Thermoplastic coating of carbon fibers

Using a continuous powder coating process, more than 1500 meters of T 300/LaRC-TPI prepreg were produced. Two different types of heating sections in the coating line, namely electrical resistance and convection heating, were utilized. These prepregs were used to fabricate unidirectional composites. During composite fabrication the cure time of the consolidation was varied, and composites samples were produced with and without vacuum. Under these specimens, the effects of the different heating sections and of the variation of the consolidation parameters on mechanical properties and void content were investigated. The void fractions of the various composites were determined from density measurements, and the mechanical properties were measured by tensile testing, short beam shear testing and dynamic mechanical analysis

Carbon fibers and method for producing same

Carbon fibers having a multi-lobal transverse cross-section are produced by extruding a carbonaceous anisotropic liquid precursor through a spinneret having a capillary with a multi-lobal cross-section, solidifying the extruded filament, rendering the filament infusible, and heating the filament in an inert environment at a temperature sufficient to substantially increase the tensile strength and modulus of elasticity of the filament

Immiscible fluid: Heat of fusion heat storage system

Both heat and mass transfer in direct contact aqueous crystallizing systems were studied as part of a program desig- ned to evaluate the feasibility of direct contact heat transfer in phase change storage using aqueous salt system. Major research areas, discussed include (1) crystal growth velocity study on selected salts; (2) selection of salt solutions; (3) selection of immiscible fluids; (4) studies of heat transfer and system geometry; and (5) system demonstration

Thermoplastic coating of carbon fibers

A continuous powder coating system was developed for coating carbon fiber with LaRC-TPI (Langley Research Center-Thermoplastic Polyimide), a high-temperature thermoplastic polymide invented by NASA-Langley. The coating line developed used a pneumatic fiber spreader to separate the individual fibers. The polymer was applied within a recirculating powder coating chamber then melted using a combination of direct electrical resistance and convective heating to make it adhere to the fiber tow. The tension and speed of the line were controlled with a dancer arm and an electrically driven fiber wind-up and wind-off. The effects of heating during the coating process on the flexibility of the prepreg produced were investigated. The uniformity with which the fiber tow could be coated with polymer also was examined. Composite specimens were fabricated from the prepreg and tested to determine optimum process conditions. The study showed that a very uniform and flexible prepeg with up to 50 percent by volume polymer could be produced with this powder coating system. The coating line minimized powder loss and produced prepeg in lengths of up to 300 m. The fiber spreading was found to have a major effect on the coating uniformity and flexibility. Though test results showed low composite tensile strengths, analysis of fracture surfaces under scanning electron microscope indicated that fiber/matrix adhesion was adequate

The National Center for Effective Schools: Extending Knowledge and Practice of School Improvement

The structure and the programs of school improvement must constantly be reassessed and extended to take into consideration new knowledge and new practices that can serve school improvement

Method for producing high strength, melt spun carbon fibers

Hollow carbon fibers and carbon fibers having a generally C-shaped transverse cross-sectional area are produced by extruding a carbonaceous anisotropic liquid precursor through a spinneret having a capillary with a generally C-shaped cross-sectional area, into a fiber filament, controlling the viscosity of the molten precursor, the pressure of the molten precursor and the linear take-up speed of the filament to yield a fiber filament having a cross-sectional area shaped substantially like the shape of the cross-sectional area of the capillary and further having a line-origin microstructure, rendering the filament infusible, heating the filament in an inert pre-carbonizing environment at a temperature in the range of 600.degree. C. to 1000.degree. C. for 1 to 5 minutes, and heating the filament in an inert carbonizing environment at a temperature in the range of 1550.degree. C. to 1600.degree. C. for 5 to 10 minutes, to substantially increase the tensile strength of the filament. The carbon fiber filament so produced has a line-origin microstructure in which the origin line is located and shaped substantially as a line which constitutes the line formed by uniformly collapsing the perimeter of the transverse cross-sectional area of the fiber filament upon itself. The carbon fiber filament has a tensile strength greater than 200 ksi and as high as the 700 to 800 ksi range, yet a modulus of elasticity on the order of 25-35 msi. The top to bottom outside diameter of the fiber\u27s transverse cross-sectional area is on the order of 30 to 50 microns, and the wall thicknesses are on the order of 8 to 15 microns

