چكيده به لاتين
In many fiber-reinforced polymer-based composites, the interphase between matrix and fiber, despite its insignificant size, has a major effect on composite’s properties. in fact it is glass-fiber sizing (produced during fiber production procedure) ,that forms this interphase. In other words, fiber sizing, forms a bound between hydrophobic surface of polymer matrix and hydrophilic surface of glass-fiber. this conduct is a suitable media for transferring loads from matrix to fibers. In this study, sizing as an industrial product is identified and a practical method of production is provided further. On next step, due to surface roughness change, sizing effect on a composite laminate has been studied. In order to do so, unsized fibers are made by heat treated glass-fibers. at this step, fibers similar to the residual ones from recycled composites, are provided. then heat treated fibers are resized with dipcoating in sizing pool. therefore virgin fibers, unsized fibers and resized fibers are three available sets. samples are made by using above fibers and hand lay up method in order to form composite laminates. Then composite laminates were subjected to tests such as transverse tensile test, three point bending test, in plane shear test and interlaminar fracture toughness mode I. results show a significant reduction in material properties of unsized fibers In comparison with virgin fibers. results also show that resized fibers have almost the same mechanical properties as virgin fibers. Meaning that, unsized glass fibers remaining from recycled composites can be reused by applying the method mentioned in this thesis. for the next step of this study, in order to reinforce the interphase, using nano particles CNT, CNF and nano-silica, is suggested and then studied. Enhancing fiber surface roughness, leading to a higher mechanical interlock and friction between fiber and matrix, is investigated and its effect on composite’s mechanical behavior is observed. in contradiction with previous studies, in this thesis, nano particles are used in the interphase of fibers and resin, rather than matrix. For this purpose, fibers should be coated with mentioned particles, so that the particles stay in the interphase region. for this purpose, nano particles are dissipated carefully in sizing material by a Ultrasonic method. Next, heat treated virgin fibers will be coated with nano modified sizing. then composite laminates are produced by current fibers and they will be tested, consequently. test results show 18% improvement on transverse tensile strength of composite laminates, due to presence of nano carbon particles (CNF) in glass fiber sizing, in comparison with virgin fibers. also sizings which are reinforced by carbon nano tubes (CNT), show increase in strength in all test cases. for instance, there has been a 30% improvement in transverse tensile strength for a CNT reinforced sizing fiber in comparison with virgin fibers. Among the samples, nano-silica reinforced sizing fibers, showed the highest effect on strength of composite laminates .for example, nearly 50% improvement on shear strength of a composite laminates using nano-silica modified sizing fibers resulted in comparison with virgin glass fibers. Also In this study introduce an innovative method of using nano-silica modified sizing, as an industrial plan.
