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Effective conventional manufacturing techniques are required to integrate the nanomaterial configurations into material systems at a larger component and structural level to obtain the enhanced benefits offered by the material configurations at the nano length scale. A low cost manufacturing process based on vacuum assisted resin transfer molding (VARTM) is demonstrated for the effective processing of fiber composite laminates using modified epoxy resin systems dispersed with nano and sub-micron alumina oxide particles. The effect of alumina oxide particles on the thermo physical properties (glass transition temperature, etc), are studied via differential scanning calorimetry and thermal gravimetric analysis. Higher glass transition temperatures with the alumina oxide and other nano particulate systems provide an opportunity to use conventional resin systems in high temperature applications. Ultrasonic mixing is employed to uniformly disperse the particles into an epoxy resin system. The flow characteristics of the modified resin system are not significantly different than the neat resin system and allowed the use of traditional VARTM processes successfully. The details of the resin modification and current studies on particulate modification for better interfacial bond are discussed in this paper. Wear performance for reinforced plastics are also investigated in this paper. Composite laminates with S2 glass and modified resins are fabricated. The mechanical behavior of the fabricated composite laminates with the neat and modified resin system using different sized and loading of alumina oxide particles are presented and discussed.Copyright © 2005 by ASME

Advances in conventional tape laminates and textile composites provide aircraft manufacturers important technology, but the industry lacks the confidence to use these composites to manufacture wing and fuselage structures due to high cost and low damage tolerance. In order to overcome the high cost and to improve the damage tolerance of composites, researchers have developed new through-the-thickness reinforcement techniques, such as stitching through the thickness. This reinforcement technique can be used to join the skin, stiffeners, ribs and spars to form an integral structure. The structures are typically more damage tolerant, contain fewer fasteners and are less expensive to manufacture than conventional composite or metallic structures. Furthermore, stitching reduces the manufacturing time and labor compared to drilling holes for fasteners, and may eliminate the problems of fatigue and/or corrosion from galvanic reactions with metal fasteners. Woven composites with through the thickness reinforcements such as stitching have good properties not only in mutually orthogonal directions but also in the transverse direction and more balanced properties than traditional tape laminates. They are also expected to have better fatigue and impact resistance due to the interlacing. Another benefit is reduced manufacturing cost by reducing part count. Because of these potential benefits, these composites are being considered for various applications including primary/secondary components for aerospace structures. The objective of this effort is to develop experimental tools for comparing the performance of these composites reinforced by stitching to unstitched composites. Identification of damage mechanisms and forces available to grow damage is essential for identifying the primary parameters that determine performance. Accurate determination of the driving forces will require extensive manufacturing and experimentation. However, once the reinforcement techniques are well understood, it is anticipated that simplified experiments can be developed that could be used routinely by designers to evaluate the effects of the reinforcements on damage tolerance. This paper specifically addresses the performance evaluation of stitched low cost manufactured composites subjected to static loading. Static tension and compression testing was conducted to determine the Ultimate Tensile and Compressive Strengths, Young’s Moduli and Poisson’s Ratio. Two different stitch patterns or stitch densities were used for comparison. The first density was five rows of stitching per inch of width, with eight stitches per inch over the entire length. The second density was three rows of stitching per inch of width, with four stitches per inch over the entire length.Copyright © 2005 by ASME

Braided composites have more balanced properties than traditional tape laminates, and have potentially better fatigue and impact resistance due to the interlacing. The natural conformability of biaxial braided tubes makes it the ideal preform for three-dimensional complex components. Braid tube fits on complex components with ease just like pulling socks on feet. Thus cutting, stitching, or manipulation of fiber placement is not needed, as in the use of woven fabrics. Biaxial braided composites find applications in aerospace, automotive, construction, medical, and recreational industry. Some of the products are automobile cross beams, lamp and utility poles, prosthetic limbs, hockey sticks, baseball bats, and bicycle components. Vacuum assisted resin transfer molding (VARTM) is a low-cost manufacturing process with the capability of manufacturing complex parts with higher fiber volume fractions than those from hand lay-up. To utilize the braided composites to the fullest advantage (and hence to avoid underutilization), it is necessary to understand their behavior under flexural, impact, and fatigue loading. Flexural loading is dominant in the above-mentioned applications of braided composites. This research addresses the effect of braid angle on flexural behavior and failure mechanisms of biaxial braided composites manufactured using VARTM.Copyright © 2005 by ASME

