Description of the FRC Cargo Hold Liner (CHL) Design Concept

The FRC cargo hold liner design is historically based on independent research and development activities directly related to the application of Äber reinforced polymer matrix composite materials to the construction of military land combat vehicle hull structures. The research, conducted over the last two decades, by research staff now at FRC, has conclusively demonstrated the superiority of composite hull construction in defeating kinetic energy (fragmentation) as well as mine blast threats encountered by land combat vehicles on today’s battleÄelds. The technology described herein is being used today in the construction of vehicle platforms for the DARPA/ARMY Future Combat System (FCS) Program. Such an approach offers a solution unique to the armor industry, namely, increased protection while simultaneously reducing weight relative to conventional construction. Consequently, composite vehicle hull construction becomes the enabling technology for FCS vehicles to achieve rapid deployment capability by becoming C-130 air-transportable.

In order to simultaneously defeat blast and fragmentation threats at minimum weight, the FRC CHL is constructed as a segmented, three piece, self-contained pressure vessel. The pressure vessel is fabricated inside the aircraft’s cargo hold by laying up successive plies of 60 inch wide overlapping woven fabric broadgoods to the required wall thickness. The plies are laid-up and bagged on a collapsible tool surface and cured inside the cargo hold using the Vacuum Infusion Process (VIP). This is a closed cell curing process by which the release of volatile organic compounds (VOC’s) is negligible and maintained well below EPA exposure limits. After the in-situ curing of parts is completed, cured segments of the pressure vessel are removed from the collapsible tool and assembled inside the aircraft’s cargo hold. After assembly of the segments, the CHL becomes a self-contained protective boundary (i.e. vessel) with its own door. The CHL is attached to the floor of the cargo hold whereby dilation of the vessel is permitted during explosive detonation. Such dilation allows the CHL to expand (approx. 12 mm on each side) without contacting the fuselage of the aircraft’s cargo hold, while simultaneously preventing fragmentation threats from penetrating.

Theory of Operation

The FRC cargo hold liner design concept incorporates a novel composite material system used in composite military vehicles. The laminate architecture optimizes strength requirements (i.e. overpressure due to explosive blast) as well as ballistic (i.e. kinetic energy fragmentation) requirements. This is accomplished by the application of a proprietary Äber coating, which develops a viscoelastic bond at the cured Äber/resin interface.

Materials Proposed for CHL Fabrication

Two composite laminate solutions are available, each offering slightly different costs and beneÄts. Both composite solutions incorporate the same resin matrix, which utilizes a different type of Äber reinforcement. Resin selected for the FRC CHL is highly resistant to attack by harsh chemical agents or solvents. This is further substantiated by the use of this resin in the fabrication of containers used by the chemical industry for the storage of extremely caustic acids and bases. Consequently, such a composite laminate is ideally suited as a liner within aircraft cargo holds where spillage or leakage of unwanted or unanticipated caustic cargo could potentially cause signiÄcant damage to the aircraft.

With regard to Äber reinforcement, the FRC CHL solution offers two choices, namely, an aramid (i.e. Kevlar) Äber solution or an S-2®Glass Äber solution. The acquisition cost for the aramid solution is higher but also offers a lighter weight solution relative to the S-2®Glass solution. On the other hand, the aramid solution exhibits a higher repair, maintenance and life cycle cost relative to the S-2®Glass solution.

The following wall thicknesses and weights are applicable to the FRC CHL design:
• Thickness: ranging from 6 to 12 piles of laminate (4mm to 8mm) depending on location on the CHL surface.
• Weight: ranging from 1.5 to 3.0 pounds per square foot depending on location, where such a solution will defeat a seventeen (17) grain fragmentation threat at a V50 velocity of up to 1950 fps.

The FRC design concept for a CHL creates a structure within a structure, i.e. a vessel within the aircraft cargo hold. Consequently, some interior volume will be lost based on the maximum thickness and dilational space claim of 12 mm and 13 mm, respectively (or roughly a 1 inch zone around the top and sides and a half inch zone along the floor) as measured inward from the fuselage stringers. The CHL (i.e. vessel) may dilate during explosive detonation without transmitting excessive loads into the aircraft fuselage that might otherwise impair airworthiness. Alternatively, soft shell (i.e. blanket type) liners are more compliant (i.e. flexible) and permit excessive deformation which results in greater load transfer to the aircraft fuselage, thereby increasing the risk of impaired airworthiness.

Compliance with FAA Requirements

The FRC CHL is Äre resistant and satisÄes all applicable FAA FAR 25 flammability requirements. The robustness and high damage tolerance of the FRC CHL design satisÄes all FAA Airworthiness CertiÄcation requirements.

BACK TO TOP