Nonwoven and woven silk laminate composites
Properties of silk fibers
Many of the properties of silk fibers (as opposed to regenerated silks) also make them potential sustainable alternative reinforcement materials, alongside plant fibers, for engineering (i.e., nonbiomedical) composites. Table 6.2 compares the economic, technical and ecological properties of silks with plant and glass fibers. In general, the primary disadvantages of silks in comparison to plant and glass fibers are: (1) higher cost; (2) lower annual production; (3) higher moisture absorption; (4) lower softening (and therefore processing) temperatures; (5) poor stiffness; and (6) high embodied energy for processed materials (e.g., fabrics). However, they possess (1) lower density (than even plant fibers); (2) natural flame resistance; (3) moderate strength; (4) unparalleled toughness (higher than even Kevlar); and (5) a generally favorable environmental profile of the raw material. Other technical advantages of silks specific to composites applications include (1) their naturally continuous length; and (2) the high compactibility of silk preforms . While the former would translate to a high fiber length distribution factor and therefore reinforcing effect in composites, the latter provides an opportunity to produce high fiber volume fraction natural fiber composites .