Basic Composite Repairs
Basic Composite Repairs
- The chemicals and cleaning agents used in laminating resins are hazardous substances and EXTREME CARE IS CALLED FOR WHEN HANDLING them.
- Most resins are SKIN IRRITANTS. Many people are ALLERGIC TO THE RESIN AND REPEATED SKIN CONTACT CAN CAUSE SERIOUS DAMAGE. If symptoms of an allergy appear when the resin is used, further contact should be avoided and the symptoms should slowly fade away.
- Direct skin contact with the resin should be avoided, and RUBBER OR PLASTIC GLOVES WORN when there is a possibility of the hands becoming contaminated.
- The resins and solvents, used with synthetic fibres, are ALL POISONOUS. Every precaution should be taken to KEEP THEM AWAY FROM FOOD. The FACE, ESPECIALLY THE EYES, SHOULD ALSO BE PROTECTED from resin and its solvents.
- If a rotary grinder is used on a glass fibre laminate, much glass and resin dust will be produced and a RESPIRATORY MASK SHOULD BE WORN for protection. The same dust is likely to cause an IRRITABLE SKIN RASH to develop on the forearms, especially when glass fibre is being hand-sanded.
- Before washing hands and arms, after working with GFRP, it is advisable to rinse them in cold water. The ARMS SHOULD BE WASHED IN SOAPY WATER and the operator should avoid scratching, especially while dust is lying on the skin.
Before commencing repairs on any composite material (whether it be a simple ‘fibreglass’ skin or a complex honeycomb sandwich), the complete area of the damage must be carefully surveyed. This must be done in accordance with the AMM, to ensure that ALL damage is discovered and assessed.
Any subsequent repair will depend on the type of damage, the extent of that damage and the importance (significance), to the safety of the aircraft, of the material being repaired. The AMM will provide either a repair scheme or component replacement information.
The strength of a glass fibre repair is dependent on the strength of the bond to the original structure. Since the repair receives its working loads through this bond, it is imperative that every effort is made to ensure a sound connection. Some of the important considerations are:
- Correct Surface Preparation
- Correct Bond Strength: This requires correct procedures to be used during the repair process
- Uniform Stress: Once again correct procedures during repair will ensure that local stress concentrations are minimised.