Process for coating carbon fibers with pitch and composites made therefrom

The present invention is directed to a process for coating carbon fibers with a pitch material. The process employs a pressurized air-comb for spreading a carbon fiber tow into individual carbon fiber filaments and providing the carbon fiber filaments in a spreaded tow to a powder deposition chamber. A pitch material is dried and finely ground and is then fed into the coating chamber at a point above the traveling spreaded carbon fiber tow. The pitch powder initially falls onto the fiber tow and begins forming a uniform coating around the individual carbon fibers. After falling past the point of the traveling carbon tow, the pitch powder is then recirculated back to the upper portion of the coating chamber and is entrained within a pitch powder cloud through which the threaded fiber tow travels. Fibers that are coated by such a method may be used to form carbon/carbon composites that exhibit high strength and excellent mechanical properties. The carbon fibers that are coated according to the present invention do not require the repeated multi-impregnation steps normally associated with carbon/carbon composite formation

High strength, melt spun carbon fibers and method for producing same

Hollow carbon fibers and carbon fibers having a generally C-shaped transverse cross-sectional area are produced by extruding a carbonaceous anisotropic liquid precursor through a spinneret having a capillary with a generally C-shaped cross-sectional area, into a fiber filament, controlling the viscosity of the molten precursor, the pressure of the molten precursor and the linear take-up speed of the filament to yield a fiber filament having a cross-sectional area shaped substantially like the shape of the cross-sectional area of the capillary and further having a line-origin microstructure, rendering the filament infusible, heating the filament in an inert pre-carbonizing environment at a temperature in the range of 600.degree. C. to 1000.degree. C. for 1 to 5 minutes, and heating the filament in an inert carbonizing environment at a temperature in the range of 1550.degree. C. to 1600.degree. C. for 5 to 10 minutes, to substantially increase the tensile strength of the filament. The carbon fiber filament so produced has a line-origin microstructure in which the origin line is located and shaped substantially as a line which constitutes the line formed by uniformly collapsing the perimeter of the transverse cross-sectional area of the fiber filament upon itself. The carbon fiber filament has a tensile strength greater than 200 ksi and as high as the 700 to 800 ksi range, yet a modulus of elasticity on the order of 25-35 msi. The top to bottom outside diameter of the fiber\u27s transverse cross-sectional area is on the order of 30 to 50 microns, and the wall thicknesses are on the order of 8 to 15 microns

Measuring Biodiversity and Extinction – Present and Past

How biodiversity is changing in our time represents a major concern for all organismal biologists. Anthropogenic changes to our planet are decreasing species diversity through the negative effects of pollution, habitat destruction, direct extirpation of species, and climate change. But major biotic changes – including those that have both increased and decreased species diversity – have happened before in Earth’s history. Biodiversity dynamics in past eras provide important context to understand ecological responses to current environmental change. The work of assessing biodiversity is woven into ecology, environmental science, conservation, paleontology, phylogenetics, evolutionary and developmental biology, and many other disciplines; yet, the absolute foundation of how we measure species diversity depends on taxonomy and systematics. The aspiration of this symposium, and complementary contributed talks, was to promote better understanding of our common goals and encourage future interdisciplinary discussion of biodiversity dynamics. The contributions in this collection of papers bring together a diverse group of speakers to confront several important themes. How can biologists best respond to the urgent need to identify and conserve diversity? How can we better communicate the nature of species across scientific disciplines? Where are the major gaps in knowledge about the diversity of living animal and plant groups, and what are the implications for understanding potential diversity loss? How can we effectively use the fossil record of past diversity and extinction to understand current biodiversity loss

Characterization of hybrid chondroitin/dermatan sulfate octasaccharide domains in human brain by ion mobility tandem mass spectrometry

We report here on the introduction of a rapid, highly sensitive and reliable approach in a single run, based on ion mobility separation (IMS), high resolution and tandem MS (MS/MS) by collision-induced dissociation (CID) for compositional and structural elucidation of neural chondroitin sulfate (CS) and dermatan sulfate (DS) domains, which implies the determination of the epimerization and the sulfation code of regular and irregular structures. By IMS MS and CID MS/MS, we were able to characterize in details CS/DS octasaccharides from brain obtained after CS/DS chain depolymerization by chondroitin B lyase and to detect sequences that were never found before in the octasaccharide domains of the investigated CS/DS brain fraction