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personnel when there is a postcrash fire associated with an advanced composite aircraft. The health concerns
center around exposure to the fragmented composites and fibers which, are liberated as the resins burns off, and
may splinter in to particles that are small enough to be inhaled and retained in the lungs. Such health risks from a
single, acute exposures to combustion products of advanced composite materials are largely unknown. In recent
years, a number of incidents have been reported on the toxic effects of fibrous matter and aerosols on personnel
responding to the crash site [1]. Incident reports vary concerning the nature and severity of short- and long-term
adverse effects on the responding crews, ranging from eye and skin irritation to severe respiratory problems with
chronic post-exposure symptoms including forced breathing and reduced exercise capability. In certain instances,
response teams equipped with enhanced protective clothing have suffered from penetration by strands of needlesharp
carbon fibers resulting in infected wounds [2-4]. The burning of polymeric materials generates heat and
combustion products that consist of a complex mixture of gaseous and solid particulates from incomplete combustion,
collectively referred to as smoke. Combustion involves complex chemical/physical processes in which the
nature of products formed varies greatly with the composition of the material(s) and the burning conditions. The
composition and the concentration of combustion products are dependant upon ventilation i.e., the amount of
available oxygen and the resulting fire growth rate. At any stage of the fire development, the smoke stream contains
a mixture of evolved gases, vapors, and solid particles. Aerosols constitute the visible component of smoke and are
comprised of aggregates of solid particles mixed with combustion vapors and gases. Airborne particles vary widely
in size from submicron to many microns. Smaller particles stay suspended in air longer and are more likely to
adsorb chemical vapors from the smoke. The physiological effects of human exposure to fire effluent depend upon
the size distribution, solubility characteristics, and chemical composition of the aerosols, which determine the depth
of penetration in the lungs and the degree of absorption inside the body [5]. Firefighters are routinely exposed to
harsh and uncontrolled conditions, with partial products of combustion constituting the major source of chemical
exposure. They are frequently exposed to extremely high concentrations of a wide array of chemical and particulate
matter. There have been various studies on the health hazards posed to firefighters from various individual chemicals
in typical fire scenarios such as residential fires, industrial fires, and wildland forest fires. In a recent review,
Lees [6] has described the various chemical species, particulate matter, and their concentrations frequently encountered
by firefighters. However, little has been published describing the combustion products that are generated
from burning composites and the health hazards they might pose to the firefighting and rescue personnel. In view of
the current and projected use of composites in commercial aircraft, an extensive literature survey was undertaken
to determine what has been done by researchers to address the hazards related to composite materials. The
primary objective was to compile information on health effects caused by single acute exposure to various pollutants
including micron-sized fibers that become airborne during the burning and explosion in fiber composites on
impact. This study presents results of the literature review. The paper describes the general nature of hazards due
to fiber inhalation, and the potential hazards specific to particulate matter with associated chemicals released during
aircraft composite fires. Characteristics of fibers released from burning composites and their size distribution are
described. This review also examines some of the toxicological data available to assess the potential inhalation
hazard of carbon fibers.
POLYMER MATRIX COMPOSITES
Composites are generally classified according to their matrix phase. There are polymer matrix composites, ceramic
matrix composites, and metal matrix composites. These materials are commonly referred to as advanced composites
because they combine the properties of high strength and high stiffness, low weight, corrosion resistance, and
in some cases special electrical properties. The combination of such properties makes advanced composites very
attractive functional substitutes for metallic structural parts. The original impetus for development of advanced
composites was the performance improvement and weight savings for aerospace systems and military aircraft and
subsequently in the field of commercial aviation. Polymer matrix composites are very lightweight with a superior
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