Braided composites have good properties in mutually orthogonal directions, more balanced properties than traditional tape laminates, and have potentially better fatigue and impact resistance due to the interlacing. Another benefit is reduced manufacturing cost by reducing part count. Because of these potential benefits braided composites are being considered for various applications ranging from primary/secondary structures for aerospace structures [1]. These material systems are gaining popularity, in particular for the small business jets, where FAA requires take off weights of 12,500 lb. or less. The new process, Vacuum Assisted Resin Transfer Molding (VARTM), is low cost, affordable and suitable for high volume manufacturing environment. Recently the aircraft industry has been successful in manufacturing wing flaps, using carbon fiber braids and epoxy resin and the VARTM process. To utilize these VARTM manufactured braided materials to the fullest advantage (and hence to avoid underutilization), it is necessary to understand their behavior under different loading and environmental conditions. This will reduce uncertainty and hence reduce the factor of safety in the design. It is well known fact that the strength of the composite structure reduces because of discontinuities and abrupt change in the cross-section. Accurate knowledge of strength and failure mechanism of notched and unnotched composites is very important for design of composite structures. This research addresses the behavior of notched braided composites under static tensile loading.Copyright © 2004 by ASME

Braided composites have good properties in mutually orthogonal directions; more balanced properties than unidirectional laminates and have better impact resistance. These composites are being considered as a primary load carrying components in place of conventional laminated composites. They are being manufactured by using new process such as Vacuum Assisted Resin Transfer Molding (VARTM). This new process is a low cost, affordable and suitable for high volume manufacturing environment. In VARTM process, the flow of resin occurs in-plane as well as in the transverse directions to the preform. The permeability of the preform, fiber architecture and fabric crimp has an influence on the wetting of the fabric. This paper addresses a detailed study of VARTM manufactured 2x2 biaxial braided composites. These composites are fabricated using AS4 carbon fibers and vinyl ester resin system components. These braided composites are being evaluated for structural applications. To assess the feasibility of this material manufactured through VARTM, it is very important to understand the tensile behavior of these composite materials. Numbers of tests are performed to evaluate the basic properties such as modulus, ultimate tensile strength, and Poisson's ratio of VARTM manufactured braided composites. This paper also presents, a finite element model for the 2 x 2 biaxial braided composites to predict the mechanical properties.

One of the driving forces for the increasing structural application of textile composites is the potential to tailor the material microstructure to meet specific thermomechanical requirements. In order to fully exploit this potential, thorough understanding of the effect of various factors on the behavior of the material is essential. This paper focuses on understanding the effect of braid angle and tow waviness on the effective moduli of 2x2 biaxial braided composites. To achieve this goal, full three-dimensional finite element micromechanics models were developed first. Then extensive parametric study was conducted for typical glass fiber/epoxy (S2/SC-15) and carbon fiber/ epoxy (AS4/411-350) material systems. The effects of tow waviness and braid angle on the effective engineering properties were determined for a wide range of braid angles and waviness ratios. Equivalent laminated materials with angle plies and a resin layer were also used to produce reference values for comparison. The results are presented and discussed. The transverse properties of the 2x2 biaxial braids are most sensitive to the change of braid angle and waviness ratio. The in- plane properties of the braid can be well predicted by the classical laminate theory for a range of small waviness for the carbon fiber/epoxy material.

Future aircraft technology enhancements (FATE) develop revolutionary technologies that will become the foundation for the next generation of war fighters. The structures thrust of the Air Vehicles Directorate further supports the Air Force need toward a composite affordability initiative (CAI). Affordability and survivability are keys to air and space vehicles for higher performance, longer life, and cost effectiveness. In the current research project, issues of CAI were addressed. The technical work carried out is presented in three volumes. Volume 1 addresses the performance of carbon/epoxy composites that were manufactured using affordable vacuum assisted infusion molding (VARIM) process. Panels made of stitched/unstitched plain, satin, and twill weave of different thicknesses were subjected to high velocity impact loading using a gas-gun facility. Damage modes were evaluated through ultrasonic nondestructive evaluation (NDE). Effect of projectile geometry was studied. In all of the laminates, the damage was localized and was dominated by penetration rather than delamination. This resulted in laminates with lower damage size with increased residual mechanical properties as compared to the unidirectional laminates that are used in the current aircraft structures.

