Short for machine direction. Fibers and filaments tend to line up along it, so most nonwovens are stronger and stretch less in MD than in CD. The MD to CD tensile ratio is a quick fingerprint of the process: a parallel-laid card web can reach 10 to 1, while spunbond and cross-lapped needle felts sit much closer to balanced.
MD tensile is fine and CD is short, so we need more lapper layers, not more needling.
Always state the direction next to a strength number; an MD value quoted as plain tensile can make a weak fabric look strong.
Also heard as
- machine direction
- longitudinal direction
Do not mix it up with
- CD: CD runs across the roll width, at right angles to the machine direction.
Related terms
CD
Cross direction: the direction across the width of a nonwoven roll, at right angles to machine travel.
Grab tensile
Tensile test in which jaws narrower than the specimen grip its center, so neighboring fibers help carry the load.
Strip tensile
Tensile test in which the full width of a narrow strip is clamped and pulled to break.
Carding
Combing staple fibers between wire-covered rolls to open them and form an even, mostly parallel web.