A series of lightweight (density below 2.0 gm/cm3) composites has been manufactured that have controllable properties. The core composite has been improved to provide higher strength (similar to aluminum), extremely low density, receptivity to exterior coatings, and highly designable properties. The composite is made in days, is machinable and formable, can be joined/threaded, can be exposed to various environments (temperature, radiation), and is easily made into many parts. Lightweight mirrors for space and IR applications are extremely important. The goal of this work was to create lightweight multifunctional composites for replacement of titanium, beryllium, Invar, aluminum, rubber, and graphite epoxy for structural, mirror, and non-structural components. The key characteristics of this tailorable composite are low density, high stiffness (up to 25 MSI modulus), variable/low coefficient of thermal expansion (CTE) (2 to 7 ppm/°C), high temperature refractory materials and variable thermal conductivity. The composites are easily made (time to completion of 7 to 10 days), joinable, threadable, machinable to 80 mils, durable to resist FOD (foreign object damage), ductile enough to behave like a metal, and relatively low in cost.

This material involves the use of powders-matrix composition, and/or a coated microsphere (hollow particle). The new material is developed from hollow ceramic spheres that are lightweight and have high crush strength. When a metallic coating is applied to the ceramic spheres, the material behaves like a metal, and can be shaped/formed and pressed together into a metal matrix composite. Coatings may be applied to the matrix to improve property control. Because of the high-strength hollow spheres, this pressed composite can be forged, spark plasma sintered (SPS), or hot isostatic pressed (hip’d) into high-strength parts. The hollow spheres can also be coated with other materials to help shield from radiation and EMI (electromagnetic interference) while reducing CTE and potential materials mismatch problems.

From early 3- and 6-in. (7.6- and 15.2-cm) diameter blocks to the 12- and 16-in. (30.5- and 40.6-cm) diameter pieces used for small structures and mirrors, the material has developed into machinable (EDM or conventional) components. More recently, high volumes of the material have found application in several down-hole oil and gas applications.

This work was done by Dean Baker of Advanced Powder Solutions, Inc. for Goddard Space Flight Center. GSC-16113-1

NASA Tech Briefs Magazine

This article first appeared in the February, 2015 issue of NASA Tech Briefs Magazine.

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