Physical and mechanical properties of fiber composite materials consisting of carbon films are described. Application of carbon film structural composites for constructing microwave filters or optical instruments is proposed. Applications in aerospace and architectural structures for high strength and low density properties are discussed

Lippman, M.

Preiswerk, P. R.

English

NASA Technical Reports Server

August 1972	 B72-10423 
NASA TECH BRIEF 
Ames Research Center 	 -4r 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Fabrication of Carbon Film Composites 
for High-Strength Structures 
Fiber-composite materials exhibit very desirable 
physical and mechanical properties because fine fibers 
have qualities that are vastly superior to bulk material 
of the same composition. Similarly, thin films often 
exhibit properties that are substantially different from 
bulk material; in view of this, it has been proposed 
that thin films of selected materials might be used to 
improve the physical and mechanical properties of 
laminated composites. 
Preliminary investigations have shown that the 
density, elastic modulus, and tensile strength of car-
bon films increase dramatically as film thickness is 
reduced from about 3.8 urn to 0.13j.m. For example, 
carbon films have been prepared with an elastic 
modulus of 345 to 896 GN/m2 and ultimate tensile 
strengths of 2.8 GN/m2; the coefficient of thermal 
expansion for the carbon films has been found to be 
close to zero. Moreover, it has been found that the 
high moduli and tensile strengths are retained in 
multiple-layer deposits when individual carbon layers 
are separated by intervening films of titanium. These 
observations indicate attractive potential applications 
of carbon-film structural composites for the construc-
tion of microwave filters or optical instruments which 
are subject to wide temperature variations; the quali-
ties of high strength and low density also imply appli-
cations of the composites in aerospace structures or 
in architectural structures where a high strength-to-
weight ratio is desired. The experimental procedure 
used for the deposition of ultrathin films of carbon 
and titanium in alternating layers is described in the 
following paragraphs.
A substrate (e.g., inert fluorocarbon polymer) ap-
proximately 10 cm x 15 cm in area and 0.013 or 0.007 
mm thick, was cleaned ultrasonically in a deter-
gent bath, followed by rinses in acetone, isopropyl 
alcohol, and deionized water; then, the substrate was 
supported in a metal frame which kept it taut by 
application of a nominal longitudinal tension of 22 N. 
The assembly was placed in a vacuum-deposition 
chamber and maintained at 1500 to 200°C for about 
1 hour at a pressure of 2.7 x 10 N/rn2; the substrate 
was rotated at 60 rpm during deposition so as to form 
essentially equal thicknesses of film on its two sides. 
Electron-beam heating was used to evaporate source 
material; typically, the beam current was held at 150 
to 200 milliamperes. Deposition rate and final thick-
ness were controlled and monitored by means of a 
quartz crystal sensor and associated circuitry. 
Composite films of carbon and titanium were 
formed by using a double-hearth system in the 
electron-beam deposition equipment. At preset inter-
vals, the beam was switched for deposition of either 
carbon or titanium to prodube the desired layered 
deposit. 
Notes: 
1. The following documentation may be obtained 
.from
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Springfield, Virginia 22151 
Single document price $3.00 
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(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19720000422 2020-03-17T03:38:44+00:00Z
Reference: 
NASA CR4972 (N72-17537), Physical Prop-
erties of Thin Films. 
2. No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B 72-10423
Patent status: 
No patent action is contemplated by NASA. 
Source: Peter R. Preiswerk and

Mike Lippman of
Astro Research Corporation

under contract to
Ames Research Center

(ARC-10613) 
B72-10423	 Category 04


Fabrication of carbon film composites for high-strength structures

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