preliminary secondary research

secondary research attempt no. 1, feat. textile physics

If there is one thing I've learned during my high school career, it's that not everything deserves a planning phase and a rough draft and an edited copy and a final version. The amount of documents I've handed in or presented with '1.0' tagged on the end or 'rough' tagged on the beginning is frankly disturbing. Given that this is a long-term project that I am expected to track, I'm just going to keep everything here. So yes, I am publishing a lot of unrefined, messy content, because waiting to format things is really just a recipe for procrastination, and time only compounds the list of things I need to do.

**I always use ?? for things I want to look into so that I can easily ctrl+f to find them; they're not necessarily all questions**

textile physics: physical properties of textile physics (Morton, 1963)

• some factors to consider:

  • fibre structure;

  • density;

  • moisture relations and effects;

  • mechanical, electrical, optical, and thermal properties; and

  • friction

physics of textiles (Treloar, 1977)

• link to pdf (also uploaded to drive)

• textile material properties

  • strength;

  • flexibility;

  • lightness

• undergarments

  • structure of low density

  • wool, cotton (relatively short fibres) produce open yarn structure

    • loose fibre ends and general irregularity (crimp) of filaments

• outer garments

  • important properties

    • resistance to tearing and abrasion

    • desirable draping and handling properties

    • resistance to creasing

    • stability of form (e.g. retention of pleats)

  • dependent on type of fabric structure and inherent properties of material

    • chemical properties of dyeing, laundering, and other processing

  • industrial yarns/fabrics: tire cords, conveyor belts, parachute materials, etc.

    • high impact strength and abrasion resistance

    • look into some of these for app??

• basic mechanical properties

  • production: assembly of fibres into the form of a yarn; geometrical interlocking of the yarn threads

    • carding: initial separation and randomization of the fibers

    • drafting: drawing together of the fiber into a loose roving of approximately aligned fibres

    • spinning: filaments are compacted to form a dense, coherent structure

  • strength: function of frictional forces between the helically conformed fibers

    • inter-fiber friction is required to maintain coherent structure

    • twist is essential even in continuous-filament yarns to prevent disruption by lateral forces

      • packing density of filaments is higher in continuous-filament yarns than short-filament (staple) yarns

        • staple yarns have more softness and warmth

        • many continuous-filament yarns are unsuitable for textile applications

        • texturizing processes are being developed for continuous-filament yarn

        • false twist: twist is introduced and set with heat, then untwisted (like I said earlier, look into felting??)

• mechanics of yarns and cords

  • maximum strain decreases progressively moving outwards

  • Hooke's law??

  • E_y=(E_f)cos^2(a_m)

    • E_y: modulus of the yarn

    • a_m: angle of outermost filament

    • E_f: modulus of the filament material

    • modulus decreases with increasing a_m (increasing twist)

      • tensile strength decreases with increasing twist??

      • discrepancies in this trend become more pronounced with increasing values of strain??

        • proposed reasoning: effects of transverse stresses, properties of material are not consistent with Hooke except at very small strains, changes in yarn diameter

        • J.W.S. Hearle??

        • stress-strain relations??

        • coaxial-helix model??

    • path of the filament is a helix of varying radius due to filament migration?? length of a filament increases with increasing distance from the yarn axis

      • in corded (plied) structures: strand will periodically disappear since each of the component plies must occupy the central or core position in the cord for some proportion of its length

      • if the rate of filament migration is relatively slow the properties of the yarn are negligibly affected

    • single yarns are mechanically unsymmetrical structures

      • torsional couple (??) can lead to snarling, etc.

      • multi-ply yarns are balanced due to initial and subsequent twist, so are typically used in systems subjected to high mechanical stresses

        • symmetrical cord structure

        • axis of each ply describes an identical helix about the axis of the cord

        • tortuosity: amont of twist

        • formation of the cord introduces additional tortuosity, but also impacts the length of the yarn axis

        • there is a large discrepency between theoretical and experimental values for three-ply cords, likely due to the distortion of the cross section of plies (mutual pressure in the contact region) which disturbs yarn geometry

  • fabric properties

    • mostly produced by weaving or knitting; both rely on geometrical constraints

      • felts and non-woven fabrics often lack flexibility due to high compression or adhesive bonding

      • factors to consider: tensile strength, abrasion resistance, extensibility, flexural rigidity, retension of creases, optical appearance, thermal transmission

    • plain-weave

      • governed by the two yarn diameters, the two thread spacings, and one of the two crimp angles

      • with load extension, removal of crimp in one direction is accompanied by an increase in crimp for those threads perpendicular

      • highly anisotropic system; for deformations in directions other than the thread directions, very different considerations apply

        • deformation occurs most readily in a 45 degree angle to the principal directions

    • creasing is related to the imperfect elasticity of fibers

  • fiber structure and properties

    • most textile fibers are partially crystalline organic polymers in which the molecules are preferentially aligned in a direction parallel to the fiber axis

