ABSTRACT:A new type of polyimide/silica (PI/SiO 2 ) hybrid composite films was prepared by blending polymermodified colloidal silica with the semiflexible polyimide. Polyimide was solution-imidized at higher temperature than the glass transition temperature (T g ) using 3,3Ј,4,4Ј-biphenyltetracarboxylic dianhydride (BPDA) and 4,4Ј-diaminodiphenyl ether (ODA). The morphological observation on the prepared hybrid films by scanning electron microscopy (SEM) pointed to the existence of miscible organicinorganic phase, which resulted in improved mechanical properties compared with pure PI. The incorporation of the silica structures in the PI matrix also increased both T g and thermal stability of the resulting films.
ABSTRACT:The anionic graft copolymerization of e-caprolactam onto a Kevlar-49 fiber surface was carried out by using a metalation reaction in a dimethyl sulfoxide solution of sodium hydride. The effects of reaction conditions on the graft yield and on the tensile strength of the fiber have been investigated. Graft yield significantly increased with increasing metalation time, NaH concentration, and monomer concentration. The graft yield varied from 6 to 32% with reaction conditions. The tensile strength of the fiber depended predominantly on NaH concentration. The retained tensile strength was over 93% when the concentration of NaH was below 2.1 mmol/L per 0.5 g of Kevlar.The discontinuous Kevlar fiber reinforced composites were prepared by a blending/ melt-pressing method. In thermomechanical and dynamic mechanical analyses, the relaxation peak of grafted Kevlar fiber/Nylon 6 composite film moved to higher temperatures, compared with the original Kevlar fiber/Nylon 6 composite film. The grafted Kevlar fiber reinforced Nylon 6 composite film exhibited mechanical properties superior to those of the original Kevlar fiber reinforced composite film. The higher thermal and mechanical properties were due to the effect of higher interfacial interaction between the grafted Kevlar fiber and matrix.
During the manufacture of specialty yams by blending dyed cotton and raw cotton, fibers damaged by the dyeing process degrade the physical properties of the specialty yams. For a raw cotton blended with a large amount of dyed cotton, the spinnability of the specialty yarn worsens due to the disparity of the raw materials, which makes fine count specialty yarns. difficult to manufacture. The basic properties of the component fibers of a specialty yarn, such as strength, elongation, unevenness, and spinnability, are analyzed as a function of the blending ratio of the dyed cotton to provide reference properties for fine count specialty yams.
Recently, carbon fiber reinforced plastic (CFRP) with high strength, stiffness, and lightweight is used widely in number of composite applications such as commercial aircraft, transportation, machinery, and sports equipment. Especially, it is necessary to apply lightweight materials to car components for reducing energy consumption and CO2 emissions. In case of car roof reinforcement manufactured using CFRP, superior strength and bending stiffness are required for the safety of drivers in the rollover accident. Mechanical properties of CFRP laminates are generally dependent on the stacking sequence. Therefore, research of stacking sequence using CFRP prepreg is required for superior bending stiffness. In this study, the 3-point bending FE-analysis for predicting the bending stiffness of CFRP roof reinforcement was carried out on three cases [Formula: see text], [Formula: see text], and [Formula: see text]. Material properties that the six independent elastic constants are E11, E22, G12, G23, G13, and ν12 used in FE-analysis were evaluated by the tensile test in 0°, 45°, and 90° directions. Through structural strength analysis of the automobile roof reinforcement fabricated using CFRP, the effect of the stacking sequence on the bending stiffness was evaluated and validated through experiments under the same conditions as the analysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.