Lightweight composite has high specific strength and stiffness and remains effective under extreme environmental conditions. Use as engineering material is feasible because it has excellent mechanical properties and is easily produced within small tolerances on constituent volume fractions. Main benefit of composite is its improved longitudinal strength and modulus

Evensen, H. A.

English

NASA Technical Reports Server

July 1971	 .	 Brief 71-102.17 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
-. 
Promising Boron/Graphite /Resin Composites 
A program was conducted to develop lightweight 
structural composites that would have high specific 
strength and stiffness and would remain effective 
under extreme environmental conditions. Effort was 
specifically directed to an analytical and experimental 
investigation of a specially developed, mixed (hybrid) 
composite consisting of boron and graphite fibers in 
an epoxy matrix. Emphasis was placed on the mixed 
composite with intermingled fibers, rather than a 
laminated composite with alternating layers of dif-
ferent prepregs (combinations of resins and reinforce-
ments in easy-to-handle sheet or other form). 
As a result of this program, the following conclu-
sions were reached: 
1. The boron/graphite/epoxy mixed composite is a 
feasible engineering material in that it possesses 
excellent mechanical properties and can be easily 
produced within small tolerances on the constitu-
ent volume fractions. 
2. Despite the improved transverse tensile modulus 
and in-plane shear modulus of the boron /graphite/ 
epoxy hybrid, these improvements are not of suf-
ficient magnitude to warrant changes in present 
conservative design procedures. The main benefit 
to be gained from this composite lies in its improved 
longitudinal strength and - modulus. However, sim-
ilar improvements can be obtained by increasing 
the boron volume fraction on boron/epoxy com-
posites alone. The use of the mixed composite as a 
replacement for the boron/epoxy composite would 
be unjustified unless the fiber mixing process could 
be achieved at very little additional cost. 
3. The most feasible applications of the boron/graph-
ite/epoxy composite are in areas where other exist-
ing composites have shortcomings. One such ap-
plication, developed in this program, is that of 
transitioning the hybrid composite between rela -
tively stiff boron/epoxy load-bearing elements and 
more-workable graphite/epoxy closeout sections. 
Two basic transition combinations of this type were 
fabricated and tested, and were shown to yield 
strong, aerodynamically smooth, adhesive-free 
transitions in a single curing process. 
Notes: 
1. Specific technical questions may be directed to: 
Technology Utilization Officer 
Code A&TS-11J 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
2. The following documentation may be obtained 
from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: 
NA SA-CR- 102944 (N71-14267), Boron/ 
Graphite Hybrid Composite Development 
Study 
Patent status: 
No patent action is contemplated by NA SA. 
Source: H. A. Even sen of

Whittaker Corp.

under contract to

Marshall Space Flight Center
(MFS-21 126) 
Category 04,08 
This documefct was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000216 2020-03-17T02:19:11+00:00Z


Promising born/graphite/resin composites

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