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and isocyanates. When a material burns carbon
monoxide,
TO 00-105E-9
3-26
carbon dioxide and water is formed along with products
of incomplete combustion. The chemical composition of
the material is used to predict possible incomplete combustion
products. If the material contains nitrogen, hydrogen
cyanide (HCN) and nitrogen dioxide are likely to
be generated. Nylon, polyurethane are two resins containing
nitrogen. Halogenated or flame retardant materials
produce the acid gases (HCl, HBr, HF). Aerospace
resins and adhesives are likely to contain halogenated
compounds. If oxygen is part of the chemical composition
of the material, acrolein and formaldehyde may form.
Polyesters, acrylics, epoxies and phenolic resins contain
oxygen. Isocyanates form from burning polyurethane
resins but the major fuel at an aircraft mishap is JP-8.
JP-8 will be the major contributor of toxic gases in the
smoke plume during a flaming composition state, see
Table 3.7-3.
(b) SMOLDERING. A smoldering condition for any material
produces harmful smoke. Carbon monoxide and
dioxide is formed along with products of incomplete combustion.
Many of the products produced are different from
a flaming combustion state because of the lower temperature
at which smoldering occurs. Harmful effects
occur if concentrations are high enough. Compared with
flaming combustion, smoldering is a slow process. Harmful
concentrations can occur if smoldering were allowed
to continue in a work environment, especially in an enclosed
space or environment.
(c) AIRBORNE CARBON FIBER. A significant fiber release
during a flaming combustion state will not occur for
a fire-damaged-only composite or for a composite made
entirely from a fabric or by filament winding. The potential
of a significant fiber release during a flaming combustion
state comes from a composite that was made
with many layers of carbon fiber unidirectional tape that
experience both physical then fire damage.
(d) HANDLING. Fire damaged composites are very
fragile, more fragile than just physically damaged composites.
Decomposed fibers will continue to break down
when handled; producing particulates. Handling burnt
(decomposed) carbon fiber may produce particulates from
the inhalable to the respirable size.
(e) STORAGE. Burnt composite may continue to offgas
for a period of time. Offgasing is a slow release of volatiles
at ambient temperatures. Due to buildup of concentrations
in a storage container, ventilation may be necessary
when the storage container is initially opened.
(6) SAFETY.
(a) SMOKE. The formation of acidic gases from resin
and plastic materials can create an acidic smoke plume.
Entering a plume may cause skin burns from acidic gas
penetration through the zipper or seam of the firefighter
suit.
(b) SMOLDERING. Smoldering composites are difficult
to extinguish with water. If the material is not entirely
cooled to ambient temperature, deep-seated smoldering
may continue to exist. A smoldering state can easily transition
to a flaming combustion condition. If smoldering
goes undetected, an unexpected fire can occur in the
work environment.
(c) CONFINED SPACE. Specific outdoor conditions
may present a “confined-space” scenario at a mishap
site. These conditions include thick vegetation, foliage
cover, deep impact crater, pool fire as well as lack of rain
and wind. Confined space increase the likelihood of hazard
exposures.
(7)MISHAP SITE MATERIAL COMPATIBILITY. A bulk
cured composite material is non-reactive, chemically and
biologically to the touch. A mishap may contaminate the
debris with aircraft fluids, melting metals, battery acid or
hydrazine. The compatibility of composite material with
other materials at the site is found in Table 3.7-3.
(8) MISHAP DAMAGED COMPOSITES SUMMARY.
·Coatings make it difficult to determine whether the underlying
part is a composite or metal.
· When damaged, the material within the “system” begins
to separate. It becomes apparent that the composite
part is not a homogenous material.
· Terms used to describe “mishap” composite:
o Single fiber
o Cluster
o Strip
o Dust, particulate
o Impact damage
o Fire damage
o Fiber bundle
· Impact damage:
o All fiber types break into shorter sections.
o Kevlar fibers create fibrils on the fractured surface.
o The solid matrix cracks and starts to pull away from
the fiber and the adjoining layers.
o Core material crushes and tears.
　
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