Effect Of Braiding Angle On Mechanical Properties Of Basalt Fiber Composite Pipe Fittings

The fabric reinforced composite material is a novel composite material using a fiber woven fabric as a reinforcing material and a high molecular polymer as a matrix.Compared to laminate composites,fabric-reinforced composites and substrates are more tightly bonded,resulting in better structural integrity,higher specific strength,and higher levels of specific stiffness.However,the commonly used reinforcing fibers have the characteristics of high production cost,serious pollution,and difficulty in degradation,and the application of the fiber reinforced composite material in the civil field has been greatly restricted.Compared with other fibers,basalt fiber has three outstanding advantages:biodegradability,excellent mechanical properties and good economic value.Therefore,it is one of the best high-performance fibers with comprehensive cost performance.It can be applied to fabric reinforced composite materials,which can bring significant economic benefits to the society.In this paper,the basalt fiber fabric composite pipe fittings are studied,and the quasi-static compression performance and bending performance of the pipe fittings are studied.The effects of different braiding angles on the compression and bending properties of single-layer fabric composite pipe fittings were investigated.The three-dimensional model finite element simulation is used to predict the stress,strain,failure mechanism and failure mode of composite pipe fittings during compression,and compared with the test results,the failure mode of pipe fittings is analyzed.The main contents of the paper are as follows:(1)Sample preparation.The fabric weaving is woven by a 24-spin circular knitting machine.The basalt fiber is wound on the yarn barrel and woven in a circular knitting machine.By adjusting the winding speed of the motor and the rotating speed of the ring knitting machine,the fabric can be woven.Basalt fiber preforms of different woven structures.Basalt fiber reinforced composite pipe fittings were prepared by vacuum-assisted resin transfer molding(VARTM)process to form basalt fiber woven preforms with resin.According to the relevant standards of axial quasi-static compression and three-point bending test,the composite pipe fittings were respectively cut into samples of length 50mm and 130mm,and the mechanical properties of compression and bending were tested.(2)Modeling simulation.Based on the intersection method of curved surfaces,the simulation model of basalt fiber preforms is established.The spiral curve of the spiral surface and the extended surface is simulated to simulate the spiral trajectory of the fiber in the weaving process.The basalt fiber preforms are modeled by curve scanning and array.The established fiber fabric model was converted into a.step file and imported into Abaqus CAE for assembly analysis to define the material properties of basalt fiber and epoxy resin.Basalt fiber fabric reinforcement was defined as anisotropy according to the physical properties of the material tube components.And epoxy is defined as isotropic.At the same time,the direction is defined on the fiber braid to establish a local coordinate system of the material.The single cell model was used to predict the damage pattern of composite pipe fittings during axial compression and three-point bending.(3)Test.The prepared basalt fiber fabric composite pipe fittings were subjected to quasi-static compression and three-point bending test.In the axial quasi-static compression process,the test piece mainly produces four failure modes in the macroscopic direction:fracture,split and fold mode,in which the fracture and folding mainly occur in the real test piece with lower fiber content,and the collapse failure mode The test piece with high fiber content is mainly used.In the three-point bending test,as the load increases,cracks generated at the position of the indenter continuously extend toward the side wall of the pipe.The bending property of the pipe fitting is closely related to the braiding angle of the fiber preform,the braiding angle is increased,and the specific energy absorption value SEA,flexural modulus and bending strength of the pipe fitting are reduced,indicating that the bending property of the pipe fitting increases with the weaving angle.Large and reduced.Finally,the failure mechanism of the pipe fittings is analyzed by simulation,and the results of the tests are mutually verified.By comparing the mechanical performance curves,damage morphology and energy absorption characteristics between the two,the causal relationship between the braided angle parameters of composite pipe fittings and the failure mode is analyzed,and the correctness of the simulation model analysis is verified by experiments.