Fiber Properties and ldentification Stress-strain curves Hardening point The polymer molecules 5A Hardening become more oriented as t strain increases and the fiber reaches a deformation limit where the molecules have the highest orientation and (stress)hardening occurs. 8
Fiber Properties and Identification • Stress-strain curves – Hardening point • The polymer molecules become more oriented as strain increases and the fiber reaches a deformation limit, where the molecules have the highest orientation and (stress) hardening occurs. 0 Hardening point
Fiber Properties and ldentification Stress-strain curves Failure point Where the fiber fails Sometimes not necessary the maximum stress point Depends on definition
Fiber Properties and Identification • Stress-strain curves – Failure point • Where the fiber fails. • Sometimes not necessary the maximum stress point. • Depends on definition
Fiber Properties and ldentification Stress-strain curves Tenacity Stress at the point of rupture Stress at the maximum load Unit: N/tex, gf/denier
Fiber Properties and Identification • Stress-strain curves – Tenacity • Stress at the point of rupture. • Stress at the maximum load. • Unit: N/tex, gf/denier
Fiber Properties and ldentification Stress-strain Stress at break or tenacity curves Strain or elongation at break of strain at the point of rupture Strain at the maximum load 8 Strain at break
Fiber Properties and Identification • Stress-strain curves – Strain or elongation at break • % of strain at the point of rupture. • Strain at the maximum load. 0 Strain at break Stress at break or tenacity
Fiber Properties and ldentification Stress-strain curves Work of rupture Physics: Work Force Distance FS If F=f( s) is not a constant >When change of distance As is very small, F is almost a constant, thus →)△v=F△sor when△s→>0,dh=fs)ds ->therefore dw=If(s)ds 0 0
Fiber Properties and Identification • Stress-strain curves – Work of rupture • Physics: Work = Force ´ Distance = F ´ s • If F = f(s) is not a constant →When change of distance s is very small, F is almost a constant, thus →w = F s or →when s → 0, dw = f(s)ds →therefore: = = l l W dw f s ds 0 0 ( )