bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparison of Experimental Observations and Numerical Predictions for the Initiation of Fiber Microbuckling in Notched Composite Laminates
Authors: Guynn EG , Bradley WL , Ochoa OO , Whitcomb JD
Published: March 2009

Previous experimental observations indicate that the compressive failure of open-hole multidirectional thermoplastic composites begins with in-plane fiber microbuckling at the hole. Growth of this damage requires little additional load, suggesting that compressive strength is controlled by initiation, rather than propagation, of in-plane microbuckling. The significant role of local constraint on the initiation of fiber microbuckling is indicated in this work.

Stacking sequence and resin ductility (varied as a function of the test temperature) are the two primary variables in this investigation, both of which provide systematic variation of support to the load-bearing 0° plies. The material system selected for this investigation is a thermoplastic composite, APC-2: AS4/PEEK.

The compression specimens used are 2.54 cm wide with a 2.54 cm long gage length. Each specimen contains a 0.3175-cm-diameter semicircular notch at each free edge, centered along the gage length. This polished notch facilitates the observation of the initiation of damage in the form of in-plane fiber microbuckling into the notch. High-temperature tests are conducted using a controlled forced-air heat gun rather than an environmental chamber to allow high-magnification observation of the failure processes at the higher temperatures.

Geometric and material nonlinear two-dimensional finite element analysis is used to model the effects of the initial fiber waviness in combination with matrix nonlinearity on the fiber microbuckling initiation strain levels and the resulting shear strain developed in the matrix.
Compression Testing of Thick-Section Composite Materials
Authors: Camponeschi ET
Published: March 2009

As composite materials become more attractive for use in large Navy structures, the need to understand the mechanical response of composites greater than 6.4 mm (0.25 in.) in thickness becomes a necessity.

In this program, a compression test fixture that allows the testing of composites up to 25.4 mm (1 in.) in thickness and greater was designed and refined. This fixture was used to evaluate the effects of constituents, fiber orientation, and thickness on the compressive response of composite materials. In addition, the fixture was used to determine if the failure mechanisms observed for thick composites are similar to those that have been observed and reported for composite materials less than 6.4 mm (0.25 in.) thick.

The in-plane moduli, in-plane and through-thickness Poisson's ratios, compression strength, and failure mechanisms of the thick composites were shown to be independent of material thickness. The predominant failure mechanisms for both materials were kink bands and delaminations, and were identical in geometry to those that have been reported for composite materials in the range of 2.54 mm (0.1 in.) thick.

Although unchanged with thickness, the through-thickness Poisson's ratio for the carbon- and glass-reinforced laminates were found to be significantly nonlinear, resulting in changes in this property of up to 58% from the initial region of the strain-strain curve to the final region of the strain-strain curve.
Influence of Low-Velocity Impact on Composite Structures
Authors: Madan RC
Published: March 2009

Composite materials are sensitive to out-of-plane loads because they are weaker through the thickness than in the plane of lamination. Consequently, composite structure subjected to impact may suffer significant damage, which results in a loss in strength. The effect of impact energy on different thicknesses of laminate with respect to ultimate compressive strength was evaluated using the NASA ST-1 specimen test. Impact damage was measured using ultrasonic C-scans and quality was assessed by visual observations. A semiempirical model for impact damage was proposed to determine residual strength in terms of laminate properties, static influence coefficients, and impact energy.

To determine residual compression strength, single- and multiple-impact damage was inflicted on bonded stiffened structures. The results were verified by the residual strength method, which uses laminate properties and measured damage size to predict the residual strength of composites. The correlation between predicted and actual strength was very encouraging. Although the damage was inflicted with different impactor masses, velocities, and impact energy, the data indicated that residual strength is a function only of damage present and does not reflect the manner in which the damage is inflicted. Finally, a semiempirical relationship was developed for damaged areas in stitched laminates.
Response of Composite Plates to Quasi-Static Impact Events
Authors: Bucinell RB , Nuismer RJ , Koury JL
Published: March 2009

A two degree of freedom, spring-mass model is used to investigate the response of filament-wound composite plates subjected to transverse impacts. From this model, it is concluded that it is the ratio of impactor to target frequencies that determines whether the structural response to impact is quasi-static or dynamic in nature. In addition to the model development, a test matrix is designed to isolate the effects of impactor mass, velocity, and energy on quasi-static impact response and damage formation. These data compared well with the model predictions.
Compression of Composite Materials: A Review
Authors: Camponeschi ET
Published: March 2009

