Boron fibers have a significant potential to be utilized as structural components for flight / space applications. The key technical issue was to develop a cost effective method to produce continuous boron fibers. MER has accomplished success in that area by utilizing spread, low-cost PANEX 48 K carbon fibers. Subsequently, process conditions were optimized to coat about 1.5 - 2 mum boron on the carbon fibers without spreading. A new technology was developed to produce boron fiber / epoxy composites. The MISSE 6 experiment allowed for the space exposure of the new class of radiation protection technology.

Boron fibers have a significant potential to be utilized as structural components for flight / space applications. The key technical issue was to develop a cost effective method to produce continuous boron fibers. MER has accomplished success in that area by utilizing spread, low-cost PANEX 48K carbon fibers. Subsequently, process conditions were optimized to coat about 1.5 - 2 mu m boron on the carbon fibers without spreading. A new technology was developed to produce boron fiber / epoxy composites. The MISSE 6 experiment allowed for the space exposure of the new class of radiation protection technology.(12)

Over the past fifteen years, MER has had several NASA SBIR Phase II programs in the area of space technology, based upon carbon-carbon (C-C) composites. In addition, in November 2004, leading edges supplied by MER provided the enabling technology to reach a Mach 10 record for an air breathing engine on the X-43A flight. The MER business model constitutes a spin-off of technologies initially by incubating in house, and ultimately creating spin-off stand alone companies. FMC was formed to provide for technology transfer in the area of fabrication of C-C composites. FMC has acquired ISO 9000 and AS9100 quality certifications. FMC is fabricating under AS9100 certification, flight parts for several flight programs. In addition, FMC is expanding the application of carbon-carbon composites to several critical military programs. In addition to space technology transfer to critical military programs, FMC is becoming the world leader in the commercial area of low-cost CC composites for furnace fixtures. Market penetrations have been accomplished in North America, Europe and Asia. Low-cost, quick turn-around and excellent quality of FMC products paves the way to greatly increased sales. In addition, FMC is actively pursuing a joint venture with a new partner, near closure, to become the leading supplier of high temperature carbon based composites. In addition, several other spin-off companies such as TMC, FiC, Li-Tech and NMIC were formed by MER with a plethora of potential space applications.

SiC optics have been considered for numerous optical applications for a long time. The fundamental limitation of monolithic SiC is its, very low fracture toughness which greatly limits its reliability. Long fiber, SiC-SiC composites are an excellent candidate for high end optical application. The selection of the fiber and composite processing needs to address the intrinsic issues of modulus, strength, toughness, thermal conductivity and CTE isotropy. The adaptability and flexibility of SiC-SiC composite manufacturing renders the ability to fabricate very complex, closed-back structures. The fundamental issues associated with uv optics is the ability to polish the substrate to ultra high quality in order to greatly reduce the scattering.

Future space systems developed under NASA Space Initiative need to address the issue of radiation protection in conjunction with multifunctional requirements. The state-of-the-art (SOTA) thermal protection systems are based upon low density carbon insulation and phenolic based ablatives. Such systems are not optimized for radiation resistance. An approach to thermal protection incorporating radiation protection was developed. This new system is based upon boron-foam with a specifically designed, functionally graded thermal protection system

SiC optics has been considered for a very long time. Today, there are a few military and commercial applications. Future imaging and energy transfer applications require robustness on a par with metallic systems. Intrinsic, low fracture toughness of several classes of monolithic SiC is the key impediment in these applications. A new form of SiC-SiC composite for optical applications has been developed. It features high modulus combined with high fracture toughness. This new, highly innovative technology offers the potential in demanding government applications, as well as large surveillance optics (increased toughness can translate into lower aerial density) and high energy commercial lasers. SiC-SIC is a novel technology for optical structures consisting of integrated composite materials and structures which exhibits excellent fracture toughness and homogeneous CTE.

