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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fields show the strain distribution in cases close to the final failure and can contribute to the understanding of nonlinear behavior and the process of deformation localization. The aramid fabric reinforced polymer has larger strains before fracture, as well as the narrowing of the middle section. High deformations of aramid fibers, woven fabric are the reasons for such behavior. Localization area is in the shape of a cross aligned at 45° to the vertical axis. Large x -axis deformation is easily observed due to shrinkage of the specimen in this direction. Carbon fiber reinforced polymers are stiffer, thus the strains are lower (~15%), shrinkage of the middle section is smaller and localization is not so pronounced. The strain fields visualized the deformation of a single thread of carbon fibers. Imperfect preload of reinforcement fibers during manufacturing makes some of thread underload while the others are loaded more uniformly. AFRP, γ 12 =40% CFRP, γ 12 =15%

ε xx

ε yy

ε xx

ε yy

(a)

(b)

Fig. 3. Fields of longitudinal ( ε yy ) and transversal ( ε xx ) strains for aramid and carbon fiber reinforced polymers at high strain.

It can be estimated that the fabric will better resist impacts, and can also be effectively used in composites with quasi-isotropic layup and in cases where it is important to achieve a more uniform distribution of material properties in different directions. 4.2. Tension of orthotropic and quasi-isotropic composites This section presents the results of tensile tests of aramid fabric reinforced composites with the [0 F ] 7S (orthotropic) and [45 F /0 F ] 3S (quasi-isotropic) layups, as well as carbon fiber reinforced composites with the [0/90] 5S and [45/0/-45/90] 2S layups. Stress-strain curves for all of them are presented in Fig. 4 , where ‘a’ is for aramid fabric composites; ‘b’ is for carbon fiber composites. Corresponding mechanical properties are shown in Table 2. Strain fields obtained by DIC are presented in Fig. 5.

a

b

Fig. 4. Stress-strain curves for tensile tests of (a) aramid fiber reinforced composites with [0 F ] 7S and [45 F /0 F ] 3S layups; (b) carbon fiber reinforced composites with [0/90] 5S and [45/0/-45/90] 2S layups.