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Optical Scanning (optical + scanning)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Identification of fiber misalignment in continuous fiber composites

POLYMER COMPOSITES, Issue 3 2003
S. C. Barwick
Misaligned fibers are invariably present in nominally unidirectional high-performance composites. Such misaligned fibers are known to affect key mechanical properties of the composite, such as the longitudinal compressive strength, longitudinal tensile modulus, fatigue endurance, shear strength, and delamination resistance (1). In this paper we present a method for the automated detection of large angle fiber misalignment (, > 40°) in continuous fiber-reinforced composite materials. The method relies on the application of a series of geometrical criteria based upon measurements routinely obtained during optical scanning of polished sample cross-sections. As such, the technique is ideal for the automated identification of highly misaligned fibers in large-area (, cm2) specimens that may contain several millions of individual fiber images. The criteria applied take into account the fact that prepared cross-sections of such materials contain many damaged fibers as a result of attrition during polishing. Data obtained from three pultruded unidirectional rods reinforced with continuous carbon filaments are used to illustrate the effectiveness of this method in identifying regions where large angle misalignment occurs. [source]

Preparation and characterization of ultrafine electrospun polyacrylonitrile fibers and their subsequent pyrolysis to carbon fibers

POLYMER INTERNATIONAL, Issue 8 2006
Juthawan Sutasinpromprae
Abstract The present contribution reports the fabrication and characterization of ultrafine polyacrylonitrile (PAN) fibers by electrospinning and further development of the as-spun PAN fibers into ultrafine carbon fibers. The effects of solution conditions (i.e., solution concentration, viscosity, conductivity, and surface tension) and process parameters (i.e., applied electrostatic field strength, emitting electrode polarity, nozzle diameter, and take-up speed of a rotating-drum collector) on morphological appearance and average diameter of the as-spun PAN fibers were investigated by optical scanning (OS) and scanning electron microscopy (SEM). The concentration, and hence the viscosity, of the spinning solutions significantly affected the morphology and diameters of the as-spun PAN fibers. The applied electrostatic field strength and nozzle diameter slightly affected the diameters of the as-spun fibers, while the emitting electrode polarity did not show any influence over the morphology and size of the as-spun fibers. Utilization of the rotating-drum collector enhanced the alignment of the as-spun fibers. Within the investigated concentration range, the average diameter of the fibers ranged between 80 and 725 nm. Finally, heat treatment of the as-spun fibers with their average diameter of about 450 nm was carried out at 230 and 1000 °C, respectively. Various characterization techniques revealed successful conversion into carbon fibers with an average diameter of about 250 nm. Copyright © 2006 Society of Chemical Industry [source]

Single Implants and Buccal Bone Grafts in the Anterior Maxilla: Measurements of Buccal Crestal Contours in a 6-Year Prospective Clinical Study

CLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 3 2005
Odont Dr/PhD, Torsten Jemt DDS
ABSTRACT Background: Patients provided with buccal bone grafts seem to lose a substantial part of the graft in the short term. Purpose: To measure long-term changes in buccal and proximal tissue volumes after local bone grafting and single implant treatment. Materials and Methods: Eight of 10 originally treated male patients were followed up for 6 years after treatment with buccal bone grafts in the central incisor region. After a healing time of 6 months, a two-stage implant surgery procedure was performed followed by single crown placement. Clinical photographs and impressions were taken prior to the surgical interventions and after crown placement and at first and fifth annual checkups. The photographs were analyzed with regard to papilla regeneration by means of a clinical papilla index. The models were used to measure the clinical length of teeth and tooth movements adjacent to the implants. Changes in buccal crest volume during the study period were measured by means of optical scanning of obtained study models. Results: Papillae volume increased significantly (p < .05) during the first year, thereafter showing a slow further increase during the 4 following years. Three of the patients (38%) presented small movements of their adjacent central incisor in a vertical or palatal direction of less than 1 mm during the follow-up period. All patients showed resorption during the first year after grafting (p < .01), in which three patients (38%) had lost basically all of increased volume at second surgery. After abutment or crown placement, all patients showed an increased volume (p < .01), followed by an average reduction during the first year, reaching a significant level in the apical part of the crest (p < .05). Thereafter, a relatively stable average situation was observed during the following 4 years, with individual variations, however. Conclusion: Local bone grafting seems to create sufficient bone volume for implant placement after 6 months, but individual variations in resorption pattern make the grafting procedure unpredictable for long-term prognosis. Instead, the abutment and the crown seem to play a more important role for building up and maintaining the buccal contour in the coronal part of the crest long term. [source]

Measurements of Buccal Tissue Volumes at Single-Implant Restorations after Local Bone Grafting in Maxillas: A 3-Year Clinical Prospective Study Case Series

CLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 2 2003
Odont PhD, Torsten Jemt LDS
ABSTRACT Purpose: The purpose of this study was to measure changes in buccal and proximal tissue volumes after local bone grafting and single-implant treatment. Materials and Methods: Ten patients were provided with buccal bone grafts 6 months prior to implant treatment in central upper incisor regions. Following a healing time of 6 months, abutments and single-implant crowns were installed and followed up for 2 years. Clinical photographs and impressions were taken prior to the surgical intervention as well as after crown placement and at first and second annual checkups. The photographs and study models were analyzed with regard to papilla regeneration and changes in buccal crest volume during the study period by means of a clinical papilla index and optical scanning of study models. Results: All bone grafts healed without problems. A significant reduction of the buccal crest volume (-50%, p <.01) was observed in the grafted area before abutment connection. However, a significant increase of tissue volume (+100%, p <.05) was noticed at the subsequent crown placement, followed by a second but slow reduction of the volume during the following 2 years of function. The interdental papillae increased significantly (p <.05) in volume during the first year, almost completely filling up the embrasure areas after 2 years. Conclusions: It may be concluded that local bone grafting seems to be a valuable protocol to create sufficient bone volume for implant placement. However, significant resorption of the graft may be present, which reduces the impact of grafting on the esthetic outcome. Instead, placement of the abutment cylinder and the crown seems to play a more important role for reestablishing the tissue volume at the implant-supported single crowns. [source]