The current generation of laser diodes suffers from poor thermal management. Typically, Cu-W is used as a submount material. Although it offers a good CTE match with GaAs, thermal conductivity is very limited (160 W/mK). A new approach to improving the thermal management of laser diodes was developed involving the use of hybrid C-C/graphite foam composites.We also have a novel technology developed for LIDAR optical structures consisting of SiC-SiC composite material which exhibits excellent fracture toughness and homogeneous CTE.

The nose leading edge of the Hyper-X Mach 10 vehicle was orginally anticipated to reach temperatures near 4000 F at the leading-edge stagnation line. A SiC coated carbon/carbon (C/C) leading-edge material will not survive that extreme temperature for even a short duration single flight. To identify a suitable leading edge for the Mach 10 vehicle, arc-jet testing was performed on thirteen leading-edge segments fabricated from different material systems to evaluate their performance in a simulated flight environment. Hf, Zr, Si, and Ir based materials, in most cases as a coating on C/C, were included in the evaluation. Afterwards, MER, Tucson, AZ was selected as the supplier of the flight vehicle leading edges. The nose and the vertical and horizontal tail leading edges were fabricated out of a 3:1 biased high thermal conductivity C/C. The leading edges were coated with a three layer coating comprised of a SiC conversion of the top surface of the C/C, followed by a chemical vapor deposited layer of SiC, followed by a thin chemical vapor deposited layer of HfC. This paper will describe the fabrication of the Mach 10 C/C leading edges and the testing performed to validate performance.

Abstract Inertial Fusion (IFE) optics presents a unique challenge. Ghoniem provides a mirror design for such an application. The surface has been chosen to be metallic, because dielectric materials exhibit great sensitivity to the effects of ionizing radiation. The leading high reflectivity candidate materials are aluminum, magnesium, silver, gold and copper. To select between these metals the following criteria were used: 1) high reflectivity in the wavelength of interest 2) effects of radiation on absorptivity 3) surface temperature rise during the laser pulse 4) thermal fatigue resistance 5) radiation effects on surface deformation

Future space systems developed under NASA space initiative need to address the issue of radiation protection in conjunction with structural requirements. State-of-the-art (SOTA) technologies such as boron filled polymers are greatly limited in terms of modulus and strength. The addition of boron powder to the polymeric matrix can increase the modulus according to the rule of mixtures (limited by the volume fraction of powder). However, a minimum strengthening of the polymeric matrix is achieved. The use of boron fiber reinforced polymer composites offers an excellent potential in this area. The use of composite materials depending on the load transfer coefficient can utilize up to 50% of the fiber strength. Thus a composite strength in excess of 1 GPa can be attained (compared to just a few ksi for the polymer matrix). The fundamental problem is the lack of a boron fiber in the tow form. A novel technology was developed to address this issue

Currently used laser diodes suffer from poor thermal management. Typically, Cu-W is used as a submount material. It offers a good CTE match with GaAs but its thermal conductivity is very limited (160 W/m-K). A new approach to improving the thermal performance of laser diodes was developed involving the use of hybrid C-C/graphite foam composites.

A novel technology to fabricate lightweight mirrors was demonstrated. A high thermal conductivity carbon-carbon honeycomb composite structure with integrated face sheets was fabricated with P-30X fabric. A 3000degreesC heat treatment was employed to render high thermal conductivity. In addition, a silicon carbide preceramic polymer was utilized to yield a near zero coefficient of thermal expansion (CTE) structure. Subsequently, a 0.5m structure was fabricated. A sol-gel SiO2 coating was applied as an optical surface. A microroughness of 1-2 nm was achieved combined with 4 kg/m(2) areal density. Only passive control was implemented.

A novel technology to fabricate ultralightweight mirrors was demonstrated. High thermal conductivity C-C composite integrated honeycomb face sheets were fabricated using a tape layup. Chemical vapor deposition (CVR)-SiC was employed to produce a functionally graded transition in CTE from about 0 ppm/K to about 4.5 ppm/K A crack free CVR-SiC surface was achieved which was subsequently polished. A 1 kg/m/sup 2/ SiC mirror structure was demonstrated for a 12 cm structure and 1 kg/m/sup 2/ was demonstrated for a 0.5 in structure.

