Learning Objective: Recognize the different safety precautions peculiar to working with advanced composites materials. 

The issue of personal health and safety is paramount when working with composite materials. With the rapid development of the new material systems, the full effect of hazards to personnel has not been determined; however, sensible shop practices and procedures have to be employed to prevent problems now and those that may appear later. Following these safety precautions may prevent future health problems, such as those encountered in the case of asbestos fibers.

Airborne dust and fibrous particles are the principal source of hazards. These particles are generated by drilling, sanding, routing, or sawing the composite structures. Fine, lightweight fiber particles are easily circulated into the atmosphere, causing skin irritation and inflammation, eye irritation, respiratory system inflammation, pulmonary diseases (black lung), cancer of the lung, and abdominal disorders. Respiratory protection is required in those operations where dust exists or is generated. Eye protection, consisting of safety goggles or a face shield, is also recommended for use in work involving any operation where the likelihood of airborne fibers exist. Broken fibers can penetrate the skin. The fibers may become lodged beneath the skin. These fibers are so brittle and difficult to remove that they generally have to be cut out and the wound disinfected to prevent infections.

Personal hygiene includes washing your hands before and after working with composites, and your hair should be washed at the end of each day. Wash dust-contaminated clothing separate from other clothing. Do not eat, drink, or smoke in the composite repair area.

Graphite dust and particles are conductors and can cause shorts in electrical motors and avionics circuity. Also, these dust particles can affect the aircrafts fluid systems. In the hydraulic system where contamination is critical, actuating cylinder rods can draw the dust particles into the system, causing premature seal failures. The abrasiveness of these dust particles can also cause failures to valves, pumps, and other close tolerance parts. In the fuel system, these particles can be introduced during wet wing repairs, causing clogged filters and erroneous readings in capacitance fuel quantity probes. The abrasiveness of these dust particles can cause failures to fuel controls and other close tolerance fuel valves.

Because of the necessity to use solvents while accomplishing bonded repairs, potential health and fire dangers must be given special consideration. Solvents dissolve natural skin oils and result in drying and cracking of the skin, rendering it susceptible to infection. Additionally, these solvents may cause irritation and allergic reactions to individuals. If the vapors are inhaled during prolonged and repeated exposure to moderate concentrations, solvents can cause headache, fatigue, nausea, or visual and mental disturbances. Extreme exposure may result in unconsciousness and even death. Solvent vapors may also act as an anesthetic or cause irritation of the eyes or respiratory system. In addition, they can result in blood, liver, and kidney damage. Therefore, adequate ventilation should be provided during mixing and use of adhesives, solvents, and cleaning solvents.

To minimize or eliminate the danger of tire and subsequent destruction of life and property, flammable solvents should be used only in approved areas and with methods recommended by local fire safety authorities. Composite material fire hazards are usually limited to solvents and resins. Flashpoints of solvents and resins vary, but are usually around 200F or above. High-temperature resins have higher flashpoints. Burning composite surface temperatures can exceed 1,000 to 1,400F and generate high internal combustion temperatures (830F and above). Burning composites liberate dense smoke-drawing particles into the air, presenting hazards to personnel. Besides being hazardous to personnel, dust affects the quality of repairs. Bonding repairs will not be performed in the same area as machining operations. Vacuuming is used during all machining operations. Some of the fire prevention and suppression requirements are as follows:

1. Eliminate all flames, smoking, sparks, and other sources of ignition from areas where solvents are used.

4. Solvents should be used in approved ways and stored in approved containers.

5. Ensure adequate ventilation where vapors are present.

6. Ensure aircraft and equipment are static grounded.

7. Composite materials produce hot fires. Combat fires with chemical foam, dry chemicals, CO2, or low-velocity water fog.

9. Wear self-contained breathing apparatus when fighting fires.

WASTE DISPOSAL 

Carbon or graphite fibers cannot be disposed of by incineration. All composite material particles and dust must be packaged, tagged, and buried in an approved landfill. Do not allow fibers to contaminate water supplies.

Coolants used in machining composites also contain fibers and particles. When disposing of these particles, allow them to remain still so they will settle to the bottom, drain off the liquid without disturbing the particles, and then bag and dispose of them properly.