| The composites reinforced by Poly-p-phenylenebenzobisoxazole(PBO) fibers have theadvantages of high strength and high modulus, which supply broad application prospects. Thus, tomeasure the structure and properties of the composites is important. At the same time, because ofsmoothness of PBO fibers, and no polar functional groups on PBO macromolecular chains, theinterfacial interaction between PBO fiber and matrix resin is not enough transfer stress. Therefore,how to improve the interfacial interaction becomes one of the most important research direction ofPBO fiber reinforced composites.In this paper, the PBO fiber/epoxy resin unidirectional composites and the fabric compositeswere prepared by different molding technology. The longitudinal tensile strength and modulus offiber-reinforced composites were studied. Simultaneously, the interfacial interaction between PBOfiber and epoxy resin was tested by surface-coating method.Firstly, epoxy618and the curing agent593were selected to build the composite system,further, the curing process parameters of this system was determined as follows: impregnatingstage was50℃/150min, the molding stage were preheat80℃/5min,80℃/0.3MPa/5min,80℃/2.5MPa/6min. Then, PBO fiber/epoxy unidirectional composites were manufactured byfilament winding molding technique. The tensile performance of these composites was measured.The results showed that the tensile strength and modulus of unidirectional composites were raisedfirstly and then decline with the increasing of PBO fiber content. Both properties reached to thetop at fiber content about56%, the tensile strength and modulus of the composites attained to1.44GPa and41.7GPa respectively. In addition, it was observed that the resin was debonded fromfiber surface by the SEM, which indicates that the interfacial interaction between fiber and epoxywas poor. The failure mode belongs to the interface failure, which fails to display the high strengthof the fiber.Secondly, in order to further improve the interfacial property of PBO fiber and resincomposite, two different coating agents, polyaramides and diethylenetriamine amine curing agent,were used to treat fiber surface. The changes in the chemical structure, surface morphology offiber surface and the interfacial shear strength (IFSS) between PBO fibers and epoxy resin werecharacterized to investigate the effects of the two coating agents on the surface properties of PBOfiber. Results showed that the modification effect of the curing agent on PBO fibers was better. Compared with the untreated fibers, the IFSS between the resin and the fiber treated withpolyaramides increased by70%, while turned to95%by treating with the curing agent. Thefailure mode transformed to the failure of the matrix and the fiber from the purely interfacialfracture.Finally, PBO/PA and PBO/EP composites were prepared from PBO fiber fabrics by differentmolding technology, the effects of the fabric layers on the fiber content was characterized.Preliminary studies have been carried out on the tensile strength, modulus and surface morphology.The results showed that while the number of PA films was certain, the fiber content decreased witha decrease in fabric layers. When the fiber content was about61%, the tensile strength andmodulus reached up to876.4MPa and44.0GPa respectively. In a certain thickness range(<1.5mm), increasing fabric layers made an increase of PBO fiber content in PBO/epoxycomposites, at the same time, improved the composites’ tensile strength and modulus. The failuremode of two kinds of fabric composites belong to the interfacial failure. Whereas, the formerdidn’t display the superior strength of PBO fibers in the composite, while the latter partlyexhibited the advantage from PBO fiber. |
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