Experimental investigations carried out on affordable woven carbon/epoxy laminates under low-velocity impact loading are reported in this volume. Stitched and unstitched carbon/epoxy laminates were fabricated using plain and satin weave fabric with SC-15 epoxy resin system. Two orthogonal stitch spacing: 12.7- and 15.4-mm were used. Four-inch square samples were subjected to low-velocity impact loading at energy ranging from 5-40 J. Results of the study indicated that the damage due to low-velocity impact loading reduced considerably due to stitching. Of the two weave types, satin weave laminates carried higher impact loads compared to plain weave laminates due to relatively straighter fiber architecture. In another study, effects of laminate thickness and samples size on the upper and lower-bound energy level were established. To establish damage tolerance of woven fabric composites, post impact studies were carried out which included static compression and fatigue tests. Post fatigue tension tests were carried out to determine the reduction in stiffness. Though most of the laminates sustained 100,000 fatigue cycles, there was a sharp decrease in the stiffness with increasing drop height.

Braided composites have good properties in mutually orthogonal directions, more balanced properties than traditional tape laminates, and have potentially better fatigue and impact resistance due to the interlacing. Another benefit is reduced manufacturing cost by reducing part count. Because of these potential benefits braided composites are being considered for various applications ranging from primary/secondary structures for aerospace structures [1]. These material systems are gaining popularity, in particular for the small business jets, where FAA requires taken off weights of 12,500 lb. or less. The new process, Vacuum Assisted Resin Transfer Molding (VARTM), is low cost, affordable and suitable for high volume manufacturing environment. Recently the aircraft industry has been successful in maufacturing wing flaps, using carbon fiber braids and epoxy resin and the VARTM process. To utilize these VARTM manufactured braided materials to the fullest advantage (and hence to avoid underutilization), it is necessary to understand their behavior under different loading and environmental conditions. This will reduce uncertainty and hence reduce the factor of safety in the design. Any typical structural member made of composite material is subjected to different types of loading such as static, impact, cyclic causing fatigue, and environmental effects such as change in temperature and exposure to moisture and other corrosives. It is well known that cyclic loading reduces the strength of a material and its useful life or, the fatigue strength of a material is lower than its static strength. This is true of all materials—metals, plastics, composite materials, etc. In structural applications, fatigue loading is unavoidable especially in aerospace and ground transportation applications. This research addresses the tensiontension fatigue behavior of biaxial braided composites.Copyright © 2003 by ASME

Woven textile composites are replacing multidirectional laminates primarily because of their properties in mutually orthogonal directions as well as more balanced properties and better impact resistance. One of the affordable low cost woven composites is manufactured by using graphite fibers and SC-15 epoxy resin through resin infusion or resin transfer molding processes. Before these composites can be used in aircraft as primary load carrying structures, it is essential to investigate behavior of these laminates subjected to low velocity impact loading. This research addresses the progressive damage and deformation mechanics of thin and thick woven composites subjected to low velocity impact loading.

Radicular cyst is the most common inflammatory odontogenic cystic lesion of the jaws. It usually originates as sequel to a periapical inflammatory process, following chemical, physical or bacterial injury. Due to its chronic etiology, the cyst usually appears in the later stages of life. It has a male sex predilection, with the maxillary anterior region as the most common site of involvement. This article describes an unusual case of a large radicular cyst in the posterior maxilla along with its management and follow-up.

The calcifying epithelial odontogenic cyst (CEOC) is a developmental odontogenic cyst, which was first categorized as a distinct entity by Gorlin in 1962. It is an unusual and unique lesion, which may show characteristics of both a solid neoplasm and a cyst. It usually occurs as an intra-osseous lesion but may occasionally occur as an extra-osseous or peripheral variant. It shows a nearly equal distribution between the maxilla and mandible and is commonly seen anterior to the first molar. The clinical and radiographic features of this lesion are not pathognomonic, and it is characterized by its histological diversity, with the most characteristic feature being the presence of a variable number of ghost cells within the epithelial component. Treatment is conservative with surgical enucleation, and recurrences are rare. This report describes a case of CEOC in association with an impacted mandibular first premolar, which was diagnosed in a 13-year-old female patient, along with a review of the literature.