This paper is a literature review of research on the compressive response of fiber-reinforced composite materials. The review is organized by subject and the papers are included in one of three main sections; (1) Compression Test Methods, (2) Failure Theories and Failure Mechanisms, and (3) Experimental Investigations. The compression test method section includes a discussion of 15 compression test methods. The section on failure theories and failure mechanisms discusses failure theories and observations including those dealing with fiber microbuckling, transverse tension failure, and fiber kink-band formation. The section on experimental investigations summarizes data that is available in the literature. Tables are presented that list information on the evaluation of test methods and summarize experimentally developed data. These tables provide an index for quick reference to the research discussed in this paper.
Damage-Based Notched Strength Modeling: A Summary
Authors: Kortschot MT , Beaumont PWR
Published: March 2009

The effect of subcritical damage on the notched strength of cross-ply graphite-epoxy specimens has been studied using 914C/T300 laminates of the family (90j/0j)ns (j = 1,2, n = 1,2,4). Damage was monitored using quasi-real-time radiography and dynamic scanning electron microscopy. In addition, the strain field in the vicinity of the notch tip was mapped using a high-resolution optical technique. A strong relationship between subcritical damage and notched strength is evident in all of the data. A theoretical model that is based on observed damage is briefly summarized. Finite element analysis was used to determine the effect of splitting and delamination on the stress distribution in the 0° ply. All specimens were found to fail when the maximum stress in the 0° ply equaled the strength of this ply. The model predicts the effect of both notch size and layup on strength without the need for empirical parameters.
Hole Effect and Compression Fatigue of T300/N5208 Composite Materials
Authors: Lai D , Bathias C
Published: March 2009

Mechanical testing of notched high-performance composites were performed in compression. The compact tension specimen is modified to be used in compression loading. It is shown that the strain energy released rate is an appropriated criteria in compression. A model of the fatigue damage zone is proposed.
Fatigue Failure Processes in Aligned Carbon-Epoxy Laminates
Authors: Piggott MR , Lam PWK
Published: March 2009

Experiments carried out on aligned carbon fiber-reinforced epoxies published elsewhere show that during tensile-tensile fatigue the slope of the S-N curve, β, is increased by reducing the adhesion between fibers and polymers, and decreased by reducing the internal microstresses in the composite. Also, β is increased by plasticizing the polymer. During fatigue, the flexural modulus decreases at a greater rate than the tensile (Young's) modulus. The Poisson's ratio and the hysteresis loop energy both increase during fatiguing. Circular holes drilled in the specimen become gradually more elliptical, with the major axis at right angles to the stressing (and fiber) direction. Final failure involves extensive splitting, and scanning electron microscopic examination of the fractures reveals powdered polymer present on the fracture surfaces. These results suggest that initial fiber waviness may be important. At the antinodes of the waves, there are transverse stresses which could lead to fiber debonding and splitting of the matrix. Once debonded, the fibers could slide within the debonded regions, giving rise to matrix attrition. The cyclic stressing could then cause the powdered matrix thus formed to vibrate and gradually transfer itself to the inside of the curves of the fiber profiles, increasing the fiber curvature (and hence increasing Poisson's ratio, and the width of the hole in the specimen and accounting for the decline in Young's modulus). Eventually the fiber curvature could increase to such an extent that the resulting flexural stresses, combined with the tensile stresses, are enough to cause fiber failure in the regions where this process has developed farthest. Then final failure could occur by connection of these regions through splits in the matrix. (These splits must also develop continuously during fatigue, to account for the gradual loss in flexural modulus.) The process is accelerated by poor fiber-matrix adhesion, and slowed down by reducing the internal stresses which are present due to the cure shrinkage of the resin.
Thermomechanical Fatigue of a Quasi-Isotropic Metal Matrix Composite
Authors: Majumdar BS , Newaz GM
Published: March 2009

In-phase thermomechanical fatigue (TMF) and elevated temperature isothermal fatigue (IF) experiments were conducted on a [0,±45,90]s Ti 15-3/SCS6 composite under load control. A correlation was obtained between the stabilized mechanical strain range and TMF life. TMF life was found to be significantly shorter than IF life when comparisons were made either on a stress-range or a gross mechanical strain-range basis. Damage modes were investigated using optical and scanning electron microscopy. The primary damage mode in IF specimens was transverse microcracking oriented perpendicular to the loading axis. In TMF specimens, although similar damage was observed very close to the fracture surface, the primary damage modes were inter-ply delamination and fiber-matrix debonding. Limited experiments were performed where damage was monitored using a replication technique on the specimen edges. These experiments confirmed delamination and debonding in TMF as well as thermally cycled specimens. Wavelength dispersive spectroscopic (WDS) analysis showed carbon-rich zones along many ply-to-ply interfaces, and these zones may have accelerated delamination cracking. Finite element analysis indicated that the maximum delamination stress occurred at the minimum temperature in the TMF experiments. The fatigue data of Ti 15-3/SCS6 composite, from this and other investigations, were plotted in the form of 0° fiber stress range versus logarithm of fatigue life. This phenomenological plot indicated a similar trend for various data sets, but the exact mechanisms remain to be determined.
Effective Crack Lengths by Compliance Measurement for ARALL-2 Laminates
Authors: Wilson CD , Wilson DA
Published: March 2009