Currently used laser diodes suffer from poor thermal management. Typically, Cu-W is used as a submount material. It offers a good CTE match with GaAs but its thermal conductivity is very limited (160 W/mK). Two approaches to improving the thermal performance of laser diodes were developed:i) the use of diamond-aluminum compositesii) the use of hybrid C-C/graphite foam compositesA novel process was developed to address the interfacial problems in diamond composites. As a result isotropic diamond/Al composites exhibiting 600 W/mK were developed. Carbon-Carbon composites offer good thermal performance but suffer from high anisotropy. In order to alleviate this problem hybrid 1-D C-C/graphite foam composites were developed. Graphite foam offers a good spreading angle while the 1-D C-C composite offers very good conduction towards the heat sink.

Model predictions of the transverse thermal conductivity (Keff) are compared to experimentally determined values as a function of temperature for a commercial 2D-SiCf/SiC made by DuPont from plain weave Hi-NicalonTM fabric and with an ICVI-SiC matrix. Two versions of the DuPont composite were examined: one with a ‘thin’ and one with a ‘thick’ pyrolytic carbon (PyC) fiber coating of thickness 0.110 and 1.044 μm, respectively. Generally good agreement of either the Hasselman–Johnson or the Markworth model predictions (see companion paper, I. Modeling) with measured values of Keff for this composite suggest that these models can be used to predict Keff for composites with various ‘non-ideal’ fiber, interphase and matrix structures. Importantly, the models make it possible to separate the relative component contributions to Keff so that individual component degradation mechanisms can be examined in detail. For the two versions of the well-bonded, as-received DuPont composite made with Hi-NicalonTM woven fabric, at 200 °C constituent values Km=22–25 W/mK (matrix thermal conductivity), Kc≈25 W/mK (PyC-coating thermal conductivity) and heq=2.4×107 W/m2K (equivalent fiber–matrix interfacial thermal conductance) were determined.

SiC ceramics offer unique thermomechanical and optical characteristics. However, their practical application in optics is very limited. A novel approach was developed which combines carbon composites, carbon foam, Chemical Vapor Reaction (CVR)-Si and Chemical Vapor Deposition (CVD)-Si. This unique approach provided for a breakthrough in optical structures the elimination of the print-through at the rib section.

Ultra-lightweight materials are enabling for a number of applications including space-based and transportation. Heretofore, innovative designs using existing materials has been the approach to produce lighter-weight components. Graphite fiber, because of its lightweight and high strength, reinforced composites has been a material of frequent choice to produce lightweight systems. Hollow graphite fibers with the same strength at the same fiber size would be lighter than standard solid graphite fibers and thus would save weight with a potential of up to 50%. They key to achieving large weight savings with graphite fiber composites is to demonstrate a reliable process for producing hollow fibers with high strength.

Carbon/graphite nanotubes represent a near ideal reinforcement for micron size fibers since the nanotube’s size is a few nanometers in diameter with exemplary strengths and stiffness coupled with very light weight. Initial attempts to utilize the various nanotube architectures of single wall (SWNT), double wall (DWNT) and multi wall (MWNT) have resulted in disappointing composite properties that extracted virtually none of the nanotube inherent properties. A major barrier to the fabrication of nanotube reinforced materials and particularly composite micron size fibers has been the effective and efficient dispersion of the nanotubes in the host matrix. Since nanotubes possess a carbon structure, there is good reason to believe nanotubes would be a good reinforcement for a carbon/graphite fiber. Also, a published report [1] of 5% SWNT increased the tensile strength of an isotropic pitch based carbon fiber from 450 to 855 MPA, elastic modulus from 32.5GPa to 80GPa and electrical conductivity by 340%. Pitch is one of the major precursors from which carbon/graphite fibers are produced. Therefore, the goal was to disperse nanotubes into pitch and spin into fibers to determine the affect of nanotubes as reinforcements for carbon/graphite fibers.