    • on a weight basis, fibers are among the strongest materials known; a high-tenacity nylon filament has more than three times the strength of a steel wire of the same mass per unit length

    • the final properties of the fiber can be varied over a wide range by modifications of the spinning and drawing condition

      • higher degree of orientation achieved results in higher tensile strength lower extension to break

    • in industrial yarns, tensile strength is a primary objective; in textiles, high extensibility and lower modulus may be preferable

  • anisotropic properties

    • have greater strength in the direction of drawing than in the transverse direction

    • anisotropy arises from the disparity between the strong chemical bonds in the chain backbone structure of the molecule and the relatively weak van der Waals forces operating laterally between a given molecule and its neighbors

    • a difference amounting to a factor of about 50 would be expected between the longitudinal and transverse elastic moduli of a perfectly aligned system

      • not realized in a normal fiber as molecules are only imperfectly aligned

    • the tendency of highly drawn polymers to fibrillate is being exploited commercially for the production of the coarser grades of yarns and cords

  • fracture mechanics

    • mobility of the chain segments will decrease with decrease in temperature

  • application to fabrics

    • tear strength

    • marked increase in resistance to crack propagation can be achieved by the inclusion of crack barriers in the form of extra strong reinforcing yarns at regular intervals in the fabric structure

      • possible to raise the stress level from 35% to 82% of the static breaking stress for the uncut fabric

  • the textile industry is second only to the food industry when judged by the number of man-hours expended

    • important to factory operation, transportation system, conservation of energy, and clothing

    • not a lot of literature on this kind of stuff?? (come back and read this article later for review -- lots of interesting info)

tensile properties of textile material (textile physics - daffodil international university)

• tenacity: the ratio of load required to break the specimen and the linear density of that specimen

  • tenacity = load required to break the specimen / linear density of the specimen

  • measured in gm/denier, gm/Tex, N/Tex, CN/Tex, etc.

• breaking extension: the elongation necessary to break a textile material

  • breaking extension (%) = (elongation at break / initial length) * 100%

• work of rupture: the energy required to break a material or the total work done to break that material

  • measured in Joules

• initial modulus: the tangent of the angle between the initial curve and the horizontal axis is equal to the ratio of stress and strain

  • tan a = stress / strain

• work factor: the ratio between work of rupture and the product of breaking load and breaking elongation

  • work factor = work of rupture / (breaking load * breaking elongation)

• work recovery: the ratio between work returned during recovery and total work done in total extension

  • total extension = elastic extension + plastic extension

  • total work = work required for elastic extension + work required for plastic extension

• elastic recovery: the power of recovery from a given extension

  • depends on the type of extension, fiber structure, types of molecular bonding, and crystalline of fiber

  • total extension = elastic extension + plastic extension

  • elastic recovery (%) = (elastic extension/ total extension) * 100%

  • plastic recovery = (plastic extension / total extension) * 100%

• stress-strain curve: when fiber is deformed, it follows the stress-strain curve

  • linear region: follows Hooke's law; fiber returns to its original position after removal of load

    • elastic region

    • deformation is called elastic deformation

  • plastic region: the chain breaks but the fibers do not break

    • yield point: the point between the linear and plastic region

      • yield stress: stress at yield point

      • yield strain: strain at yield point

    • deformation is called plastic deformation

  • breaking point: the fiber breaks

    • breaking load: the load required to break a specimen

• creep: when a load is applied, an instantaneous strain occurs, but the strain will decrease with time

  • temporary creep: recoverable, textile material comes back to its original position after removal of load, elastic extension occurs, polymer chains slightly stretch

  • permanent creep: non-recoverable, textile material does not come back to its original position after removal of load, plastic extension occurs, polymer chains break

• tensile properties depend on the material and its condition (the chemical and mechanical treatment to which it has been subjected, the amount of moisture it contains, the temperature it is at), and the arrangement and dimension of the specimen

• methods of tensile experiment

  • constant rate of loading: uses container and water flow to increase load gradually; loading causes elongation

  • constant rate of elongation: uses a screw mechanism; elongation causes loading

yarn geometry

• ideal yarn:

  • circular in cross-section and uniform along its length

  • each fiber follows a uniform helical path around one of the concentric cylinder so that its distance from the yarn axis remains constant

  • a fiber at the center will follow a straight line of the axis (so assuming core spinning??)

  • number of filaments crossing the unit area is constant (constant density of packing)

  • every filament has the same amount of twist per unit length

  • consists of very large number of filaments

• yarn designation

  • yarn count

  • number of filaments

  • number of components in folding

  • direction and amount of twist (highly doubt z- vs. s-twist really makes a difference but maybe do one sample of comparison??)

  • number of components in cabling (could also experiment with cabled yarns?? this project has a ridiculous amount of planned samples at this point though)

  • fiber components

It is officially not Friday anymore, so I'm going to leave this here. It's given me a lot to think about, but I think I still have some more reading to do before doing any formal write-ups.