PSI - Issue 50

Alexander Eremin et al. / Procedia Structural Integrity 50 (2023) 65–72 Alexander Eremin / Structural Integrity Procedia 00 (2019) 000 – 000

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very high longitudinal elongation and transverse contraction of the specimen (Poisson ratio in such loading case is nearly 1). In the final periods to final breakage the deformation localizes in a narrow area.

ε yy

ε yy

γ 12 =1.3%

ε xx

ε yy

γ 12 =3.4%

ε xx

ε xx

ε yy

γ 12 =5.0%

ε xx

(a)

(b)

Fig. 1. Static tension of aramid fiber reinforced polymers with a [45 F ] 6S layup: (a) stress-strain diagram for 3 specimens; (b) fields of longitudinal ( ε yy ) and transversal ( ε xx ) strains.

Analyzing the deformation patterns and stress-strain curves, it was observed that a transition of linear to non linear behavior has different aspects in AFRP and CRFP. Due to higher ductility of aramid fibers, these fibers much more successfully distribute shear stresses. Thus, there have not been observed significant localization at 3.4% or 5.0% of strains. Carbon fiber composites demonstrate a fast increase in the strain localization and it is already observed at 3.4% and grows up to the failure. The authors believe that this is mostly attributed to the woven fabric rather than to the nature of the fibers. Non-linear behavior itself combines both fiber properties and fabric factor in distributing stresses.

ε yy

ε yy

γ 12 =1.3%

ε xx

ε yy

γ 12 =3.4%

ε xx

ε xx

ε yy

γ 12 =5.0%

ε xx

(a)

(b)

Fig. 2. Static tension of carbon fiber reinforced polymers with a [45 F ] 6S layup: (a) stress-strain diagram for 3 specimens; (b) fields of longitudinal (ε yy ) and transversal (ε xx ) strains.

Fig. 3 illustrates the behavior of aramid and carbon fiber composites at the much higher strain that implied by the ASTM standard. For AFRP the strain level in the images equals to τ 12 =40% and for CFRP – τ 12 =15%. So the strain