| Carbon fiber woven mesh can effectively increase the strength of concrete.The randomly distributed chopped fiber increases the toughness and crack resistance of concrete.In order to improve the various properties of the concrete matrix,the two reinforced fibers can be combined and used.Because carbon fiber woven mesh and chopped fiber have different requirements for the composition and ratio of the concrete matrix,mixing them directly in the same concrete matrix may affect the performance of each fiber.In view of this,this project will layer composite Carbon Textile reinforced concrete(CTRC)and Engineered Cementition Composites(ECC)to form a new type of plate.The flexural properties of this kind of laminated composite plate are studied by three-point bending test.The test conditions are established by the material which is subjected to load in the composite plate and the thickness of each material layer.Present study obtains the following research results:(1)The effect of fiber length and cement strength grade on the tensile properties of ECC was studied.The results show that the influence of fiber length and cement strength grade on the properties of ECC materials is related.Only when the fiber length and cement strength match,can ECC materials with better strain hardening performance be obtained.(2)The basic mechanical properties of ECC and CTRC materials are studied,it was found that the ECC material has the characteristics of strain hardening and multiple slit cracking,and its ductility is high,but its compressive strength is poor.CTRC material has high tensile and flexural strength,but its ductility is worse than ECC,and the number of cracks in tensile test is low.(3)The study of three-point bending test of layered composite plate shows that when the mid-span load acts on the surface of the CTRC layer,the load-deflection curve shows a relatively gentle strain-hardening characteristic.The specimen has great flexibility and good toughness,and is characterized by multicrack steady-state cracking,many cracks and small width.The load-deflection curve shows a steeper strain-hardening characteristic when the cross load acts on the surface of the ECC material,the specimen has a high limit load,a small number of cracks and a large spacing,and a wide main crack.Compared with the same load position condition,the thicker the CTRC material layer is,the higher the flexural strength of the composite plate is,while the thicker the ECC material is,the better the ductility and toughness of the composite plate is.(4)The calculation formula of the cracking load of the layered composite plate was deduced theoretically,and the cracking resistance of the layered composite plate was calculated and analyzed.The calculation method of the flexural bearing capacity of the layered composite plate normal section under different failure modes was given.The theoretical analysis is in agreement with the experimental results.(5)The balance equation of the bending specimen of the reinforced ECC composite plate is deduced and compared with the calculated results of the CTRC-ECC laminated composite plate,the reinforced ECC composite plate has high flexural strength. |
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