Abstract
High-performance fiber-reinforced composites (FRCs) are widely used in bulletproof structures, in which the mechanical properties of the single fibers play a crucial role in ballistic resistance. In this paper, the quasi-static and dynamic mechanical properties of three commonly used fibers, single aramid III, polyimide (PI), and poly-p-phenylenebenzobisoxazole (PBO) fibers are measured by a small-scale tensile testing machine and mini-split Hopkinson tension bar (mini-SHTB), respectively. The results show that the PBO fiber is superior to the other two fibers in terms of strength and elongation. Both the PBO and aramid III fibers exhibit an obvious strain-rate strengthening effect, while the tensile strength of the PI fiber increases initially, then decreases with the increase in strain rate. In addition, the PBO and aramid III fibers show ductile-to-brittle transition with increasing strain rate, and the PI fiber possesses plasticity in the employed strain rate range. Under a high strain rate, a noticeable radial splitting and fibrillation is observed for the PBO fiber, which can explain the strain-rate strengthening effect. Moreover, the large dispersion of the strength at the same strain rate is observed for all the single fibers, and it increases with increasing strain rate, which can be ascribed to the defects in the fibers. Considering the effect of strain rate, only the PBO fiber follows the Weibull distribution, suggesting that the hypothesis of Weibull distribution for single fibers needs to be revisited.
Highlights
High-performance fibers are widely used in aerospace engineering [1], civil construction [2], marine engineering [3], electron components [4], and biomedicine [5] due to their superior mechanical properties such as high specific strength and modulus
The results showed that the strength of a single carbon nanotube (CNT) fiber increases as the strain rate increases, while there is no noticeable strain rate effect for polyacrylonitrile-based carbon fiber
The quasi-static and dynamic mechanical properties of three high-performance single fibers were measured by a tensile testing machine and an improved mini-split Hopkinson tension bar (SHTB), respectively
Summary
High-performance fibers are widely used in aerospace engineering [1], civil construction [2], marine engineering [3], electron components [4], and biomedicine [5] due to their superior mechanical properties such as high specific strength and modulus. PI fiber is composed of a large number of rigid conjugated structures such as imide rings and aromatic heterocyclic rings. This unique chemical structure possesses large bond energy, and considerably improves the intermolecular force between the macromolecular chains through π-π interaction, rendering materials with good mechanical properties [8]. According to previous reports [9,10], the tensile strength of domestic PI fiber can reach 3.5 GPa and the modulus exceeds 140 GPa. PBO fiber is one of the most promising members of the polyamide family containing heterocyclic aromatics, and is known as the super fiber of the 21st century
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