Aerospace epoxy resins curing process

Aotlvatlon energy of flberlte epoxy, 141-43 Aerospace epoxy resins curing process, 127-29 density, 129,143 differential scanning calorimetry, 138-42... 

Phenohc resins (qv), once a popular matrix material for composite materials, have in recent years been superseded by polyesters and epoxies. Nevertheless, phenohc resins stiU find considerable use in appHcations where high temperature stabiHty and fire resistance are of paramount importance. Typical examples of the use of phenoHc resins in the marine industry include internal bulkheads, decks, and certain finishings. The curing process involves significant production of water, often resulting in the formation of voids within the volume of the material. Further, the fact that phenoHcs are prone to absorb water in humid or aqueous conditions somewhat limits their widespread appHcation. PhenoHc resins are also used as the adhesive in plywood, and phenohc molding compounds have wide use in household appliances and in the automotive, aerospace, and electrical industries (12). 

Loos and co-workers [11] have discussed the use of a carbon fibre uni-weave fabric with a tackifier coating as a potential replacement for tailored composite aerospace structures. The fibre was impregnated with epoxy resin and oven cured. Composite laminates that were fabricated using the modified process. These had higher mechanical properties than the composite laminates fabricated using a traditional process. 

The next major improvement in aerospace adhesives occured in the late 1950s with the introduction of adhesives based on epoxy resins. Since these adhesives crosslink via an addition reaction, no volatiles are released during heat cure. This made low pressure bonding possible and the use of nonperforated honeycomb feasible in sandwich structure. Other improvements followed that resulted in more durable bonded structure. These include the development of corrosion inhibiting adhesive primers in 1968, corrosion resistant aluminum honeycomb in 1969, and the phosphoric acid anodizing process for preparing aluminum for bonding in 1974. 

A 12rc cure epoxy with a 71 C dry service capability. A relatively short cure time and non-autoclave processing capability make this a versatile resin system. Typical applications range from commercial and sporting goods applications to helicopter and aerospace structures. 

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