Polycomposites were a type of material used in the construction of Federation starships.

In 2370, Data concurred with Jean-Luc Picard's suggestion that a previously unknown debris field located in the Hekaras Corridor was the Fleming, as it consisted mostly of duranium and polycomposite fragments. (TNG: "Force of Nature")

According to the Star Trek Encyclopedia (4th ed., vol. 2, p. 173), these were "synthetic materials".
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