Appendix A
07/23/2010 AC 21 - 26A Appendix A APPENDIX 1. DEFINITIONS l. Adhesive. A substance capable of holding two materials together by surface attachment. Structural adhesives produce attachments capable of transmitting significant structural loads.
2. Article. A material, part, component, process, or appliance.
3. Chemical Characterization. A series of chemical examinations to identifY and/or quant if y the critical constituents of a material, and thereby establish a fingerprint of the material that can be used as a basis for future comparison.
4. Composite. A material containing two or more distinct materials (fillers, reinforcing materials, and compatible plastic resin) designed to exhibit specific performance properties.
5. Cur e. To change the physical properties of a material by chemical reaction, by the action of heat and catalysts, alone or in combination, with or without pressure.
6. Delamination. The separation oflayers in a laminate through failure of the matrix.
7. Fiber. A single homogeneous strand of material used as a principal constituent in advanced composite materials because of its high axial strength and modulus.
8. Filament. Fiber of extreme length, used in yams and other compositions.
9. Filament Winding. Process in which resin impregnated strands are applied over a rotating mandrel to produce high strength, reinforced cylindrical shapes.
10. Gelation. The formation of a gel, which is a jelly-like semi-solid material state formed by a network of so lid aggregates retaining a liquid phase.
11 . Hand layup. Method ofposit ioning successive layers of reinforcement material (which may or may not be perimpregnated with resin) on a mold by hand. Resin is used to impregnate or coat the reinforcement material. The resin is then cured to permanently fix the formed shape.
12 . Laminate. A product obtained by bonding together two or more laminae of the same material or of different materials.
13. Layup. A manufacturing process involving the placement of successive layers of materials. Also, the arranged set of laminae.
14. Matrix. The essentia ll y homogeneous material in which the fibers or filaments of a composite material are imbedded.
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Appendix A
07/23/2010 AC 21 - 26A Appendix A 15. Polymer. A high molecular weight organic material (natural or synthetic) formed by linking together a large number of repeating chemical units (monomers). When two or more monomers arc in volved, the product is called a copolymer.
16. Preimpregnated Material (Prepreg). A term generally used to describe fibrous material which has been preimpregnated with a liquid resin and cured to the B-stage.
17 . Production Approval Holder. The holder of a PC, PMA. or TSO authorization who controls the design and quality of a product or article(s). A person who has been issued a production approval by the FAA.
18. Pultrusion. A process by which continuous lengths oftiber are pulled through a pre-shaper of the desired cross-section and on through a heating source from which they emerge fully cured.
19 . Reinforcement Fibers. Materials such as roving, tow. and woven fabric used to produce a structural material superior to the base resin.
20. Resin. Any of the various solid or semi-solid amorphous natural or synthetic organic substances with indefinite and usually high molecular weights and no sharp melting point.
2 1. Sandwich Construction. A structural panel concept consisting in its simplest form of two relatively thin, parallel sheets (face sheets) of structural material bonded to, and separated by, a relatively thick, lightweight core.
22. Wet layup. A process in which dry fabric is laid into a mold and impregnated with liquid resin as part of the layup process.
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