As a means of determining a stress intensity factor solution, the compliance properties of an ARALL-2 laminated-sheet composite were investigated. Fatigue crack growth rate (FCGR) tests were conducted on middle crack tension (MT) specimens fabricated from a layup consisting of three sheets of 2024-T3 aluminum bonded together with unidirectional aramid fibers embedded in epoxy. Excellent fatigue crack growth properties are obtained by the presence of unbroken aramid fibers in the wake of the crack tip. These unbroken fibers act as a bridging mechanism to inhibit further crack growth. To quantify the effect of maximum fatigue load on compliance, a series of FCGR tests were performed. An effective crack length was defined to be the length of a through-the-thickness crack with the same compliance level as a fiber-bridged fatigue crack. A specimen slotted with a jeweler's saw was used to simulate a through-the-thickness crack. As maximum fatigue load increased, the difference between surface measured fatigue crack and sawcut crack length increased. Effective crack lengths were determined to be at least 10 mm shorter than surface measured crack lengths for a 76-mm-wide specimen. The bridging zone was estimated to be at least 5 mm. Compliance and stress intensity factor as functions of effective crack length were determined.
Combustion Fundamentals of Low Volatility Materials in Oxygen-Enriched Atmospheres
Authors: Glassman I
Published: March 2009

The different principles underlying ignition, flame spread and mass burning of condensed phase materials are described fundamentally and in detail. Brief analytical developments of the parameters which affect these various aspects of material flammabillty are presented and the major results are interpreted in light of enriched oxygen conditions and metal and polymer combustibility. The limitations of ASTM LOI (Limiting Oxygen Index) and heat release tests are discussed in light of the fundamentals developed.
Test Developments for Polymers in Oxygen-Enriched Environments
Authors: Tapphorn RM , Shelley R , Benz F
Published: March 2009

Two newly developed methods are discussed that examine ignition and flammability characteristics of polymers in oxygen-enriched environments. These methods were tested with three types of polymers (acrylonitrile butadiene, high-density polyethylene, and polytetrafluoroethylene). The first method comprises a tube furnace assembly and a quartz tube through which a test gas is flowed over a polymer sample located in a combustion boat. The combustion gas flowing through the infrared test cell is analyzed for pyrolysis products using a Fourier transform infrared (FTIR) spectrometer. By measuring the spectral characteristics of the reactant products (spectral absorption bands) as a function of the sample temperature, it is possible to determine some of the pyrolysis properties of the materials. Inspection of the sample while the temperature increases is made possible by viewing the sample through an oblique field-of-view angle to the quartz sampling tube. The sample is monitored visually or recorded with a video camera. Visual monitoring for flame emissions allows for positive identification of the auto-ignition temperature (AIT). With the exception of the high-density polyethylene, the AIT results were in good agreement with previously published values. The FTIR spectrometer was demonstrated to be extremely sensitive for characterizing the compatibility of polymer materials with oxygen. The second method discussed is a modification to a Differential Scanning Calorimeter (DSC). This device, which utilizes a silicon photodiode coupled to the DSC chamber via a light pipe assembly, is used to detect radiative flame emissions from a polymer test sample, The modification provides a method of identifying the AIT threshold, while simultaneously measuring endothermic and exothermic responses. The photodiode detector assembly has been adapted for use with the high-pressure DSC cell configuration. The visible wavelength bandpass of the silicon photodiode has a weak response to the radiation heat of the sample or DSC chamber for temperatures under 500 K. Thus, flames with temperatures in excess of 500 K are easily distinguished from the radiative response of the chamber or slow reaction rates (no visible flame emissions). The testing of the DSC demonstrated the merit of using the radiative flame emissions as the primary signature for the identification of the auto-ignition condition. The method reduces or eliminates ambiguity associated with interpretation of exothermic reactions. Thus, the new instrumentation provides viable methods of determining the AIT for polymers in oxygen-enriched environments.
Ignition of Nonmetallic Materials by Impact of High Pressure Oxygen III: New Method Development
Authors: Janoff D , Pedley MD , Bamford LJ
Published: March 2009

The gaseous oxygen pneumatic impact test has been used by NASA to evaluate the suitability of nonmetallic materials in high-pressure oxygen systems. Several studies have been conducted in the past few years to evaluate the repeatability and applicability of the test. These studies showed that the test has an unacceptable degree of variability. It was recommended that new methods be developed for evaluating the suitability of materials for use in high-pressure oxygen systems. A modified pneumatic impact test was developed and evaluated which addresses the problems of the test currently used by NASA. The test system modifications included a view-ported specimen chamber to view ignition, larger volume between the impact valve and the specimen, ability to adjust pressurization time, and a modified specimen size. Test procedure modifications included subjecting the specimen to a single impact (the current NASA test method required 5 impacts per specimen). The ignition properties appeared to be controlled by the autogenous ignition temperatures of the specimen materials. The modified test allowed the prediction of ignitions that have occurred in component tests and in field incidents that the method currently used by NASA would not have predicted. It is recommended that pneumatic impact ignition tests be performed on components in their use configuration, and that thermochemical methods be used for batch/lot qualification of materials.
Automation of Autogenous Ignition Equipment
Authors: Lowrie R , Garcia H , Henningson RL
Published: March 2009

