Introduction of metal foil as part of matrix and fiber composite, or ""sandwich'', improves strength and stiffness for multidirectional loading, improves resistance to cyclic loading, and improves impact and erosion resistance of resultant fiber-composite hybrid structure

Chamis, C. C.

Lark, R. F.

Sullivan, T. L.

English

NASA Technical Reports Server

TITANIUM Foil (Ti) 
ADHESIVE (TN 1000) 
BORONIALUMiNUM (A/Al) 
GRAPHITUFEPDXY (A-S/U)
December 1974	 B74-10247 
NASA TECH BRIEF 
Lewis Research Center 	 C 
NASA Tech Briefs announce new technology derived from the US 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 
Advanced Fiber-Composite Hybrids —

A New Structural Material 
The Problem: 
Advanced fiber/resin and fiber/metal matrix con-
posites are used most efficiently when the fiber and lOLI 
directions are coincident. To provide strength or stiffnc.-
in more than one direction, composites with fihci 
oriented in several directions are necessary. Orienting 
fibers in more than one direction in the same compositc, 
however, increases the fabrication complexities, reduces 
their efficiency, and can introduce lamination residual 
stresses comparable to the transverse and shear strength 
properties of the unidirectional composite. These lamini-
tion residual stresses may limit the resistance of the 
composite components to mechanical loads. In particukii 
it may reduce their resistance to thermal and/or mechani-
cal cyclic load. In addition, commercially available 
graphite-fiber/resin and boron-fiber/aluminum composites 
are inherently weak in impact and erosion resistance. 
The Solution: 
Introduction of a metal foil as part of a matrix and 
fiber composite, or "sandwich," improves strength and 
stiffness for multidirectional loading, improves resistance 
to cyclic loading, and improves impact and erosion 
resistance of resultant fiber-composite hybrid structure. 
How It's Done: 
Unidirectional fiber composites made from graphite-
fiber/epoxy and boron-fiber/aluminum and a few stra-
tegically located titanium foil layers were adhesively 
bonded to form the metal and resin matrix fiber com-
posite hybrid (see sketch). 
.-
 
FIBER DIRECTION 
.5 - St	 heiis,iy'0d metal matrix and ,in matrix fiber	 Svbr,5
);J 
Type V Ti/(B/Afl/(A.S/E). 
S - Photomicrographs of composite 
specimen cross sections. 
Magnification, 50X. 
Laminates were made using various combinations of 
the above composite systems. Specimens from these 
laminates were subjected to tensile, flexure, Izod impact, 
and notch-sensitivity tests. Laminate analysis was used to 
calculate the lamination residual stresses throughout the 
hybrids. The results obtained were compared with those 
of unidirectional materials with respect to impact resist-
ance, notch-sensitivity, transverse strength, and ease of 
fabrication. 
Mechanical tests of adhesively-bonded composite 
hybrids showed that it is possible to make a composite 
with the following desirable properties: 
I. Longitudinal strength and stiffness approaching 
corresponding properties of other advanced fiber com -
posites; 
2. Transverse flexural strength approaching that of the 
yield strength of titanium alloy, T1.6A14V; 
3. Longitudinal impact resistance approaching that of 
aluminum; 
4. Transverse and shear stiffnesses comparable to those 
of 6061 aluminum; and 
5. Density comparable to that of commercially-
available E-glass/epoxy composites. 
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration Neither the United States
	 information contained in this document, or warrants that Such use 
Government nor any person acting on behalf of the United States
	 will be tree from privately owned rights
https://ntrs.nasa.gov/search.jsp?R=19740000247 2020-03-17T13:59:33+00:00Z
Notes: 
1. The lamination residual stresses in the adhesive are 
about 50 percent of its corresponding failure stresses, 
therefore, capacity remains in the hybrid composites 
for carrying mechanical load. 
2. Judicious location of the titanium-foil layers in the 
laminates may result in predictable high energy absorp-
tion failure modes for these hybrids. 
3. These types of hybrids may be designed to have 
inherent fail safe characteristics. 
4. These types of hybrids should be of interest to 
designers and fabricators of structural components 
designed to meet a multitude of strength and environ-
ment requirements. 
5. Further information is available in the following 
report: 
NASA TM-X-71580 (N74-30002), 
Boron/Aluminum-Graphite/Resin Advanced Fiber 
Composite Hybrids 
Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812-337-7833 
Reference: B74-10247 
6. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B74-10247
Patent Status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
NASA Patent Counsel 
Mail Stop 500-113 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Source: C.C. Chamis, R.F. Lark, 
and T.L. Sullivan 
Lewis Research Center

(LEW-121 18)
. 
B74-10247	 Category 04


Advanced fiber-composite hybrids--A new structural material

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