Dies of a phenolic molding compound with chopped glass fibers as fill material possess a flexural strength of 20,000 psi and a compressive strength of 28,500 psi

Bush, S.

Caseldine, H.

Smith, R. H.

English

NASA Technical Reports Server

May 1970	 Brief 70-10273 
NASA TECH BRIEF 
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 Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Lightweight, High-Strength, Reinforced Plastic Tube-Franging Die 
Energy absorption by tube franging (the breaking 
of a tube at a predetermined rate by an impact load) 
has been considered for soft-landing of air-dropped 
payloads. A similar application is the collapsing 
steering column in motor vehicles. However, in the 
case of the air drop, two important considerations 
exist that are not involved in the motor vehicle: light 
weight and rf transparency (in the case of radio trans-
mitting or receiving equipment). 
Previously, metal tubes and franging dies (see 
NASA Tech Brief 63-10304) have been used, but 
neither the aluminum frangible tube nor steel die is 
ri-transparent and each imposes a weight penalty. 
The importance of the dies cannot be overempjiasized 
since they distribute the shock loads to the tube ends, 
and must be designed so that maximum use of the 
tubes' shock-absorbing capacity is realized. 
In certain air-drop planning, a target compressive 
franging stress of 20,000 psi was required for the 
shock-absorbing tubes, and a compressive strength 
above this value had to be used for the material. Low-
cost cast epoxy dies were considered inadequate, but 
a commercially available phenolic molding compound 
with chopped glass fibers as fill material was found to 
meet weight and strength requirements. Matched 
die metal molds were used, and the die material was 
subjected to a molding pressure in compression be-
tween 200 and 2,000 psi at temperatures between 290° 
and 340° F, with a cure time of 2 mm.
Notes: 
1. Mechanical properties of dies of this material are: 
a flexural strength of 20,000 psi and a compressive 
strength of 28,500 psi. 
2. Tube-franging action with these dies is as good as 
that obtained with steel dies six times as heavy, 
and the franging groove remains polished and 
undeformed after repeated tests. 
3. This technique would be useful as a shock-absorb-
ing medium for highway guard rails where the 
rustproof property would reduce maintenance. 
4. The following documentation may be obtained 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-CR-66301 (N67-21178), The 
Design and Development of Radio Fre-
quency Transparent Omnidirectional 
Energy-Absorbing Element Systems 
Patent status: 
No patent action is contemplated by NASA. 
Source: Ronald H. Smith, Harold Caseldine, 
and Sellers Bush of 
The Northrop Corp. 
under contract to 
Langley Research Center 
(LAR-10126) 
Category 04 
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 free from privately owned-rights.
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Lightweight, high-strength, reinforced plastic tube-franging die

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