Automation of the AIT equipment for G72 has reduced the operator attendance time during a test from up to two hours to 15 minutes. The testing is controlled by an IBM XT computer operating through an A/D converter board that receives signals from sensors and sends signals to operate valves and switches. The system components were upgraded in oxygen compatibility and pressure rating to allow oxygen pressures to 34.5 MPa (5000 psig).

After sample installation and a leak check, the computer controls the heating rate and records pressure and temperature. Sample ignition is detected as a temperature rise of more than 2°C/s for 5 s. One minute after this is detected, the heater is switched off, and combustion products are purged from the reaction vessel. The test is ended if no reaction is detected when 425°C (800°F) is reached.

The test data are recorded on a hard disk and can be viewed at any later time. Data obtained on several standard materials are very reproducible. Their standard deviations are all less than 2°C.
Reaction Sensitivities of Al-Li Alloys and Alloy 2219 in Mechanical-Impact Tests
Authors: Simon NJ , McColskey JD , Reed RP , Gracia-Salcedo CM
Published: March 2009

Open-cup and pressurized mechanical impact tests were conducted at White Sands Test Facility (WSTF) on Al-Li alloys (2090, 8090, and WL049) and Al alloy 2219 in various tempers. Pressure, drop height (potential energy), and environment [gaseous (GOX) or liquid (LOX)] oxygen were variables in the test program.

Reactions were detected in all alloys. The reaction sensitivity varied with specimen absorbed energy. Large, macroreactions occurred on specimen shear lips, a region that has very high deformation and is exposed to striker pin-specimen friction. Small microreactions occurred over many areas of the specimen. The effects of the test variables (pressure, drop height, LOX, GOX) on the frequency of macro- and micro-reations are discussed. The energy for fracture is usually less than, or equal to, the energy for (oxygen) reaction.
Aluminum-Lithium Alloys: Mechanical Property and Composition Effects on Liquid Oxygen Compatibility
Authors: Tack WT , McNamara DK , Stoltzfus JM , Sircar S
Published: March 2009

A wide range of composition and temper variants of aluminum-lithium alloys were fabricated and subjected to an exaggerated liquid oxygen (LOX) impact test. In addition, each of the five alloys were evaluated using a promoted combustion test to determine the threshold pressure. Within the scope of this study, a close correlation was found between mechanical properties and LOX impact reaction frequency as defined by visual observation. Scanning Electron Microscopy was used to examine tested specimens. The mechanical property and impact sensitivity relationship, combined with failure analysis and reaction classifications, provide a means to determine the probable mechanisms for impact reactions. With regard to the promoted combustion test, aluminum-lithium alloys display a ten-fold increase in threshold pressure compared with conventional aluminum alloys. The probable mechanisms contributing to this advantage will be discussed.
Macro- and Microreactions in Mechanical-Impact Tests of Aluminum Alloys
Authors: Reed RP , McCowan CN , McColskey JD , Simon NJ
Published: March 2009

Open-cup and pressurized mechanical-impact tests have been conducted at the NASA White Sands Test Facility (WSTF) on selected tempers of Al-Li alloys (2090, 8090, WL049), and Al alloy 2219. Both liquid (LOX) and gaseous (GOX) oxygen environments were used and pressure and drop height (potential energy) were varied in each environment. Reactions were observed in all alloys and tempers on both sides of the specimens. Reaction sizes, morphologies, and locations were characterized using a magnifying glass (2X power), a light microscope (5 to 100X), and a scanning electron microscope (100 to 3000X). Photomicrographs of various types of macro- and microreactions are presented and discussed. The variety of sizes of reactions poses a serious problem for the definition of a reaction in standards documents for LOX and GOX mechanical-impact qualification testing. This dilemma is discussed.
The Relative Ignitability and Flammability of Lead-Tin Binary Alloys in Oxygen
Authors: Sircar S , Stoltzfus JM , Gunaji MV
Published: March 2009

