Textile Structure
how cloth is put together
Concept

Tow — where it appears

A bundle of parallel filaments with no twist worth speaking of, delivered flat rather than round, whose width decides how closely it can be set. It is the reason a composite reinforcement is not simply a coarse yarn, and its flatness is what lets a preform reach a fibre fraction a round yarn could not.

Named by 3 essays across one field — each of them below, with the objects they name alongside it.

How much fibre a woven reinforcement holds. A unit cell of a woven reinforcement in section: flat tows, the thickness they add up to, and the wave the warp makes to cross them. The bar below is the fibre volume fraction against the same tows laid flat in two plies and against the packing factor of a tow, which is the most any cloth of them could be. The vertical scale is exaggerated so the interlacing is legible; the horizontal scale is the cloth's own.

The crimp is the price of being cloth

A woven reinforcement is bought for stiffness along its fibres, and the usual explanation of what it gives up — fibre content, lost to the crimp — has the sign wrong. At a given thickness a woven fabric holds slightly more fibre than two flat plies of the same tows. What the crimp costs is stiffness, and the float length is the knob.

applied · Preform A fabric to fill and a fabric to load. Fill time against the sett of a woven reinforcement, with the two limits a part imposes. Stiffness wants fibre, which wants a close sett; the resin has to arrive before it gels, and the channels between the tows — which is what carries the flow — close as the sett rises. The interval between the two is where a fabric can exist, and it narrows with the size of the part.

A fabric to fill and a fabric to load

A reinforcement has to hold as much fibre as possible and still let a resin through it, and the two demands are the same decision pulling opposite ways. Both bounds are computable, the interval between them narrows as the square of the part, and past a certain size it is empty — which is the most useful thing the arithmetic says.

applied · Preform Two sections, one yarn. The same yarn given a circular cross-section and a racetrack one of equal area, both jammed. The spacing the two models allow is nearly the same; the cover and the cloth thickness they predict are not.

A tow is not a yarn

Every geometric model on this site assumes a thread with a diameter. A reinforcement tow has a width and a thickness instead, and the two are eight to one — which moves the jammed sett, the crimp, the cover and the cloth's thickness at once, in four different directions, from one change.

applied · Sett

Named alongside it

The objects these essays reach for when they reach for this one.

CoverFibre volume fractionJammingPacking factorPreformCloth thicknessCrimpFloat lengthInfusionKnock-downPeirce's geometryPermeability

All concepts