广东纺织职业技术学院：《纺织材料学》课程教学资源（PPT课件，英文版）2 Fiber Properties and Indentification

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Chapter 8 Fiber Properties and ldentification

Chapter 8 Fiber Properties and Identification

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification a Mechanical properties ■ Tensile properties 口 Tensile deformation △l

Fiber Properties and Identification  Mechanical properties ◼ Tensile properties  Tensile deformation l 0 l f  l

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification a Tensile deformation: some concepts ■ Elongation A=1r- Strain △l 0 0

Fiber Properties and Identification  Tensile deformation: some concepts ◼ Elongation 0 l l l  = f − – Strain

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification □ Tensile deformation ■Load a Force applied to extend the fiber a Unfair to compare force applied to fibers with different sizes Stress Unit: Pa= N/m2 -Engineering stress F or dyne/cm2 G psi=pound/in 2

Fiber Properties and Identification  Tensile deformation ◼ Load:  Force applied to extend the fiber  Unfair to compare force applied to fibers with different sizes. – Stress –Engineering stress Unit: Pa = N/m2 or dyne/cm2 psi = pound/in2

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification □ Tensile deformation For textile yarns and fibers, hard to determine cross-section area use linear density gf/denier or N/tex

Fiber Properties and Identification  Tensile deformation ◼ For textile yarns and fibers, hard to determine cross-section area use linear density: gf/denier or N/tex

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification d Tensile testing of fibers ■ Testing conditions: ASTM standard for textile testing 70°F(21°C)and65% relative humidity(RH) Stress-strain curves 8

Fiber Properties and Identification  Tensile testing of fibers ◼ Testing conditions: ASTM standard for textile testing: 70°F (21°C) and 65% relative humidity (RH) ◼ Stress-strain curves   0

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification 口 Stress- strain curves ■ nitia|modu|us The slope of the first section of the stress-strain curve(ratio of the stress to strain) also called Young s modulus closely follows Hook's Law smaller modulus, easier to elongate under small stresses For different applications, different requirements ordinary apparels: high initial modulus women's sheer hosiery low initial modulus composites: extremely high initial modulus

Fiber Properties and Identification  Stress-strain curves ◼ Initial modulus The slope of the first section of the stress-strain curve (ratio of the stress to strain) also called Young’s modulus closely follows Hook’s Law smaller modulus, easier to elongate under small stresses. For different applications, different requirements: ordinary apparels: high initial modulus women’s sheer hosiery: low initial modulus composites: extremely high initial modulus

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification 口 Stress- strain curves ■ nitia|modu|us 0 8

Fiber Properties and Identification  Stress-strain curves ◼ Initial modulus   0

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification a Stress-strain curves ■ Yield point a The point at which the stress-strain curve flattens or changes its slope significantly Yield point Yield point

Fiber Properties and Identification  Stress-strain curves ◼ Yield point  The point at which the stress-strain curve flattens or changes its slope significantly   0 Yield point   0 Yield point

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Fiber Properties and Identification a Stress-strain curves ■ Yield point a The polymers yield or molecular chains start to move and pass one another a The deformation is permanent a The slope of the stress-strain curve after yield point relies on the strength of intermolecular forces flax due to strong intermolecular forces a Most fibers have yield point but not cotton and

Fiber Properties and Identification  Stress-strain curves ◼ Yield point  The polymers “yield” or molecular chains start to move and pass one another.  The deformation is permanent.  The slope of the stress-strain curve after yield point relies on the strength of intermolecular forces.  Most fibers have yield point but not cotton and flax due to strong intermolecular forces