The relative ignitability and flammability of pure lead (Pb), pure tin (Sn), and a series of binary Pb-Sn alloys in liquid and gaseous oxygen was studied. Resistance to ignition by mechanical impact in liquid oxygen was studied using the Standard Test Method for Compatibility of Materials with Liquid Oxygen (the ASTM D-2512 technique) with slight modifications. Flammability was studied using the NASA White Sands Test Facility's (WSTF) promoted combustion tester. There were no reactions in the mechanical impact test for pure Pb, pure Sn, Pb-98.5Sn, Pb-10Sn, Pb-5Sn, and Pb-2Sn. However, the other alloys exhibited between two and six reactions out of twenty impacts. In the promoted combustion test, the threshold oxygen pressure required for complete consumption of a pure Pb sample was about 5 MPa (700 psig), whereas, for all the binary alloys tested and for pure Sn, the value was about 2 MPa (300 psig). The results obtained from the tests have been correlated with the Pb-Sn equilibrium binary phase diagram, the thermophysical properties of Pb-Sn binary alloys, and the thermodynamic properties of the oxides of both Pb and Sn. The chemical segregation characteristics of Pb and Sn in the presence of pure oxygen at high temperatures have been used to explain the results of the promoted combustion tests.
Temperature Increases in Aluminum Alloys During Mechanical-Impact Tests for Oxygen Compatibility
Authors: Simon NJ , Reed RP
Published: March 2009

In mechanical-impact testing of Al-Li alloys and Al alloy 2219 for oxygen compatibility, specimens absorb a significant amount of energy in a short time. The absorbed energy is sufficient to crack and, in many cases, produce large fractures (splits) in the specimens. The high strain rate from impact results in the formation of adiabatic shear bands under adiabatic conditions in the deformed areas. Large local temperature increases in the specimens occur during deformation, leading to localized melting.

Estimates of temperature increases assuming macroscopic homogeneous deformation during impact are presented. Characteristic times to propagate a thermal transient and to complete the mechanical deformation process are estimated. The difference between the alloy systems in this characteristic time to propagate a thermal disturbance offers a possible explanation of the differences in sizes and frequencies of reactions observed in Al alloy 2219, compared to the Al-Li alloys.
Assessing LOX Compatibility for Aluminum-Lithium Alloys
Authors: Nguyen BK , Pham BT
Published: March 2009

High strength lithium bearing aluminum alloys offer a significant cost saving potential for application to advanced launch and space vehicles. Three well developed alloys, Al-Li 2090, Al-Li 8090, and Weldalite 049, were evaluated for potential application to the large liquid oxygen and hydrogen tanks for the Advanced Launch System. A series of oxygen compatibility tests evaluation was conducted which included the mechanical impact test in liquid and gaseous oxygen, as per NASA 8060.1B, and the promoted combustion test in pressurized gaseous oxygen. Test results indicated that these alloys were in the same fire hazard category as the Aluminum 2219 currently being used in the external propellant tank of the US Space Shuttles. The test results also highlighted a need for changing the current mechanical impact test standards.
Is “Lox Clean” Enough?
Authors: Bryan CJ , Carman WR , Schehl TA , Underhill LD
Published: March 2009

Inspection of a new liquid oxygen (LOX) component revealed that it was not visibly clean. A sampling procedure was developed to sample the contaminant for chemical analysis, the composition of the contaminant was determined, and the component was cleaned. Finally, an assessment is made of the hazards of using commercially available “LOX CLEAN” cloths, gloves, wipes, etc. The need for standards for “LOX CLEAN” are addressed and the contamination potential to optical systems and critical electronic components is noted.
Special Construction Features of Centrifugal Compressors for Oxygen Service
Authors: Boddenberg K , Waldmann J
Published: March 2009

Due to the risk, of fire, oxygen compressors are distinctly different,from machines for other gases. Consequently, it must be ensured through active and passive measures during construction, selection of material, manufacture, cleaning, erection, commissioning and quality assurance that any danger is excluded. The way in which a compressor is depressurized in an emergency and use of a fire wall ensure in the most unfavorable case, that damage to the facility and the hazard for the surrounding area are kept to a minimum.
The History of Pavement Management in the Federal Highway Administration
Authors: Nostrand WA
Published: March 2009

The paper begins with the results of the authors research into the beginnings of pavement management (PM) and pavement management systems (PMS) in the Federal Highway Administration (FHWA). It continues on through its continued emphasis over the years culminating in the establishment of the Pavement Divisions issuance of a Pavement Policy in January 1989, which includes a mandate that all State highway agencies (SHA) must develop and put into operation a comprehensive PMS within 4 years of the date of issuance of that policy.

The discussion traces PM in the FHWA as it relates to FHWA's program manual (FHPM) and other directives that relate directly to the required activities in SHAs as a condition to receiving Federal-aid. While there have not been many specific mandates to SHAs until this recent one, the FHWA does develop emphasis areas and promote new innovations to the highway community from time-to-time, so it is interesting to relate those initiatives to see how the present requirement came about.