Osteomas are benign osseous neoplasms that show continuous but slow growth and are characterized by the proliferation of compact and/or cancellous bone. The exact cause is unknown, and they are usually considered to represent hamartomas or reactive lesions secondary to low-grade inflammation. They can be classified into central, peripheral or extra-skeletal types. Peripheral osteomas occur most frequently in the frontal and ethmoid sinuses, and jaw involvement is rare. They are usually asymptomatic and may be discovered during routine clinical and radiographic examination. Radiographically, peripheral osteomas appear as oval radiopaque well-circumscribed masses attached to the cortex by a broad base or a pedicle. This article describes a case of a peripheral osteoma of the right angle of the mandible in a 20-year-old male along with a literature review.

Changes related to chronological age are seen in both hard and soft tissue. A number of methods for age estimation have been proposed which can be classified in four categories, namely, clinical, radiological, histological and chemical analysis. In forensic odontology, age estimation based on tooth development is universally accepted method. The panoramic radiographs of 500 healthy Goan, Indian children (250 boys and 250 girls) aged between 4 and 22.1 years were selected. Modified Demirjian's method (1973/2004), Acharya AB formula (2011), Dr Ajit D. Dinkar (1984) regression equation, Foti and coworkers (2003) formula (clinical and radiological) were applied for estimation of age. The result of our study has shown that Dr Ajit D. Dinkar method is more accurate followed by Acharya Indian-specific formula. Furthermore, in this study by applying all these methods to one regional population, we have attempted to present dental age estimation methodology best suited for the Goan Indian population.

The purpose of this paper is to investigate the piston temperature and stress distribution resulting from varying coating thicknesses of Partially Stabilized Zirconia (PSZ) thermal barrier coatings for the performance in diesel engine applications. This analysis is based on the premise that coating thickness affects the heat transfer and temperature distribution in the piston. A gas dynamic engine cycle simulation code was used to obtain thermal boundary conditions on the piston then, a 2-D axisymmetric Finite Element Analysis (FEA) using ANSYS was performed to evaluate the temperature and stress distributions in the piston as a function of coating thickness. Coating thicknesses studied include 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, and 2.0mm. The results indicate increased piston surface temperature with increasing coating thickness. The maximum stress on the coated piston surface was high while the substrate stress was less than the coating yield stress for all coating thicknesses. Further, the analysis showed that the interface stress at all coated conditions is low enough such that no separation of the coating is expected. The FEA results suggest an optimum coating thickness of 0.1 to 1.5 mm for diesel engine application to avoid unduly high stress in the ceramic.

Woven composites have good properties in mutually orthogonal directions, more balanced properties than unidirectional laminates and have better impact resistance. The use of these composites for primary structural applications in place of conventional laminated composites has been increased considerably in the recent years. They are being manufactured by using new processes such as Resin Infusion (VARIM) and Resin Transfer Molding (RTM). These new processes are low cost, affordable and suitable for high volume manufacturing environment. One of the popular plain woven composites is fabricated using S2-Glass and SC-15 resin system components by using Resin Infusion (VARIM) process. These woven composites are being evaluated for Integral Armor applications. These components are expected to be under fatigue loading. To assess the feasibility of this material manufactured through Resin Infusion (VARIM), it is very important to understand the fatigue behavior of these composite materials. The present study provides comparison of the performance evaluation of plain and twill woven composite material for Integral Armor applications. Tension-Compression (R = −1) fatigue experiments were performed. All the fatigue tests are performed at 1 Hz frequency. S-N diagram and stiffness degradation over the fatigue life of the specimens were obtained.

The present study provides the performance evaluation of 2 × 2 twill woven composite (S2-Glass and C-50 resin system) material for Integral Armor applications. The laminates were fabricated by using VARIM or RI (Vacuum Assisted Resin Infusion Molding). These components are expected to be under fatigue loading. Fatigue behavior of the unnotched and notched twill woven laminate is presented. Tension-Compression (R = −1) fatigue experiments were performed for both unnotched and notched panels. All the fatigue tests were performed at 1 Hz frequency. S-N diagram and stiffness degradation over the fatigue life of the specimen was obtained.

