Continuous reinforcement fabric 537, bonding

Scrim A low cost reinforcing nonwoven fabric made from continuous filament yarn in an open-mesh construction. Used includes surfacing RPs to produce a smooth surface. Also used as a carrier of adhesives for use in secondary bonding of RPs, etc. 

Fabrication by Liquid Silicon Infiltration (reaction bonding) (LSI) A leading candidate for use in industrial gas turbine engine is a SiC matrix composite named toughened Silcomp [175]. It is produced by melt infiltration of molten silicon into a porous preform containing carbon as well as BN-coated SiC fibers (e.g. Textron SCS - 6). The composites thus produced consist of a fully dense matrix of SiC + Si, reinforced with continuous SiC fibers. Moreover, the melt infiltration process is net shape and fast. Ultimate strength and strain at ultimate strength are 220 MPa and 0.8 /o, respectively at room temperature (LSI-SiC/SiC Si). 

These adhesives offer the best short-term performance of any adhesives at elevated temperatures. PBI adhesives, however, oxidize very rapidly and are not recommended for continuous use at temperatures above 232°C. PB1 adhesives require a cure at 316°C. As with polyimide adhesives, release of volatiles during cure contributes to a porous adhesive bond. These adhesives are supplied as very stiff, glass-fabric-reinforced films and are very expensive. Their applications are limited by a long, high-temperature curing cycle. 

Continuous carbon fiber reinforced SiC composites were prepared by Xu and Zhang [211] using CVI, in which the preforms were fabricated by the three dimensional braid method. For the composites with no interfadal layer, flexural strength and fracture toughness increased with the density of the composites and the maximum values were 520 MPa and 16.5 MPam , respectively. The fracture behavior was dependent on the interfacial bonding between fiber /matrix and fiber bundle/bundle, which was determined by the density of the composites. Heat treatment had a significant influence on the mechanical properties and fracture behavior. The composites with pyrolysis interfacial layers exhibited characteristic fracture and relatively low strength (300 MPa). 

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