In 1986, the FHWA reorganized to create a Pavement Division. Prior to that there was a Pavement Design Branch consisting of seven people that was part of the Design Division. Today the Pavement Division has 22 people and includes a Pavement Management Branch, which is an indication of the emphasis being placed on pavements and in particularly PMSs.

The FHWA presented an introductory PM training course for State and Federal engineers a considerable number of years ago. There was also a training course for cities and counties labeled “Road Surface Management for local Governments,” which was presented over 30 times and is the fore-runner of an updated course by the same name being offered today. There were several directives regarding the use of PMS which preceded the first FHPM on the subject. Now the FHWA, in cooperation with the Transportation Research Board (TRB) and the American Association of State Highway and Transportation Officials, (AASHTO) is offering an advanced course in PMSs for practitioners.

This paper traces the history, emphasis, pertaining directives, training, and organization with regard to PMS. It concludes with an insight to the future of PMS in FHWA and SHAs.
Pavement Management Systems — State of the Art
Authors: Saraswatula SR , Amirkhanian SN
Published: March 2009

The condition of the highway network in the United States is deteriorating rapidly. Maintenance and rehabilitation are becoming increasingly important. With an approximately 4 million mile highway network in place, and limited funds available for its maintenance, pavement management is assuming a significant role in the activities of America's highway agencies. This paper traces the history, development, and implementation of pavement management systems (PMS) through the past two decades. The results of a survey assessing the impact of the FHWA ruling requiring all state agencies to implement PMS by 1993 are presented. Applications for geographic information systems, knowledge based expert systems, and voice recognition systems in pavement management are discussed.
Addressing Institutional Barriers to Implementing a PMS
Authors: Smith RE
Published: March 2009

Pavement management systems (PMS) are not being adopted and implemented at the rate expected. Many factors reducing the implementation can be attributed to barriers related to institutional issues. Diffusion of innovation studies help describe these barriers. They can also be used to help develop methods to remove or bypass the barriers.
Standard Engineering Principles in PMS Applications
Authors: Ullidtz P , Stubstad RN
Published: March 2009

An essential element of any Pavement Management System (PMS) is its ability to correctly predict the future “condition” of pavements. When a new PMS is introduced to a highway agency, the likelihood of successful implementation and acceptance is strongly dependent upon how well future pavement condition, as predicted by the system, agrees with local engineering knowledge of those pavements. Highway engineers still play an important role in the implementation of a PMS. Modeling pavement performance is extremely complicated, and no PMS can consider more than a few of the parameters involved, and then only in a highly simplified manner, whether they be analytical or “expert” system techniques. In order to improve the objective engineering performance and avoid rejection of the system, it is suggested that the following capabilities should be included in any PMS: ● A PMS must be capable of predicting structural as well as functional deterioration. Materials in the pavement layers, and their degradation under the effects of time and loading, are of primary concern to those highway engineers responsible for the maintenance and performance of the pavement network. A system that empirically predicts “only” the future ride quality or user costs ignores one of the main engineering considerations, and may be rejected as being too subjective or “political”. Currently accepted performance prediction techniques are usually applied at the project level for design purposes. At the network level, their application becomes somewhat more difficult, but now these difficulties can be dealt with. ● A method must be provided which uses predictive models tied to historical data as it becomes available in the specific PMS database, and for modifying these models so that the engineers' knowledge of local materials, environmental effects, construction and maintenance practices, etc., can easily be incorporated in the modeling procedure. In other words, predictive models based on sound engineering principles can be calibrated for a specific PMS application using historical data from the system itself. “Modeling” pavement performance by extrapolating future condition from historical data is a technically unacceptable simplification, however, because the effects of material degradation, maintenance, or rehabilitation measures cannot be considered. The engineering techniques for dealing with this new approach already exist and are applicable to a system-wide analysis. Statistical use of historical data (often of dubious quality) appears to be a poor substitute for engineering skill and the use of presently available analytical tools.
Criteria for Evaluating Pavement Management Systems
Authors: Paterson WDO , Robinson R
Published: March 2009

Agencies wishing to procure an available pavement management system appropriate to their institution and circumstances are faced with a complex series of tradeoffs between many system features and the probable need for system modifications. A set of generic criteria is presented for use in evaluating the completeness and appropriateness of a system, and in ranking alternative systems when a quantitative evaluation is desired. The fifteen criteria cover system completeness, the user interface, the analytical model, and data collection and management. The scope covers strategic planning, network programming and budgeting, project design and implementation (construction) monitoring. A supporting checklist of over 100 detailed criteria is provided for help in reaching a quantitative assessment.
History and Implementation of Pavement Management in Kentucky
Authors: Allen DL , Rizenbergs RL , Sharpe GW
Published: March 2009

