A new bonding method using vacuum, pressure and heat, which produces a bond line free of voids, is described. This method is very successful in bonding ablation shields to a magnesium structural component in simulated reentry tests involving great heat and air turbulence

King, C. B.

English

NASA Technical Reports Server

October 1964
	 ^ \q- 72* 
Brief 63-10558 
NASA TECH BRIEF	
-4 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint 
industry with the technical content of an innovation derived from the space program. 
New Method Forms Bond Line Free of Voids 
Vacuum-Pressure Vessel 	 cturaI Component 
Adhesive 
,Facing Material 
Adhesive	
- Vacuum 
Vacuum Gage
Pressure 
Bonding Fixture Not Shown 
The problem: The advent of epoxy resins has 
greatly increased the use of adhesive bonding as a 
structural technique. In structural applications in-
volving high vibrational, impact, or heat environ-
ments, voids or air pockets in the bond line introduce 
weaknesses that endanger the integrity of the bond. 
The solution: A bonding method employing 
vacuum, pressure, and heat produces a bond line es-
sentially free of voids or discontinuities. 
How it's done: The structural component and 
facing material are prepared for the bonding operation 
by machining and measuring their interfacing surfaces 
as held in a bonding fixture to assure a minimum bond 
line gap of 14 mils. The assembled components and 
fixture, fitted with a reservoir dam, vacuum gageline, 
and adhesive feeder line, are placed in an oven and 
heated to 200'F. The complete assembly is removed
from the oven and placed in a vacuum-pressure vessel 
heated to 200°F and the vacuum gageline and adhesive 
feeder line attached through the vessel wall to external 
counterparts. The vessel is evacuated and the proper 
quantity of de-aerated epoxy adhesive is forced into 
the bond line gap. The vacuum is relieved and the ves-
sel is pressurized to 90 psi using dry nitrogen. The 
vessel is held at 200°F and 90 psi for the 16-hour 
curing period. Following the curing period the 
assembly is allowed to cool inside the vessel, which is 
maintained at 90 psi during this cooling cycle. The 
assembly is then removed from the vessel and fixture. 
Notes: 
1. X-ray inspection proved the bond line to be com-
pletely free of voids. 
2. An ablation shield bonded to a magnesium struc-
tural component by this method has proven highly 
(continued overleaf) 
This document was pre pared under the sponsorship of the National 	 this. document, or that the use of any information, apparatus, method, 
Aeronautics and Space Administration. Neither the United States Govern-	 or process disclosed in this document may not infringe privately-owned 
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 	 rights; or B. Assumes any liabilities with respect to the use of, or for 
any warranty or representation, express or implied, with respect to the	 damages resulting from the use of, any information, apparatus, method, 
accuracy, com pleteness, or usefulness of the information contained in 	 or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19630000108 2020-03-11T16:48:24+00:00Z
successful in simulated reentry tests involving great 
heat and air turbulence. 
3. This method would be useful where the structural 
strength of metal is required but other surface 
materials are indicated by environmental condi-
tions. 
4. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Langley Research Center 
Langley Station 
Hampton, Virginia, 23365 
Reference: B63-10558
Patent status: NASA encourages the immediate 
commercial use of this invention, it is owned by 
NASA, and a patent application has been filed. When 
patented, royalty free nonexclusive licenses for its 
commercial use will be available, inquiries concerning 
license rights should be made to NASA Headquarters, 
Washington, D.C., 20546
Source: Charles B. King 
(Langley-20) 
Brief 63-10558


New method forms bond line free of voids

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