Prestressed segmented brittle materials in aerospace structure

Hermann, P. C.

English

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August 4, 1964 
a 
t ITHRU) (ACCESSION NUMBER) 
e & 
Headquarters  (PAGES) 
National Aeronautics and 
1520 H. Street ,  N. W. 
Washington 25, D. C. 
Spac e Administration (CATEGORY) 
Attention: Mr. Norman J. Mayer 
Subject: NASA Contract No. NASr-65(04) 
Fifth Quarter ly  Status Report 
IITRI Projec t  M 6046 
"Applications of P r e s t r e s s e d  Segmented 
Bri t t le  Materials in Aerospace Structures".  
G entl e m  en : 
With the extension contract  in effect as of June, our  initial efforts 
W e  
The problem is being attacked 
have been directed towards resolving the segment interface problem. 
consider this to be the central  problem in  quantitatively prediciting the 
behavior of simple p re s t r e s sed  members .  
f r o m  two points of view: (1) Attempting to achieve perfect  contact between 
segments ;  (2)  Determining methods to predict  equivalent contact areas 
and the i r  subsequent equivalent moments of iner t ia  for  imperfect contact 
between segments.  
In our investigation of methods of producing "perfect interface 
match  up", we have been unable to locate a source  of g lass  segments with 
the required flatness and efforts to s l ice  up glass  blocks into matching 
segments  have not produced satisfactory sur faces .  
go to T ic  precis ion gage blocks which can be readily obtained with a 
f la tness  of one-half light band on the 1" x 2" surfaces  of the 1" x 2" x. 25" 
size .  These gage blocks will be combined to f o r m  a beam approximately 
20" long. 
We have decided to 
When imperfect  contact exists between segments ,  it becomes 
necessa ry  to modify the theory. 
of imperfect  contact is by utilizing effective propert ies  such as a n  effective 
The eas ies t  way of incorporating the effects 
https://ntrs.nasa.gov/search.jsp?R=19650019875 2020-03-17T01:57:34+00:00Z
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Headquarters  
National Aeronautics 
and Space Administration 
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August 4, 1964 
Page  2 
c r o s s  sectional a r e a  and its effective moment of inertia.  
propert ies  may be  determined experimentally. The effective c r o s s  
sectional area may be  deduced f rom the load-deflection curves  of a 
segmented column using the monolithic value of the modulus of elasticity. 
Similar ly  the effective moment of inertia can be deduced f r o m  a te rmina l  
couple-end rotation curve of a segmented beam. 
These effective 
Research  under the original contract  indicated that the ult imate 
s t r e s s  obtainable in a segmented column was dependent upon the s i ze  of 
the segments  - sma l l e r  s i ze  corresponding to l a rge r  s t r e s s .  Consequently 
i t  is anticipated that the effective area-effective moment of iner t ia  problem 
will a l so  exhibit s i ze  dependence. 
being designed to measu re  the s i ze  effect. 
ex t reme value statistics to analyze perhaps both the s i ze  effect and the 
relationship between the effective moment of iner t ia  and the effective c r o s s  
sectional a r e a .  
Experiments on var ious s i ze  columns a r e  
Also it may be possible to use 
In another a r e a ,  work i s  currently in  p rogres s  to design tes t s  to 
As compare  with the theory of p re s t r e s sed  monolithic br i t t l e  members .  
current ly  envisioned, 100 to 200 nominally identical p las te r  beams will 
be p r e s t r e s s e d  and loaded to failure. 
Re spec t f ully s ubmi t t ed , 
IIT RESEARCH INSTITUTE 
PCH / j a c  
Reviewed by: 
Ralp$l P r o  ec t  L. Manager Bar n tt 
Paul  C. Hermann 
Assis tant  P ro jec t  Engineer 


Applications of prestressed segmented brittle materials in aerospace structures

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