| Basalt fiber(BF)has a good mechanical performance,water resistance,weather resistance and corrosion resistance and so on,which has been widely used in the construction,road transport and bridge engineering field.However,there are few reports on composite prepared BF with plant fiber.SO it's creative for studying the composite prepared new-type BF with plant fibers.Flax fiber and BF reinforced unsaturated polyester(UP)composites were prepared by compression molding in this research.The mechanical properties of flax fibers reinforced UP composites were improved by chemical modification,introduction of inorganic fibers and plasma treatment in this paper.Firstly,Alkali treatment and silane coupling agent(G-570)affected on various performance of flax fiber and flax/UP composites.And then hybrid composites were fabricated by BF,flax fiber and UP and changed in mechanical properties,weather resistant and water absorption and so on of hybrid composites as a function of BF contents.At the same time,the mechanism of degradation of hybrid composites was discussed.Effects of plasma modification for fibers on the mechanical properties of hybrid composites were investigated.The dynamic mechanical behavior and interface of the hybrid composites was investigated using DMA,XPS and SEM were used to characterize the surface chemistry of the fibers and the interfacial adhesion of the composites,respectively.The results of research are as follows:(1)The tensile strength and flexural strength of composites which were treated by alkali concentration(0%?11%)and 2%G-570 were improved,but impact strength decreased.Composites treated with alkali concentration(3%)and 2%G-570 that had the best mechanical properties.Compared with the unmodified composites,the tensile strength and flexural strength of modified composites were improved 36.7%and 48.5%,respectively.The results of DMA indicated that the storage modulus of modified composites(3%alkali and 2%G-570)reach maximum and the impact strength of modified composites decrease because of better rigidity and brittleness.The thermodynamic property of modified composites were improved,because the Tg values of modified composites was 15.2? higher than unmodified composites.The results of SEM demonstrated that most of fibers are pull off in modified composites and debonding and void appear at the unmodified composites.And more,the interfacial adhesive is superior between modified fibers and UP.Chemical bonding mechanism indicated that the main backbone and branch increase due to the formation of covalent bonds using G-570 between flax fibers and UP.So the mechanical property and thermo-stability of composites were improved by the modified method.(2)Basalt fiber fabric and flax fiber fabric were used as materials to fabricate hybrid composite materials using the hybrid design of sandwich and interlayer cross,and the performances of the hybrid composite materials were analyzed.Results showed that the overall mechanical properties of hybrid composite materials was strengthened better when the skin layer was basalt fiber fabric and the sandwich layer was flax fiber fabric,and this hybrid design was decided to be used to make hybrid composite materials.With the increase of BF content,the theoretical density of BF/FF/UP decreased versus the actual density increased,and the flexural property and flexural strength of BF/FF/UP were also strengthened simultaneously.The flexural strength,flexural modulus and impact strength of B3 were 40.7%,64.5%and 39.4%higher than that of,B1,respectively.Mass ratio of FF/BF affected water diffusion behavior.With the increase of BF content,water absorption of hybrid composite materials significantly decreased,which did not comform to Fickian diffusion.The results of DMA tests indicated that the E' of BF/FF/UP increased with the increase of BF,the E' of B3 improved 75.5%in comparison with UP,and modulus variation of B3was significantly lower than B1 and B2.The value of E"?Tg?tan? peak and Ea showed that with the increase of BF content,E",Tg and Ea increased gradually,while tan? peak decreased.It meant that the surface energy was correlated with strength and content of reinforcement in hybrid composite materials.The results of SEM indicated that crack appeared between flax fiber and UP was bigger and the interfacial adhesion was superior between BF and UP.(3)Chang in weather resistant of BF/FF/UP as a function mass ration on flax fiber fabric and basalt fiber fabric were studied.The results of research demonstrated that the flexural strength,flexural modulus and impact strength of BF/FF/UP firstly increased and then decrease the increase with aging time.Comparing with maximum flexural strength value,the minimum value decreased by 37.5%,41.9%and 43%,B1,B2 and B3,respectively.With regard to impact strength,the figures were 33.2%s 33.3%and 46.8.The results of ANOVA and LSD illustrated that ultraviolet aging time had significant effects on flexural strength of B3,while basalt fibers contents had non-significant effects on flexural strength retention.The results of DMA showed that the storage modulus of B3 firstly increased and then decreased with increase of the aging time.The results of reason may be part of UP continued to cross-linking solidify and degradation at the same time as the increase of aging time.The loss factor peak of BF/FF/UP increased and the interfacial adhesion started to get worse after aging 360 h.So the mechanical property of hybrid composite was decreased due to the degradation of UP leading to appear crack and expansion between fibers and UP.The mechanism of ultraviolet degradation for UP showed that ester group,free radical and low molecule compound such as CO,CO2 and so on may be produced and the backbone of polymer breakage.The result of FTIR indicated that carbonyl group,ester group and characteristic peak of UP weaken and benzene ring vibration peak disappear for the aging composites.The relative content of oxygen elements decreased whereas that of O-C=O and C-O increased.The conclusion is the same as previous result.The water absorption performance of composites was significantly affected by aging time.After aging 600 h,the water absorption of composites(B1,B2 and B3)increased by 39.1%,44.9%and 50.3%,respectively,compared with that of un-aged composites.The reason of results may be that the degradation of UP would be result in the crack of interface and improve the water absorption performance for the flax fibers.Moreover,hydrogen bond of fibers surface would be further destroy the interface between flax fibers and UP and appear much more void.The phenomenon such as debonding,void was appeared by SEM.It was concluded that water have an effect on interfacial failure.(4)Hybrid composite materials(BF/FF,PBF/FF,PBF/PFF and BF/PFF)were prepared with basalt fiber fabric and flax fiber fabric which were treated with oxygen plasma at low temperature.Results indicated that the surface of fibers appeared rough and corrosion after the treatment The results of SEM and XPS on the two material after low temperature showed that four function group(-C-OH,-C-O,-COOH and-COO-)appeared on the surface of flax fiber fabric,while the crystal structure of basalt fiber fabric changed into[SiO4]4-tetrahedron,[Si2O5]2-layer and[S2O6]4-chain.The flexural and impact performance of hybrid composites were significantly improved by plasma treated with fibers.The flexural strength of BF/PFF was 40.5%higher than that of BF/FF and the impact strength of PBF/PFF or BF/PFF is 116%higher than that of BF/FF.The results of SEM showed that the interfacial adhesion is better between modified fibers and UP.The results of DMA indicated that the storage modulus of PB/PF have the top values and is 21.3%higher than that of BF/FF.Modified fibers have superior interfacial by plasma and the results are the same as previous analysis. |
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