Bamboo Like Porous Polyethersulfone Matrix Composite

Fiber reinforced polymer(FRP)has been widely used in aerospace,transportation,energy and chemical industry due to its high specific strength,high specific modulus,fatigue resistance and corrosion resistance.However,the brittleness of man-made fibers and the destructibility of resin matrix are always the core problems to be solved in the field of FRP: man-made highstrength fibers,such as glass fiber(GF)and carbon fiber(CF),are brittle materials,which are very sensitive to surface cracks and defects.A small number of surface cracks and tiny defects can lead to a sharp decline in the mechanical properties of fibers,and then the mechanical properties of FRP decrease.The toughness of epoxy resin,cyanate ester resin,phenolic resin and other thermosetting resin matrix is insufficient,which is also easy to cause fracture and interlaminar damage.Researchers usually repair the surface of the fiber to overcome the influence of surface cracks on the fiber,but this kind of method is expensive and difficult to large-scale application.And the problem of insufficient toughness of resin matrix can only be solved by complex toughening modification.However,in nature,bamboo,a kind of natural composite material with bamboo fiber as reinforcement and porous lignin as matrix,overcomes the disadvantage of insufficient toughness of lignin only by using gradient porous structure under limited material conditions,and has the characteristics of light weight,high strength and high toughness.Moreover,the local yield and fracture of porous lignin structure under load can also protect bamboo fiber,making bamboo show the strength that other natural materials can't match.The structural characteristics of bamboo inspired this study to use bamboo structure to prepare FRP with bamboo like structure,bamboo like porous polymer matrix can protect the structural characteristics of fiber by means of local yield,fracture and filling and repairing of fiber surface cracks,so as to overcome the influence of surface cracks on the mechanical properties of fiber and improve the toughness of composite.Therefore,polyethersulfone resin(PES)with excellent comprehensive properties and easily formed nano porous structure was used to prepare bamboo like composite materials by immersion precipitation phase transformation method,and the properties of bamboo like composite was been studied.1)Bamboo like porous polyethersulfone based monofilament fiber composites(GF/PES,CF/PES)were prepared by immersion precipitation phase inversion method.The PES matrix is a gradient porous structure.The tensile properties of GF/PES and CF/PES were higher than those of GF and CF,respectively.Through the study of Weibull distribution on tensile mechanical properties,it is found that the repair effect of porous matrix on the surface microcracks of fiber is the key factor to improve the mechanical properties of GF/PES and CF/PES.Moreover,GF/PES and CF/PES impregnated with phase change liquid have the characteristics of functional response due to the change of modulus of phase change liquid.2)Bamboo like porous polyethersulfone based laminar carbon fiber composites(LaminarCF/PES)were prepared by liquid-phase impregnation and immersion precipitation phase transformation.The low density of porous matrix and the local plastic deformation under external load not only help to improve the tensile mechanical properties of Laminar-CF/PES,but also make the specific strength and modulus of Laminar-CF/PES much higher than that of Laminar-CF/PES-Condense.In addition,the interface slip and the plastic deformation of porous matrix give the Laminar-CF/PES excellent energy absorption properties.3)Bamboo like epoxy resin/polyethersulfone based laminar carbon fiber composites(Laminar-CF/PES/EP)was prepared by liquid impregnation method.Epoxy resin(EP)filled the pores of porous PES matrix and formed the structure of porous framework wrapping EP matrix.The porous PES framework can not only improve the tensile mechanical properties of Laminar-CF/PES/EP by yielding and deforming under tensile load,but also absorb the energy of crack and hinder the crack propagation by virtue of its excellent plastic deformation ability,which can play the role of "anchoring" crack and effectively improve the fracture toughness of Laminar-CF/PES/EP.