Abstract: Beams commonly fail in shear due to diagonal tension, shear compression, or web shear, typically caused by insufficient reinforcement, overload, or material weaknesses. One solution is the use of fiber-reinforced polymer (FRP) wrapping, which enhances durability and strength. FRP, a composite of fibers and resin, exhibits superior mechanical properties such as impact resistance, stiffness, and corrosion resistance. This study investigates the effectiveness of Polypropylene Fiber Reinforced Polymer (PFRP) in strengthening reinforced concrete (RC) beams. Mechanical behaviour was assessed through compression, split tensile, and flexural tests. RC beams wrapped with PFRP were also analyzed in terms of shear strength using experimental and simulation methods. The results indicate higher strength in PFRP-wrapped beams compared to unwrapped ones.

Abstract: In this study, the change in the entanglement state of entangled polyethylene (PE) melts was induced by cyclic deformation, i.e., a continuous orientation–relaxation process. The change in density fluctuation during the cyclic deformation process of ultrahigh-molecular-weight linear low-density PE (UHMW-LLDPE) melts was evaluated using in situ small-angle X-ray scattering (SAXS) measurements. Significant differences in scattering anisotropy were observed between the UHMW-LLDPE films polymerized using metallocene and Ziegler catalyst systems. For the metallocene film, the density fluctuation developed gradually in the deformation direction and was maintained via orientation/relaxation during the cyclic deformation. In contrast, for the Ziegler film, which contained a large amount of loosely entangled chains with higher mobility, the density fluctuation rapidly increased and stabilized. The scattering was constantly isotropic, and the isotropic scattering was maintained throughout the cyclic deformation. Thus, cyclic deformation stabilized the molecular entanglement of entangled PE melts based on the intrinsic relaxation time of each entanglement.

Abstract: Effect of water and organic solvents on dynamic viscoelasticity of cellulose triacetate fiber (CTA_f) was studied comparing with that of regenerated cellulose fibers such as rayon, cupra and lyocell. The peak of the mechanical loss tangent (tan δ: ratio of the storage modulus to loss modulus of viscoelastic materials) was observed during drying process of wet CTA_f indicating that glass transition temperature of 193°C in dry state decreased to room temperature in wet state. The same phenomenon has been observed for regenerated cellulose fibers; however, the height of the tan δ peak (tan δ_max) for CTA_f was lower than those of regenerated cellulose fibers. Tan δ_max qualitatively indicates the size of the moving unit suggesting smaller size of the moving unit affected by water for CTA_f than those of regenerated cellulose fibers despite quite low crystallnity of CTA_f. Organic solvents including both polar and nonpolar solvents induced glass transition for CTA_f. n-alkane with relatively large molecular weight, n-nonane and n-decane, also caused glass transition at room temperature for CTA_f not for regenerated cellulose fibers.