS's results in different water vapor behavior in the wall assembly. Condensation can occur in different locations in the wall under different conditions. The effects of water on the wall can be pronounced. The durability of the wall can be greatly affected if water vapor problems occur.

This paper reviews the American style of using EIFS's on light weight wall structures in terms of water vapor flow behavior. A computer program is used to demonstrate various conditions that affect the development of condensation in EIFS wall systems. The paper identifies common American wall designs that require attention and offers solutions for dealing with water vapor problems.
Heat and Moisture Transport Through a Glass-Fiber Slab with One Side Subject to a Freezing Temperature
Authors: Tao Y-X , Besant RW , Rezkallah KS
Published: March 2009

Experiments were performed of heat and moisture transport through a glass-fiber slab to investigate the effect of condensation and frosting on the thermal performance of insulation. The slab has one side impermeable and subject to a cold temperature (below the triple point of water) and the other side open to a moist air at a room temperature and for various humidity levels. The accumulation of moisture and frost results in an increase in heat loss up to a maximum of twice as much as that for a dry insulation. A comparison between a one-dimensional, numerical model based on a formulation of vapor diffusion in porous media and the experimental results, reveals that significant hygroscopic effects occur in the experiment for initially oven-dried specimens, and contribute to the discrepancy between the transient results of the prediction and of the experiments. For the transient processes, the differences in predictions, excluding the adsorption phenomenon, and the experimental data can lead to a maximum discrepancy of 26% in temperature and of 35% in heat flux.
Vapor Control and Psychrometric Monitoring in Exterior Walls
Authors: Kudder RJ , Hoigard KR
Published: March 2009

Curtain walls may contain a cavity between the interior finish wall and the exterior cladding. Condensation can occur in this space as interior moisture enters either through direct air leakage paths or diffusion through construction materials, and can significantly affect the facade life expectancy. Buildings exhibiting facade degradation due to cavity moisture generally require detailed evaluation in order to determine the source, and to develop an appropriate repair plan. One tool available to the investigator is field testing. This paper will address typical wall behaviors and the practical aspects of field instrumentation to acquire data for determination of the presence or absence of cavity condensation, and a time history of its occurrence.
Sealant Joint Design
Authors: Beall C
Published: March 2009

Sealant joint failures usually result from either inadequate provisions for movement, improper selection and use of materials, poor workmanship, poor detailing, or combinations of these problems. The proper design of sealant joints includes not only movement calculations and material selection, but planning and detailing to provide overall moisture control, and specifying to assure proper installation. This paper discusses three common joint types, and outlines the primary variables involved in the design of moving joints. Tables of thermal and moisture expansion coefficients are given, and various formulas used for calculating movement are discussed, along with differential movement potential and construction tolerances. An analysis of generic sealant types and characteristics is given, with an emphasis on substrate compatibility, sealant performance and selection. The sum of the information represents a set of criteria which will assist practicing architects and engineers in the joint design process.
Water Infiltration in Hawaii and Ensuing Construction Litigation
Authors: Yanoviak AC
Published: March 2009

Hawaii has its share of water infiltration problems and remedial repair solutions that have also resulted in significant failures attributed to improper design and construction of exterior building walls. Hawaii also has its share of design and construction lawsuits and apportioned culpability. It is well known that this can be a very expensive way to learn, as it affects profitability. It has become increasingly apparent that in many instances the building codes and standards are minimal at best.
Computer Simulation of Wall Condensation Problems
Authors: Carlson AR
Published: March 2009

Field reports from colder climates such as Alaska, Minnesota, Ohio, etc. indicate that wall moisture is a major problem, if there is no vapor retarder. A polyethylene vapor retarder is recommended in Alaska. Studies of retrofitted walls in older residences from warmer climates such as Oregon intimates that moisture in the wall may not be a problem even though there is no vapor retarder. However, the Oregon study still recommends a polyethylene vapor retarder for new construction.

There are two potential vapor retarders, which are designated in this paper as the primary and secondary vapor retarders. The primary vapor retarder for heated buildings, in cold climates such as Alaska, should consist of a polyethylene membrane placed at the inner skin directly under the gypsum wallboard (drywall). If the primary vapor retarder does not function as intended, then the outer skin consisting of a combination of plywood sheathing, siding, wind barrier, etc., may function as a secondary vapor retarder, which may trap moisture in the wall cavity.

