Continuous fiber thermoplastic prepreg

A pultrusion machine employing a corrugated impregnator vessel to immerse multiple, continuous strand, fiber tow in an impregnating material, and an adjustable metered exit orifice for the impregnator vessel to control the quantity of impregnating material retained by the impregnated fibers, is provided. An adjustable height insert retains transverse rod elements within each depression of the corrugated vessel to maintain the individual fiber tows spread and in contact with the vessel bottom. A series of elongated heating dies, transversely disposed on the pultrusion machine and having flat heating surfaces with radiused edges, ensure adequate temperature exposed dwell time and exert adequate pressure on the impregnated fiber tows, to provide the desired thickness and fiber/resin ratio in the prepreg formed. The prepreg passing through the pulling mechanism is wound on a suitable take-up spool for subsequent use. A formula is derived for determining the cross sectional area opening of the metering device. A modification in the heating die system employs a heated nip roller in lieu of one of the pressure applying flat dies

Comparison of flexural properties of aramid-reinforced pultrusions having varied matrices, pretreatments and postcures

Aramid-reinforced composite materials of equal fiber volume and varied polymer thermoset matrices were pultruded and flexurally tested to failure. The objective was to improve the flexural properties of aramid-reinforced pultrusions. Pultrusions of both sized and unsized aramid fiber with four different resin systems were compared to determine the effects of sizing compounds and postcuring on flexural strength, fiber wettability, and fiber-to-resin interface bonding. Improvements in flexural strength resulting from pretreatments with the sizing solutions used were marginal. The most significant improvements in flexural properties resulted from postcuring. Flexural strengths ranged from a low of 39,647 psi (273MPa) to a high of 80,390 psi (554 MPa), an overall increase of 103 percent. The fact that postcuring improved the flexural properties of the pultrusions of the four resin systems indicates that a full cure did not occur in any of the resin systems during the pultrusion process. The increased flexural strengths of the polyester and vinyl ester pultrusions were the most surprising. The four resin systems examined were Interplastic Corporation VE 8300 vinyl ester, Ashland Chemical Company Aropol 7430 Polyester, and Shell Chemical Company Epon 9302 and Epon 9310 epoxides

Potential for on-orbit manufacture of large space structures using the pultrusion process

On-orbit manufacture of lightweight, high-strength, advanced-composite structures using the pultrusion process is proposed. This process is adaptable to a zero-gravity environment by using preimpregnated graphite-fiber reinforcement systems. The reinforcement material is preimpregnated with a high-performance thermoplastic resin at a ground station, is coiled on spools for compact storage, and is transported into Earth orbit. A pultrusion machine is installed in the Shuttle cargo bay from which very long lengths of the desired structure is fabricated on-orbit. Potential structural profiles include rods, angles, channels, hat sections, tubes, honeycomb-cored panels, and T, H, and I beams. A potential pultrudable thermoplastic/graphite composite material is presented as a model for determining the effect on Earth-to-orbit package density of an on-orbit manufacture, the package density is increased by 132 percent, and payload volume requirement is decreased by 56.3 percent. The fabrication method has the potential for on-orbit manufacture of structural members for space platforms, large space antennas, and long tethers

Will Continued Monitoring Of Beaver Damaged Resources Minimize Future Damage?

The purpose of this study was to determine if continued monitoring and removal of beavers (Castor canadensis) from previously controlled beaver damage sites resulted in less additional damage than not monitoring such sites. Beavers were removed from 34 sites in nine southeast Texas counties from August 1996 through March 1997. Sixteen sites subsequently were monitored monthly and, if beavers had reinvaded, they were removed and the additional damage value was recorded. The remaining 18 sites were not monitored monthly, but they were visited for a final survey at the end of the study. The value of additional damage was recorded at that time. Damage following reinvasion occurred more often when sites were not monitored (5 of 7 sites, compared to only 2 of 7 reinvaded, monitored sites). In addition, when damage occurred at reinvaded sites, monetary value appeared to be greater without monitoring (average $940, n=5) than with monitoring (average$125, n=2). The larger average damage values for reinvaded unmonitored sites compared to reinvaded monitored sites would be important to landowners when deciding if property should be monitored. Factors that made some sites susceptible to reinvasion were also evaluated. Significantly more beavers were taken initially, per site, in the reinvaded sites compared to all other sites. This implies that better habitat and higher beaver density were the most important factors in determining a site\u27s susceptibility to reinvasion

