Material A has a non-adhering interface with material B and is tested separately. Part of material B is within 13 mm of the occupant compartment air space, and materials B and C adhere at every point of contact; therefore, B and C are tested as a composite. The cut is in material C as shown, to make a specimen 13 mm thick.
B = 60 * (D/T)
Where:
B = Burn rate in millimeters per minute
D = Length the flame travels in millimeters, and
T = Time in seconds for the flame to travel D millimeters.
49 C.F.R. §571.302