Initiation of a pavement management system in Kentucky occurred in the early 1980's. Since that time, the system has continued to evolve into a more complex and extensive working system. This paper documents current pavement management practices and identifies future needs. The current organizational plan of the pavement management system is described. The goals, functions, and major tasks of the Pavement Management Branch of the Kentucky Transportation Cabinet are listed. A brief description of some of the pavement evaluation procedures currently being used is also included. It is concluded that Kentucky's pavement management system is well advanced, particularly in the area of pavement evaluation and condition assessment.
Implementation Process Used in the Development of the Illinois Pavement Feedback System
Authors: Hall JP
Published: March 2009

Addressing the Institutional issues is one of the most important criteria in implementing an effective pavement management process in a state highway agency. This paper describes the organizational issues involved in the implementation effort including resistance to change, not-invented-here syndrome, misdirected outputs, turf issues, and the long time frame required for development. The implementation process used by the Illinois Department of Transportation is outlined including the use of committees and the long-term planning of development and implementation phases. Finally, the paper portrays general concepts which can be utilized to effect implementation in state highway agencies.
Implementation of a Pavement Management System for Indiana Airports — A Case History
Authors: Eckrose RA , Reynolds WG
Published: March 2009

The development of a Statewide Pavement Management System for Indiana airports was a multi-year project. The project has been carefully designed to ensure workability and to capitalize on changes in the state of the art in Pavement Management. The first year was an exploration of the Pavement Condition Index (PCI) inspection procedure. The first twenty eight airports were inspected in 1985, using the PCI procedures as outlined by the Federal Aviation Administration. This first step was unique in that it was the first statewide inspection conducted with the financial assistance of the FAA.

The second phase of the project, covering some twenty airports was conducted in 1986. At this stage, the basic inspection was supplemented with computer software which allowed the state to construct and manipulate Capital Improvement Programs for the pavement systems over a six year planning window.

The project continued in 1989–90 with additional updated PCI inspections at twenty one airports and with the installation of a complete Airport Pavement Management System (APMS) on state computers, which allows the state to update and maintain the system on its own. It also permits the state to conduct in-depth analysis of pavement systems and individual features including forecasts of condition and analysis of maintenance and/or rehabilitation alternatives.

After several years of development and improvement, the State of Indiana now has, in place, a comprehensive APMS which provides a significant decision making tool for planning of needs and capital expenditures for pavement systems for a ten year period.
Performance Indications from Army Airfield Pavement Management Program
Authors: Hall JW , Grau RW , Grogan WP , Hachiya Y
Published: March 2009

Data from a pavement evaluation program implemented on U. S. Army airfields are presented to indicate both the predominant surface distresses and the structural adequacy of the pavements. Comparison of deterioration rates in terms of the pavement condition index (PCI) is presented by relating PCI to service age. An assessment of construction quality of both PCC and AC surfaces is made by comparing tests on core samples to design requirements. The method for selection of alternatives for routine maintenance, major maintenance, rehabilitation, and reconstruction is presented.
Data Collection in Belgium and Their Use in the Maintenance Planning System
Authors: Heleven LJE , Dirckx P
Published: March 2009

A maintenance planning system is under development in Belgium. It uses the longitudinal evenness, the rut depth, the skid resistance and the bearing capacity as road qualities. Visual inspection is also carried out. The different prediction models are given, and all the individual intervention threshold values. The overlay design is based on the deflection measurement and the damage factor, derived from the visual inspection.
Standardization of Distress Measurements for the Network-Level Pavement Management System
Authors: Lee H
Published: March 2009

Pavement distress information is one of the most important inputs to a pavement management system. Each state developed its own procedure to collect pavement distress data, which resulted in the lack of standardization of distress measurements for pavement management. The full standardization of the pavement management system cannot be achieved without standardizing its input. In addition, there always exists an inconsistency among different raters when they are conducting visual distress surveys. The inconsistency among the raters seems to be a problem for most state highway agencies. The automated image processing technology could help develop a standard crack measure. This paper presents a standard crack density method using video images of pavement surfaces, which can be easily adopted by all fifty states for their network-level pavement management systems. The standard crack density can be automatically computed by dividing the number of crack pixels by the number of total pixels of the pavement surface using the existing image processing technique. The standard crack density is an objective, consistent, and repeatable measure of cracks.
Development of Optimal Long-Term Network Strategies Using Remaining Service Life
Authors: Kuo W-H , Novak EC , Baladi GY
Published: March 2009

State Highway Agencies (SHA) develop Maintenance, Rehabilitation and Reconstruction (MR&R) programs every year. These programs may be optimal under some criteria. However, the impacts of these programs on the long-term network condition levels and funding needs are generally unknown. This is because the element of controlling long-term network condition and funding levels is not incorporated into the program development process. This paper presents a Strategy Analysis that uses a Remaining Service Life (RSL) concept to estimate long-term network conditions and funding needs. The characteristics of the strategy analysis are then used to develop optimal long-term network strategies. The procedures for incorporating optimal long-term network strategies into a program development process to develop optimal MR&R programs and at the same time control future network condition and funding levels are also presented.

