Process for application of powder particles to filamentary materials

This invention is a process for the uniform application of polymer powder particles to a filamentary material in a continuous manner to form a uniform composite prepreg material. A tow of the filamentary material is fed under carefully controlled tension into a spreading unit, where it is spread pneumatically into an even band. The spread filamentary tow is then coated with polymer particles from a fluidized bed, after which the coated filamentary tow is fused before take-up on a package for subsequent utilization. This process produces a composite prepreg uniformly without imposing severe stress on the filamentary material, and without requiring long, high temperature residence times for the polymer

The Economics of Exporting North Dakota Beef to Asian Pacific Markets

International Relations/Trade,

An Analysis Of The Lyophilization Process Using A Sorption‐sublimation Model And Various Operational Policies

The freeze‐drying process is studied under various operational policies through the use of a sorption‐sublimation model. The operational policy that provides the shortest drying times keeps the pressure at its lowest value. The upper and lower heating plates are independently controlled so that the material constraints are encountered and held throughout the free water removal phase. Under certain conditions, and for the case of samples of small thickness, the sorbed water profiles may have segments whose bound water concentrations are higher than those at the start of the free water removal phase. It is shown that the criterion used in terminating the freeze‐drying process is of extreme importance, since it may lead to an undesirable sorbed water profile which may deteriorate the quality of the dried product. Copyright © 1985 American Institute of Chemical Engineer

Dry powder process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs

A process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs is provided. A plurality of polymer powder coated filamentary towpregs are provided. The towpregs are collimated so that each towpreg is parallel. A material is applied to each side of the towpreg to form a sandwich. The sandwich is heated to a temperature wherein the polymer flows and intimately contacts the filaments and pressure is repeatedly applied perpendicularly to the sandwich with a longitudinal oscillating action wherein the filaments move apart and the polymer wets the filaments forming a uni-tape prepreg. The uni-tape prepreg is subsequently cooled

Composite material impregnation unit

This memorandum presents an introduction to the NASA multi-purpose prepregging unit which is now installed and fully operational at the Langley Research Center in the Polymeric Materials Branch. A description of the various impregnation methods that are available to the prepregger are presented. Machine operating details and protocol are provided for its various modes of operation. These include, where appropriate, the related equations for predicting the desired prepreg specifications. Also, as the prepregger is modular in its construction, each individual section is described and discussed. Safety concerns are an important factor and a chapter has been included that highlights the major safety features. Initial experiences and observations for fiber impregnation are described. These first observations have given great insight into the areas of future work that need to be addressed. Future memorandums will focus on these individual processes and their related problems

A Dry Powder Process for Preparing Uni-Tape Prepreg from Polymer Powder Coated Filamentary Towpregs

A process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs is provided. A plurality of polymer powder coated filamentary towpregs are provided. The towpregs are collimated so that each towpreg is parallel. The sandwich is heated to a temperature wherein the polymer flows and intimately contacts the filaments and pressure is repeatedly applied perpendicularly to the sandwich with a longitudinal oscillating action wherein the filaments move apart and the polymer wets the filaments forming a uni-tape prepreg. The uni-tape prepreg is subsequently cooled

Beef Quality Assurance from Farm to Fork: Development of a Pilot Program in Farm to Table Food Safety

The goal of the project described here was to develop an interdisciplinary 3-day food safety training program. Course material for this program included content focused on food safety issues at the pre-harvest (farm, ranch, feedlot), post-harvest (slaughter and fabrication), and consumer (foodservice, retail, home) level. A pre-and post-test were given to each participant to assess the impact of this training program. Pre-test scores averaged 62%, while post-test scores averaged 87%. The 3-day interdisciplinary food safety course was effective at increasing constituent knowledge of food safety issues related to beef production and consumption from farm to fork

A new NASA LaRC Multi-Purpose Prepregging Unit

A multi-purpose prepregging machine has been designed and built for NASA Langley Research Center. The machine has numerous advantages over existing units due to its various modular components. Each of these can be used individually or simultaneously depending on the required prepregging method. A reverse roll coater provides the ability to prepare thin films from typical hot-melt thermoset formulations. Also, if necessary, the design allows direct fiber impregnation within the reverse roll coater gap. Included in the impregnation module is a solution dip tank allowing the fabrication of thermoplastic prepregs from solution. The proceeding modules within the unit consist of four nip stations, two hot-plates, a hot-sled option and a high temperature oven. This paper describes the advantages of such a modular construction and discusses the various processing combinations available to the prepregger. A variety of high performance prepreg material systems were produced on IM7 (Hercules) carbon fiber. These included LaRC RP46, a PMR-type resin processed from methanol and two polyamide acids, LaRC IA and LaRC ITPI, prpregged from N-methyl pyrrolidinone (NMP). Parameters involved in the production of these prepreg materials are presented as are the mechanical properties of the resulting good quality laminates. A brief introduction into the existing prepregging science is presented. Topics relating to solution prepregging are identified with a focus on the current research effort and its future development

Weavability of dry polymer powder towpreg

Carbon fiber yarns (3k, 6k, 12k) were impregnated with LARC (tm) thermoplastic polyimide dry powder. Parameters for weaving these yarns were established. Eight-harness satin fabrics were successfully woven from each of the three classes of yarns and consolidated into test specimens to determine mechanical properties. It was observed that for optimum results warp yarns should have flexural rigidities between 10,000 and 100,000 mg-cm. Tow handling minimization, low tensioning, and tow bundle twisting were used to reduce fiber breakage, the separation of filaments, and tow-to-tow abrasion. No apparent effect of tow size or twist was observed on either tension or compression modulus. However, fiber damage and processing costs favor the use of 12k yarn bundles versus 3k or 6k yarn bundles in the weaving of powder-coated towpreg

Processing, properties and applications of composites using powder-coated epoxy towpreg technology

Composite manufacturing using the current prepregging technology of impregnating liquid resin into three-dimensionally reinforced textile preforms can be a costly and difficult operation. Alternatively, using polymer in the solid form, grinding it into a powder, and then depositing it onto a carbon fiber tow prior to making a textile preform is a viable method for the production of complex textile shapes. The powder-coated towpreg yarn is stable, needs no refrigeration, contains no solvents and is easy to process into various woven and braided preforms for later consolidation into composite structures. NASA's Advanced Composites Technology (ACT) program has provided an avenue for developing the technology by which advanced resins and their powder-coated preforms may be used in aircraft structures. Two-dimensional braiding and weaving studies using powder-coated towpreg have been conducted to determine the effect of resin content, towpreg size and twist on textile composite properties. Studies have been made to customize the towpreg to reduce friction and bulk factor. Processing parameters have been determined for three epoxy resin systems on eight-harness satin fabric, and on more advanced 3-D preform architectures for the downselected resin system. Processing effects and the resultant mechanical properties of these textile composites will be presented and compared