Aircraft are attractive targets for political terrorists.  Specifically, terrorists have placed bombs aboard aircraft to murder passengers and crewmembers that are also aboard the aircraft, and to cause further damage to persons and structures on the ground.  This form of terrorist act often provokes an intense public reaction that has a substantial political impact. 
Despite the use of extremely tight security procedures and sophisticated explosive detecting equipment, terrorists have still been able to place bombs aboard aircraft.  One method used by terrorists to place a bomb aboard an aircraft is to hide the bomb in a passenger's luggage or in other items that are stored and carried in the cargo compartment of the aircraft.  Terrorists have been able to use this method because small bombs cannot be easily detected through ordinary screening methods.  One approach to solving this problem is to institute elaborate and intrusive screening methods.  Another way to deal with this problem is to mitigate the potential damage that could be caused by a small bomb detonating aboard the aircraft. 
In the airline industry, it is a standard practice to place cargo into a containment device, which is commonly referred to as Unit Load Devices (ULDs).  The shape, size and weight of a ULD for a given type aircraft has been fairly well standardized due to practical considerations and regulatory requirements.  Consequently, a typical ULD is in the shape of a box having sloped surfaces that conform the ULD to the aircraft's fuselage when the ULD is placed in the aircraft's cargo compartment.  The ULD is often made of several panels, which are joined together at their edges to surround a cargo hold.  Additionally, the ULD has an opening to provide access to the cargo hold, and a door for covering the opening.  Cargo is placed into, or removed from, the cargo hold through the opening. 
A ULD designed to withstand an explosive blast in the cargo hold should also conform to these practical considerations and regulatory requirements.  Additionally, a blast resistant ULD may include other structures, or be formed from particular materials, to resist an explosive blast.  For example, the panels in a blast resistant ULD may be structured to resist tensile stresses that are directed toward the plane of the panel.  In response to an internal explosion, these panels tend to bulge outwardly from the explosive source but are effective in resisting rupture. 
Stress analysis performed on existing ULDs show that the highest tension stress concentrations caused by an explosive blast within the cargo hold will occur at the edges where the panels have been joined together and at the door around the opening.  Consequently, more material is often added to ULDs at these points of highest tension stress concentration to better contain an internal explosion.  This additional material, however, adds cost and additional weight to the ULD, and may reduce the size of the cargo hold. 
In light of the above, it is an object of the present invention to provide a containment device that is able to resist an internal explosive blast without rupturing the device.  Another object of the present invention is to provide a containment device that reduces tension stress concentrations caused by an internal explosive blast.  Yet another object of the present invention is to provide a containment device that meets the regulatory standards for the use of such devices in air transport operations.  Still another object of the present invention is to provide a containment device that allows relatively easy access to a cargo hold located inside the cargo container.  Another object of the present invention is to provide a containment device that is easy to use, relatively easy to manufacture, and comparatively cost effective.