Computer spreadsheet simulations of various wall sections indicate that wall moisture problems are dependent on inside and outside psychrometric conditions. The vapor pressure differential of the inside and outside air determines the driving force of the vapor. The vapor pressure and permeability of the primary and secondary vapor retarders determines how much water vapor may diffuse into the wall cavity. If the temperature gradients at the vapor retarder remains below dew point the moisture will condense in the cavity. If the temperature in the cavity remains below 32°F for prolonged periods the condensate will freeze and continue to build up as frost.
The Upper Bounds of Reduced Axial and Shear Moduli in Cross-Ply Laminates with Matrix Cracks
Authors: Lee J-W , Allen DH , Harris CE
Published: March 2009

The present study proposes a mathematical model utilizing the Internal State Variable (ISV) concept for predicting the upper bounds of the reduced axial and shear stiffnesses in cross-ply laminates with matrix cracks. The displacement components at the matrix crack surfaces are explicitly expressed in terms of the observable axial and shear strains and the undamaged material properties. The reduced axial and shear stiffnesses are predicted for glass/epoxy and graphite/epoxy laminates. Comparison of the model with other theoretical and experimental studies is also presented to confirm direct applicability of the model to angle-ply laminates with matrix cracks subjected to general in-plane loading.
Effects of Moisture Absorption on Edge Delamination, Part I: Analysis of the Effects of Nonuniform Moisture Distributions on Strain Energy Release Rate
Authors: Hooper SJ , Toubia RF , Subramanian R
Published: March 2009

The effects of a nonuniform moisture distribution on the edge delamination of composite laminates were analyzed. The analysis was performed using a laminated plate theory analysis and a quasi-three-dimensional finite element method. The total strain energy release rate and its mixed mode components were evaluated for both uniform and nonuniform moisture distributions, and the corresponding results were compared. Both of the analyses employed a Fickian diffusion model to determine the hygroscopic concentration profile across the thickness of a laminate.
Effects of T-Tabs and Large Deflections in Double Cantilever Beam Specimen Tests
Authors: Naik RA , Crews JH , Shivakumar KN
Published: March 2009

A simple strength of materials analysis was developed for a double cantilever beam (DCB) specimen to account for geometric nonlinearity effects due to large deflections and T-tabs. A new DCB data analysis procedure was developed to include the effects of these nonlinearities. The results of the analysis were evaluated by performing DCB tests on materials having a wide range of fracture toughnesses. The composite materials used in the present study were T300/5208, IM7/8551-7, and AS4/PEEK.

Based on the present analysis, for a typical load-point deflection/crack length ratio of 0.3 (for AS4/PEEK), T-tabs and large deflections lead to a 19 and 6% effect, respectively, in the computed Mode I strain energy release rate. Design guidelines for DCB specimen thickness and T-tab height were also developed in order to keep effects due to these nonlinearities within 2%.

Based on the test results, for both hinged and tabbed specimens, the effects of large deflection (compared to linear DCB results) on the Mode I fracture toughness (GIc) were almost negligible (less than 1%) in the case of T300/5208 and IM7/8551-7; however, for AS4/PEEK, the effect was from 2 to 3%. The effects of T-tabs (compared to a linear DCB with tabs) on GIc were more significant, with T300/5208, IM7/8551-7, and, AS4/PEEK showing a 5, 15, and 20% effect, in that order.
Initiation and Growth of Mode II Delamination in Toughened Composites
Authors: Russell AJ
Published: March 2009

The origins of nonlinearity in the Mode II delamination fracture of three organic matrix, carbon fiber composite materials was investigated. This was accomplished by testing specimens with different types of starter cracks and by loading and unloading these specimens several times so that the change in nonlinearity as the delaminations grew could be measured. The load at which crack growth initiated was determined by acoustic emission. Slow crack growth was found to be the principal cause of nonlinearity in the materials tested. The crack velocity obeyed the same power law dependence on GII as has been observed for slow crack growth in visco-elastic polymers. For the first loading from the end of the starter cracks, plastic deformation at the crack tip also contributed to the nonlinearity. Other sources of nonlinearity included an increasing fracture resistance in one of the materials as well as problems associated with producing a clean, sharp starter notch with a straight crack front. The implications of these findings to the use of linear elastic fracture mechanics for predicting delamination behavior of these materials and to the measurement of Mode II interlaminar fracture toughness are also discussed.
Evaluation of the Split Cantilever Beam for Mode III Delamination Testing
Authors: Martin RH
Published: March 2009

A test fixture for testing a thick split cantilever beam for scissoring delamination (Mode III) fracture toughness was developed. A three-dimensional finite element analysis was conducted on the test specimen to determine the strain energy release rate, G, distribution along the delamination front. The virtual crack closure technique was used to calculate the G components resulting from interlaminar tension, GI, interlaminar sliding shear, GII, and interlaminar tearing shear, GIII. The finite element analysis showed that at the delamination front no GI component existed, but a GII component was present in addition to a GIII component. Furthermore, near the free edges, the GII component was significantly higher than the GIII component. The GII/GIII ratio was found to increase with delamination length but was insensitive to the beam depth. The presence of GII at the delamination front was verified experimentally by examination of the failure surfaces. At the center of the beam, where the failure was in Mode III, there was significant fiber bridging. However, at the edges of the beam where the failure was in Mode II, there was no fiber bridging and Mode II shear hackles were observed. Therefore, it was concluded that the split cantilever beam configuration does not represent a pure Mode III test. The experimental work showed that the Mode II fracture toughness, GIIc, must be less than the Mode III fracture toughness, GIIIc. Therefore, a conservative approach to characterizing Mode III delamination is to equate GIIIc to GIIc.
Combined Effect of Matrix Cracking and Free Edge on Delamination
Authors: Salpekar SA , O'Brien TK
Published: March 2009

