In weaving, the warp (note spelling) threads run the length of the fabric and the weft (also called woof) threads are woven through the warp in a serpentine pattern. It's not possible to have a woven fabric without both warp and weft. The tensile strength of typical fabrics tends to be slightly higher along the warp direction. This might translate into better tensile strength for a composite.

The first point is discussed in

Z. A. Malik, M. H. Malik, T. Hussain and A. Tanwari, Predicting strength transfer efficiency of warp and weft yarns using adaptive neuro-fuzzy inference systems, Indian Journal of Fibre & Textile Research 35, 310-316 (2010).

The second is discussed in

S. Ramakrishna, Characterization and modeling of the tensile properties of plain weft-knit fabric-reinforced composites, Composites Science and Technology 57, 1-22 (1997).

In weaving, the warp (note spelling) threads run the length of the fabric and the weft (also called woof) threads are woven through the warp in a serpentine pattern. It's not possible to have a woven fabric without both warp and weft. The tensile strength of typical fabrics tends to be slightly higher along the warp direction. This might translate into better tensile strength for a composite.

The first point is discussed in

Z. A. Malik, M. H. Malik, T. Hussain and A. Tanwari, Predicting strength transfer efficiency of warp and weft yarns using adaptive neuro-fuzzy inference systems, Indian Journal of Fibre & Textile Research 35, 310-316 (2010).

The second is discussed in

S. Ramakrishna, Characterization and modeling of the tensile properties of plain weft-knit fabric-reinforced composites, Composites Science and Technology 57, 1-22 (1997).

Thank you David G Grier for the response ..

It seems your main interest lies in woven materials, but if you are also interested in knitted textiles the differences are much more pronounced, in aniostropy of mechanical properties (and tendency of weft knits to unravel but this is probaly not important when encapsulated in the matrix material)

Thanks Doen.. I am working on natural fiber composites

Hi Mr Bharat, 

Mr Grier answer regarding the typical fabric strenght is on the warp direction and that usually translate into better tensile strenght of the composite in warp direction and I agree with this general statement. Nevetheless, different fabric might have different parameters such as yarn size, yarn crimp, fabric density, cloth cover factor etc. Warp or weft? Several works I read come in the different results and it can be either warp or weft depends on the yarn size. The bigger the better, because the bigger yarn size means higher fibre content.  But then it depends on the twist factor given to fibres in spinning process. Another parameter that quite important is the cloth cover factor (ccf). Too high ccf value might end up with inappropriate adhesion between resin and fibre and too low will lessen the fibre contribution. So, it depends on the fabric parameter to determine which direction is better, warp or weft. The good of using natural fabric are control over fibre alignment and distribution beside of good handling during composite fabrication. Therefore, before composite fabrication, the parameter or propeties of the fabric should be determine in order to design the composite.

Just my 2 cents opinion

Thanks Mohd Iqbal Misnon

First, we have to ascertain that the fabric is balanced: i.e. equal number of tows of equal linear weight in both the warp (not wrap! ... parallel to the fabric length) and weft (across the fabric width) directions.  Then, we need to know the weaving prarmeters set on the loom (not trivial).  If we have very high warp tension, there will be high crimp in the weft so the fibres are mostly off axis and the fibre orientation distribution factor (used in the rules-of-mixture) is reduced and this is reflected in the composite properties.  At low warp tension, the crimp may be similar in both warp and weft.

Also, if making a large structure, the warp fibres are as long as the fabric roll, but the weft fibres are only as long as the fabric width so it may not be practical to have fuill fibre continuity.

Thanks alot John

Dear Bharath,

Warp or Weft direction of woven fabric depends up on the

direction of loading coming on the composite. For over all

strength of the composite both types of weaving are essential.

If the direction of loading is along the longitudanal direction,

perhaps warp may be better

Thank u Adachani Viswanathan Sethuraman

In woven fabric, normally the strength of warp yarn is higher than weft as warp yarns are stressed more during weaving. Again the number of warp threads per inch is also higher than weft in woven fabric. As a result woven fabric shows higher strength in warp direction than weft.  

I think warp direction is better due to more straightness and fiber density

One of the possible factor that affect the mechanical strength is the crimp level. High crimp level reduces the mechanical performance. Generally, warp crimp level is lower than weft crimp level. There are other woven pattern fabrics which reduce the crimp level to provide a better mechanical strength.