Simultaneous enhancement of axial/transverse compressive strength of aramid fibers by the construction of branched multi-hydrogen bonding sites

Abstract

The terrible compressive strength is a prominent issue that restricts the broad application of organic fibers in multi-dimensional stress scenarios. Traditional strategies focus on enhancing the axial compressive performance of fibers, simultaneously improving the axial and transverse compressive properties of fibers still poses significant challenges. Inspired by the octopus's tentacles that can conduct stress in multiple directions, a novel strategy by constructing branched multi-hydrogen bonding sites structure in aramid fiber was conducted to solve the problem. The branched multi-hydrogen bonding sites constructed on nano-silica (SiO2–B) offer excellent dispersibility within the poly(p-phenylene-benzimidazole-terephthalamide) (PBIA) matrix. Composite fibers (PBIA-SiO2-B) co-mixed with SiO2–B and PBIA were prepared using a solution spinning technique. The results of Fourier-transform infrared spectroscopy (FTIR) and dynamic mechanical analysis (DMA) reveal that the introduction of SiO2–B significantly enhances the intermolecular interactions within the composite fibers, and this enhancement mechanism has been elaborately elucidated through molecular simulations. Furthermore, finite element simulations confirmed that the incorporation of branched structure exhibits enhanced stress-bearing capabilities under multi-directional stress and offers outstanding support when subjected to transverse compressive stress compared to linear molecular chains. Hence, compressive property testing revealed that the PBIA-SiO2-B composite fibers achieved axial compressive strengths and transverse compressive strengths of 714.3 MPa and 305.8 MPa, respectively, representing increases of 68.8 % and 26.8 % over pure PBIA fibers. Moreover, with the enhancement of transverse compressive strength, the Young's modulus and interfacial shear strength of PBIA-SiO2-B fibers were also increased by 7.1 % and 20.9 %, respectively.