Warp and weft are indications for the fabric direction. Warp is along the length as the fabric is unrolled, and weft is across its width: http://en.wikipedia.org/wiki/File:Warp_and_weft.jpg.

In composites you deal with warp and weft direction of fibers. The fabric that is produced can be impregnated with a resin (example an epoxy). The resin is the matrix.

I hope above makes clear that you cannot use matrix instead of epoxy warp. (it basically says nothing). You speak of fiber/yarn direction in combination of a matrix.

An example: the mechancal properties of a glass/epoxy composite in warp direction differ most of the time from properties in weft direction.

Warp is the lengthwise or longitudinal fiber in a oven fiber mat , while weft is the transverse fiber. Usage of warp matrix may not be correct.

Warp are longitudinal threads of a cloth (fabric) whereas the weft are the transverse threads. However in Textile and Engineering Composites language, the matrix is the resin or the binder material which holds the fibers/ yarns together and it's main purpose is to transfer the loading to the fibers/yarn.

It's usually in woven textile composites where you will find the terms warp and matrix. However there's no such thing as "warp matrix"

Warp is the yarn along fabric (reinforcement) length and matrix is a polymer.. The term warp matrix does not exist.