JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009 - 55

Furthermore, the application of external pressure usually means “sand” or “shot bags”, both of which create a big “heat-sink”, and the pressure is not uniformly applied over the repair area. Would we really want to return that flap to the autoclave for repair if there was a way of applying localized heat and sufficient pressure? If an autoclave just happened to be available locally it would still be both a time-consuming and extremely expensive exercise as these devices are certainly not cheap to operate. Imagine the cost of having to heat the total volume of this autoclave in order to carry out a repair measuring no more than 30.48 cm x 25.4 cm. Besides having to pressurize it, if the cure temperature is in excess of 120°C, nitrogen or another inert gas would be recommended as the pressure media in order to eliminate the risk of fire in the autoclave. The installation and operation of a nitrogen generation plant, or the rental of “bottled gas”, adds to the expenses. Fig. 2: Localized heating. Main features • Semi-portable and easy to use • Cost-effective to operate and low capital expenditure • Control system based on the industry-preferred HCS9200B Hot Bonder Localized heating The RepairClave is a pressure vessel, but instead of heating the total volume to achieve the cure temperature, localized heat is applied by the same silicone rubber heater blanket that is used in the Hot Bonder repair. Two independent 30 amp zones are provided so that more than one repair can be carried out at the same time, or the power supply to the two zones can be combined to carry out a much larger repair. Because only the actual repair area is heated, the volume of air inside the vessel never reaches cure temperature and therefore the cost of using an inert gas is not incurred. Localized heating also means that the vessel does not need a double-walled construction as there is no need for the hot air to be circulated in order to achieve temperature uniformity. Like in the autoclave process, the part is introduced into the RepairClave under vacuum. This vacuum can be vented at anytime during the operation in compliance with the cure processing procedure (Figure 2). Pressure is applied using standard, filtered “shop air” at 5 to 7 bar and the configuration can be fully customized to meet customer specifications. Being a pressure vessel, it is manufactured in accordance with international standards such as ASME (American Society of Mechanical Engineers) for the American domestic market. The RepairClave is a lighter construction than an autoclave because the door does not need to incorporate a deflector plate in order to “bounce back” the circulated hot air over the part. This means that a much more cost-effective manual clamping arrangement can be used. Though the internal pressure would prevent the door from being inadvertently opened during operation, it is nevertheless fitted with an external visual warning when pressurized, as with all pressure vessels. For ease of access, the internal interface panel is located just inside the door opening and comprises connections for both zones. Configurations built to date have provided for single- and three-phase power, vacuum supply and monitoring, plus ten thermocouple connections for each zone in compliance with the latest SRM requirements. However, this interface panel can be modified to meet individual customer requirements (Figure 3). Fig. 3: Internal interface panel. The programmable heating controller is located above the electrical panel, to the left, while the vacuum and pressure panel is to the right (Figure 4). As silicone rubber heater blankets are being used, a slightly modified Hot Bonder is utilized for controlling the curing process. Apart from being re-housed, the only difference No53 November - December 2009 / jec composites magazine

JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009