This strategy analysis method is based on RSL which is obtained from pavement performance curves of condition measurements such as distress index, PSR, ride quality, rut depth,…, etc. It is a generic method because it can be used by any SHA that has established pavement performance curves. The linkage between project and network levels for developing MR&R programs are also discussed.
The Determination of SBS, EVA and APP Polymers in Modified Bitumens
Authors: Choquet FS , Ista EJ
Published: March 2009

The use of polymer-modified bitumens has gained importance in road construction over the past few years. The fields of application are relatively varied and include waterproofing sheets as well as binders for surface dressings, porous asphalt, mastic asphalt and asphalt concrete. Those polymers mainly used are styrene-butadiene-styrene SBS copolymers, ethylene-vinyl acetate EVA and atactic polypropylene APP. In addition to adequate and constant quality of the modified binder, the user is entitled to require a qualitative identification and quantitative determination of the polymer incorporated in a bitumen. Infrared absorption spectroscopy is suggested as an appropriate technique for identifying and determining polymer components in the case of SBS and EVA. Two techniques of preparing samples for measurement and two methods of quantitative interpretation are described. As for APP, its quantitative determination is based on selective solubility in different solvents and infrared spectroscopy.
Influence of the Rheological Properties of Modified Asphalt Binders on the Load Deformation Characteristics of the Binder-Aggregate Mixtures
Authors: Tayebali AA , Goodrich JL , Sousa JB , Monismith CL
Published: March 2009

While fatigue distress is still of major concern relative to the performance of asphalt pavements, permanent deformation in the form of rutting is assuming more significance for heavy duty highway pavements because of increased number of repetitions of heavy axle loads and increased tire pressures resulting from the use of radial tires (as compared to bias ply tires). In recent years, asphalt modifiers have found increasing use in mitigating excessive permanent deformation in the asphalt concrete pavements. However, questions arise as to what methodology should be used in comparing modifiers and in selecting the amount of modifier which should be used for a particular application.

This paper presents results of a study in which the applicability of dynamic testing is evaluated for assessing rutting potential for mixtures containing modified asphalt binders. Particular emphasis is placed on the rheologic properties of the modified asphalt binders and the binder-aggregate mixtures. Watsonville granite and an AR-2000 California Valley asphalt, and the same asphalt modified with Microfil 8 and K4460 modifiers were used in this investigation.

While the rheologic properties of modified binders may suggest improved performance over the same asphalt in the unmodified state, it is still necessary to define the performance characteristics of the mixture since the aggregate exerts a significant influence on mixture performance.

Mixture stiffness by itself does not appear to provide a measure for assessing the propensity for rutting in mixtures containing modified asphalt binders. Accumulated plastic deformation obtained under dynamic loading seems to represent better, the potential for rutting in mixtures containing modified asphalt binders. These dynamic tests provide results which are sensitive to asphalt type, temperature, degree of compaction and binder content.
Viscosity Measurements of Polymer Modified Asphalts
Authors: Schwager BP
Published: March 2009

Five samples of polymer modified asphalt were tested for viscosity at 60°C (140°F) using ASTM Test Method D2171 (Viscosity of Asphalts by Vacuum Capillary Viscometer). The samples were obtained from four different suppliers, and the polymers used included SB (styrene-butadiene), SBR (styrene-butadiene rubber latex), SBS (styrene-butadiene-styrene block copolymer), Neoprene and EVA (ethylene-vinyl acetate copolymer). Ten labs participated in the study. Each lab was asked to measure the viscosity of each sample using straight walled viscometers (either Asphalt Institute or modified Koppers type) and using Cannon-Manning viscometers. Analysis of the results shows that straight walled viscometers should be used for determining the viscosity of polymer modified asphalts. Four of the five samples were found to have Newtonian behavior at this temperature.
SBS-Modified Asphalts for Surface Dressing — A Comparison Between Hot-Applied and Emulsified Binders
Authors: Serfass J-P , Joly A , Samanos J
Published: March 2009

Styrene-butadiene-styrene addition improves the properties of asphalt in surface dressing: the thermal susceptibility is reduced and the binder cohesion increased, hence better resistance to bleeding and to aggregate dislodgement. The characteristics of hot-applied and emulsified SBS-modified binders are compared through series of laboratory tests: rheological properties, cohesion, tensile strength, toughness and tenacity. Application problems and field performance are globally examined. Hot-applied SBS-modified binders encounter viscosity and adhesion problems. They require a high amount of diluent, that may soften the support and cause aggregate embedment. Their SBS-content must be limited. Emulsified SBS-modified asphalts show excellent adhesion to all types of aggregate. They require very small amounts of diluent. High SBS contents can be employed. Their main drawback is slow setting time.