The effect of the stress-free edge on the growth of local delaminations initiating from a matrix crack in a composite laminate is investigated using a three-dimensional finite element analysis. Two glass epoxy layups, (02/904)s and (±45/904)s, were modeled with a matrix crack in the central group of eight 90° plies, and delaminations initiating from the matrix cracks in the 0/90 and -45/90 interfaces, respectively. The analysis indicated that high tensile interlaminar normal stresses were present at the intersection (corner) of the matrix crack with the stress-free edge, suggesting that an opening (Mode I) delamination may initiate at these intersections.

In order to analyze the strain energy release rates associated with delaminations that may form at the corners, three different configurations of the local delamination were assumed. One configuration was a uniform through-width strip growing normal to the matrix crack in the direction of the applied load. The other two configurations were triangular shaped delaminations, originating at the intersection of the matrix crack with the free edge, and growing away from the corner. The analysis of the uniform delamination indicated that the magnitude of both the total strain energy release rate, GT, and its components increased near the free edges. This edge effect was symmetric for the (02/904)s layup. However, for the (±45/904)s layup, the G distribution across the front was asymmetric, with the total G and its components having higher values near one free edge than the other. For both layups, the GI component was large at small delamination lengths, but vanished once the delamination had reached a length of one-ply thickness.

The second and third delamination configurations consisted of triangular-shaped delaminations with straight fronts inclined at angles of 10.6 and 45°, respectively, to the matrix crack. The total G along the delamination front decreased sharply near the matrix crack for both configurations and increased sharply near the free edge for the 10.6° configuration. However, the total G distribution was fairly uniform in the middle of the delamination front for the 10.6° configuration. These inclined models suggest that if the exact geometry of the delamination front could be modeled, a uniform G distribution may be obtained across the entire front. However, because the contour of the delamination front is unknown initially, it may only be practical to model the uniform through-width delamination and use the peak values of G calculated near the free edges to predict delamination onset. For the layups modeled in this study, the total G values near the free edge agreed fairly well with a previously derived closed-form solution. However, a convergence study may need to be conducted to have confidence that peak values of G calculated from three-dimensional finite element analyses near the free edges are quantitatively correct.
Delamination Analysis of Tapered Laminated Composites Under Tensile Loading
Authors: Armanios EA , Parnas L
Published: March 2009

A study was conducted to analyze tapered composite laminates under tensile loading. A tapered construction made of S2/SP250 glass/epoxy laminate was used to achieve a thickness reduction using three consecutive dropped plies over a distance of 60 ply thicknesses. The principle of minimum complementary potential energy was used to determine interlaminar stresses. The interlaminar peel stress distribution shows a higher tensile intensity at the taper/thin portion juncture. The total strain energy release rate is determined using a simplified membrane model. Results are compared with a finite element simulation.
Analysis of Delamination Growth in Compressively Loaded Composite Laminates
Authors: Tratt MD
Published: March 2009

An analytical and empirical study was conducted to investigate delamination behavior in composite structures.

The objective of the analysis was to predict the threshold stress for the initiation of delamination growth in compressively loaded composite laminates. MSC/NASTRAN geometrically nonlinear finite element analysis and a virtual crack opening technique were used to compute strain energy release rate distributions around circular delaminations. The distributions were computed for various compressive stress levels and the threshold stress for delamination growth was then determined by applying the strain energy release rates in a mixed-mode fracture criterion.

A number of static compression tests were conducted on specimens made from AS4/3501-5A graphite fabric-reinforced epoxy. The specimens contained circular delaminations of various sizes. The delaminations had been created by implanting Teflon inclusions in the prepreg layup.

Computed predictions of the delamination growth threshold stresses were significantly in error relative to the test data. The analysis did, however, concur with observed trends and provided qualitative insight into the process of quasi-static delamination growth.
A Study of an Implanted Delamination Within a Cylindrical Composite Panel
Authors: Palazotto A , Wilder B
Published: March 2009

This research studied the effects of an inserted circular delamination on the strength of an eight-ply, quasi-isotropic composite laminate. Cylindrical panels were loaded compressively, and the global buckling load of the delaminated plies were examined. It was found that, for the level of delamination defect investigated, a linear bifurcation analysis gave fairly accurate predictions of the global panel strength. Load values, which caused local instabilities in the region of panel damage, were also recorded and compared to an approximate analysis.

During the experimental phase of this research, certain physical responses of the panels led to a set of simplifying assumptions. It was thought that there existed a value of strain that when applied to a circular delamination would cause the sublaminate to buckle. The value of strain in the sublaminate should be related to a value of strain in the curved panel. Some method of relating these two values of strain was suggested by the results of experimental tests.