(OOA), Vacuum Bag Only (VBO)

TECH Tidbits
Out-of-Autoclave (OOA), Vacuum Bag Only (VBO) and –
“Not-in-the-Autoclave”
Dr. Scott W. Beckwith, SAMPE International Technical Director
and President, BTG Composites Inc.
Taylorsville, UT
During the recent conference events, the topic of numerous technical papers has been titled as OOA or VBO – “Out-of-Autoclave”
and “Vacuum Bag Only”. Although the terms have been used more frequently on paper titles, and in panel sessions, mostly
within the last 4-6 years, the technology has been advancing for the past 15 years or so. The technologies associated with preimpregnated (“prepreg”) materials used in non-autoclave pressure systems and processes, have gained momentum since many
“tooling” materials started being used for making prototype structures.
To many M&P engineers the terms OOA and VBO have come to mean many different things since numerous composites processes
can often be produced without ever seeing an autoclave. For example, the list of composites manufacturing processes is long if
one considers the term “OOA” to actually mean “never in the autoclave”, or “autoclave never needed” or technically “outside
of the autoclave.” Under that more encompassing definition, the following composites manufacturing methods, except in very
rare instances, have long been “OOA” using that loose criteria:
• Filament Winding
• Pultrusion
• Resin Transfer Molding (RTM)
• Vacuum Assisted RTM (VARTM)
• Most Vacuum Infusion Processes (VIP)
• Compression Molding
• Belt-Wrapping • Roll-Wrapping
• Thermoforming
• Contact Molding
• Chop and Spray
• Quickstep™
• Some Vacuum Bagging Processes
• Bladder Molding
• Seemann’s Composite Resin Infusion Process (SCRIMP)
OOA and VBO processing have truly been focused on the use of prepreg materials cured under a vacuum pressure. As such, there
has been a very significant amount of work done by both material suppliers and composites manufacturers who are interested
in speeding up the production process while at the same time achieving “autoclave material performance and overall quality”.
The numerous SAMPE technical papers from our conference proceedings reflect the advances made by both groups over the
last several years. For example, two of the earliest OOA products are shown in Figure 1 a, b.
OOA and VBO technology will continue to play an important part in composites processing. The techniques employed by both
of these approaches (whether one uses a vacuum bag or not), is certainly an attempt to improve processing efficiency as we
enter an age where production quantities are getting much larger and cycle times require drastic shortening in order to meet
demand. Both materials and processes require conformance to qualities previously achieved mainly via an autoclave route. Low
void contents, consistent fiber-resin ratio demonstration, excellent temperature and mechanical property demonstration, and
composite part consistency in all designed parameters remain important parameters to control.
Processes which fall outside the OOA and VBO definitions above, those that have been traditionally “Outside of the Autoclave”,
still will play an important part in the future. In many cases these processes already address high production volume and low
cost aspects of our community.
(a)
(b)
Figure 1. (a) Boeing Launch Vehicle Fairing (left) and (b) Lockheed/AFRL X55A Aircraft (right).
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SAMPE Journal, Volume 50, No. 2, March/April 2014

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