This white paper will outline the material and processes, which have been developed for the fabrication and application of an integrated composite firewall primary structure for use in military and commercial aircraft. Military and commercial aircraft have requirements to protect occupants from fire. One specific fire protection requirement is to contain a (1100°C/2000°F) flame for 15 minutes. This protection on composites is usually provided by a metallic firewall attached to the composite structure. The integrated ceramic composite firewall is an improvement over existing metallic firewall technology. This technology reduces cost, part count, weight, and manufacturing complexity of composites, which require fire protection.
The integrated ceramic composite firewall material and process incorporates ceramic fabric and film adhesive into one unique material. This new material is co-cured along with a parent laminate, creating a firewall that is integral to the composite primary structures of an aircraft. This new material and process have been tested for flame penetration per BSS7338 to meet the FAR 25 firewall requirements. The integrated ceramic composite firewall material has also been tested for stress and strain compatibility for integrated use in primary composite structures. This testing includes: filled-hole tension, open-hole tension, open-hole compression, and tension testing using various environmental conditionings. This testing shows that the co-cured ceramic firewall meets the FAR 25 requirement for flame penetration and also is strain compatible with composite primary structures.
The previous, firewall technology utilized individual metallic panels as a shield for fire penetration protection. This technology requires secondary bonding and mechanical fastening of the metallic panels to insure proper installation to the composite substructure. Some of the disadvantages are that the bond line between the metallic (Mil-T-9046) panels experience dis-bonding and allow fluids to migrate between the two surfaces, creating potential safety issues. Additionally, the use of metallic panels as fire protection increases not only the fabrication complexity and manufacturing flow time of an aircraft, but also contributes significantly to the overall cost and weight. The new material and process no longer require either of these two costly operations. The new process also completely eliminates the potential for ingress of fluids between the firewall and the composite laminate. The new material and process reduce the fabrication complexity by eliminating the need to cut, drill, bond, and fasten metallic sheets to the composite laminate. The new material and process allow the firewall to be co-cured into the composite laminate in a single operation, eliminating any and all subsequent operations experienced with the previous firewall technology.