A composite structure manufactured on a knit stitch machine and including a pair of preformed substrates joined together by a knitted yarn system while being separated by portions of the yarn system. Preferably the yarn is bulked after knitting and defines a plurality of supports between the substrates. The composite is produced by feeding the substrates through a knit stitch machine, on opposite sides of a spacer bar and developing the knit stitches of the yarn system through and about the substrates while located on opposite sides of the spacer bar. After the composite is produced it preferably is subjected to heat to cause yarn of the yarn system to bulk and form supports between the substrates. The composites may be enclosed in sealed polymeric envelopes to form a cushioning pad, or may be used for filtration, insulation or other uses. The process of producing the composite and the spacer bar are also disclosed and claimed.