The present study provides the performance evaluation of 2x2 twill woven composite (S2-Glass and C-50 resin system) material for Integral Armor applications. The laminates were fabricated by two low cost processes: RTM (Resin Transfer Molding) and VARIM or RI (Vacuum Assisted Resin Infusion Molding). These components are expected to be under fatigue loading. Fatigue behavior of the twill woven laminate is presented. Tension-Compression (R = -1) fatigue experiments were performed for both RI and RTM panels. All the fatigue tests were performed at 1 Hz frequency. S-N diagram and stiffness degradation over the fatigue life of the specimen was obtained. The fatigue tests indicated that with the same volume of fibers and with more resin, RTM process improved the fatigue performance over RI process. The ratios of logarithm of fatigue life cycles of RTM and RI is almost constant. Therefore on the absolute scale the ratio keeps increasing at higher fatigue life or at lower fatigue loads. However, with the same volume of fibers and resin, the fatigue performance of RTM and RI processed panels were comparable. It was also observed that both RTM and RI exhibited classical three-stage degradation in stiffness.

Monolithic ceramics are highly sensitive to process and service related flaws, making them inherently brittle. Due to their low toughness, these materials fail catastrophically. Continuous fiber-reinforced composites usually provide a significant amount of toughness as well as avoid catastrophic failure. The interface between the fiber and the matrix can significantly affect the mechanical properties of the composite. A very strong interface yields brittle fracture as the crack propagates through the matrix and fiber. In contrast a very weak interface between the fiber and matrix is incapable of transferring the load from the matrix to the fiber and hence the properties of the fiber are not used effectively and the mechanical properties are similar to that of a porous material. Therefore the design and optimization of the interface properties are of vital importance for fabricating ceramic composites with superior mechanical performance. Before these coated ceramic composites can be used in primary structural applications, it is necessary to obtain the fundamental properties of these materials. This paper presents a study on the effects of fiber coating thickness and fiber volume fraction on the transverse mechanical properties of coated ceramic composites.

In this paper a systematic investigation was carried out on the microstructural evolution of a sintered Si3N4 ceramics associated with high temperature soaking in air. The soaking was conducted at 1275 °C for various periods of time, ranging from 16 to 40 hours. High resolution transmission electron microscopy (HRTEM) and conventional TEM were used to study the microstructures of the virgin (as received) and soaked samples. It was found that the Si3N4 ceramics has been severely attacked even inside the material, most probably by oxygen. The originally distinctly shaped Si3N4 grain boundaries and triple junctions became more rounded and the apparent volume fraction of the amorphous phases was increased due to high temperature thermal soaking. Studies on samples prepared with the electron transparent region deliberately located in various specific regions showed that in general the thickness of the amorphous grain boundary phase expanded due to soaking. The clear-cut atomic steps or the faceted Si3N4 grains along the grain boundaries were smeared out. All these changes could be explained on the basis of oxygen attacks through fast path diffusion of oxygen species along the grain boundary phase, surface diffusion in the micropores or even through volume diffusion in the Si3N4 grains along specific orientation. This may contribute to a better understanding of the high temperature behavior of this material in oxidizing atmosphere.

Woven composites have good properties in mutually orthogonal directions, more balanced properties than unidirectional laminates and have better impact resistance. The use of these composites for primary structural applications in place of conventional laminated composites has been increased considerably in the recent years. They are being manufactured by using new processes such as Resin Infusion (RI) and Resin Transfer Molding (RTM). These new processes are low cost, affordable and suitable for high volume manufacturing environment. One of the popular woven composites is fabricated using S2-Glass and C-50 resin system components by using Resin Infusion (RI) and Resin Transfer Molding (RTM) process. These woven composites are being evaluated for Integral Armor applications. These components are expected to be under fatigue loading. To assess the feasibility of this material manufactured through Resin Infusion (RI) and Resin Transfer Molding (RTM), it is very important to understand the fatigue behavior of these composite materials. In the first phase of the study the panels of this material were fabricated using Resin Infusion (RI) processing. Number of tests were performed to evaluate the basic properties such as modulus, ultimate tensile strength, and Poisson’s ratio of this woven composite. Tension-tension fatigue experiments with R ratio of 0.1 were conducted to generate two important curves to characterize the fatigue behavior of this material system: S-N diagram and stiffness degradation over the entire fatigue life of the specimens. All the fatigue tests were performed at 1 Hz frequency. To study the progressive damage of the textile composites under fatigue loading, one set of specimens was subjected to different number of fatigue cycles starting from 1 cycle to 300,000 cycles and was investigated for failure mechanism using optical microscopy and SEM.