Will Continued Monitoring Of Beaver Damaged Resources Minimize Future Damage?

The purpose of this study was to determine if continued monitoring and removal of beavers (Castor canadensis) from previously controlled beaver damage sites resulted in less additional damage than not monitoring such sites. Beavers were removed from 34 sites in nine southeast Texas counties from August 1996 through March 1997. Sixteen sites subsequently were monitored monthly and, if beavers had reinvaded, they were removed and the additional damage value was recorded. The remaining 18 sites were not monitored monthly, but they were visited for a final survey at the end of the study. The value of additional damage was recorded at that time. Damage following reinvasion occurred more often when sites were not monitored (5 of 7 sites, compared to only 2 of 7 reinvaded, monitored sites). In addition, when damage occurred at reinvaded sites, monetary value appeared to be greater without monitoring (average $940, n=5) than with monitoring (average$125, n=2). The larger average damage values for reinvaded unmonitored sites compared to reinvaded monitored sites would be important to landowners when deciding if property should be monitored. Factors that made some sites susceptible to reinvasion were also evaluated. Significantly more beavers were taken initially, per site, in the reinvaded sites compared to all other sites. This implies that better habitat and higher beaver density were the most important factors in determining a site\u27s susceptibility to reinvasion

Pultrusion Die Assembly

This invention relates generally to pultrusion die assemblies, and more particularly, to a pultrusion die assembly which incorporates a plurality of functions in order to produce a continuous, thin composite fiber reinforced thermoplastic material. The invention is useful for making high performance thermoplastic composite materials in sheets which can be coiled on a spool and stored for further processing

Trade policy, standards, and development in Central America

After reviewing the current state of standards and trade in Central America, the authors suggest top priorities for reform from a trade policy perspective in a new and increasingly important area of public policy and development. They conclude that it makes sense to: a) take a regional rather than a national approach to setting up accreditation, testing, and metrology infrastructure - to share equipment, experts, and information to get more bang out of limited funding; b) promote regional bodies as venues for Central American countries to develop common positions in international discussions of the development of standards; c) regionalize information-gathering efforts and use information technology to disseminate that information rapidly; and d) push for a sunset clause in international standards developments, because standards have value only if adopted and used.Administrative&Regulatory Law,Environmental Economics&Policies,Labor Policies,Trade and Regional Integration,Health Economics&Finance

Surface cleaning technologies for the removal of crosslinked epoxide resin

This study provides details of the use of laser ablation and sodium hydride cleaning processes for the removal of crosslinked epoxide and other residues from resin transfer moulding (RTM) tool substrates, as used in the aerospace industry. The requirement for removal of such contamination is so that the mould can be re-used, following the subsequent application of an external release agent. These tools are, typically, fabricated from steel, nickel or CFRP composite materials; this paper focuses on the use of nickel substrates. The requirement to clean large surface areas quickly to satisfy commercial restraints, compromises the degree of absolute cleanliness that can be obtained. However, in applications where cleaning time is not a constraint, laser cleaning can be a very gentle and efficient process; typically Nd:YAG lasers find application in this area. In contrast, high power lasers are desirable for industrial scale applications where large areas need to be cleaned quickly. In this instance pulsed CO2 lasers can be used. The use of sodium hydride was also found to be highly successful in removing crosslinked organic contamination providing that suitable hard rinse and drying operations were also carried out