Investigation On Fabrication And Properties Of Modified Lamellar Boron Nitride Reinforced Basalt Fiber/Epoxy Resin Composites

Over recent decades,the consciousness of environmental protection has been rooted in the people's minds.The use of fiber-reinforced epoxy resin composites,due to their excellent physical and mechanical properties,environmentally friendly and industrially competitive material cost,is nowadays widely spread in many engineering fields,with advanced technical applications in aerospace,architecture,military,transportation and automotive.When cured with hardeners,epoxy resin was brittle and has low resistance to crack propagation,easy to crack at low temperature environment.Moreover,the delamination damage in composite interlayer is the main failure mode for the laminated composites,which limits the application of materials.Therefore,we selected basalt fibers?BF?as reinforcements of epoxy resin composites,which have good low temperature resistance capability.And in this experiment,we selected Boron Nitride?BN?nanosheets as toughening agent,which were modified by the co-deposition of Dopamine?PDA?and Polyethyleneimine?PEI?.In this study,different molecular weight PEI modified BN were dispersed into epoxy resin via mechanical stirring to prepare the composites?EP/BN-PDA-PEI?,and their different behaviors in reinforcing epoxy composites were investigated.The obtained PDA/PEI-modified BN composites exhibited significant improvements in strength and toughness.When the PEI molecular weight at 10000,the tensile strength,fracture toughness and elongation at break of EP/BN-PDA-PEI-10000 composite increased by 51%,132% and170%,respectively from pure EP.In addition,the initial storage modulus of the epoxy composite increased by 1070 MPa compared with pure EP,the glass transition temperature?Tg?has no obvious change.At the same time,the temperature for 5%weight loss(T_-5%)was 51? greater than that of pure EP.During the research,diverse concentration solution of modified BN was sprayed on the surface of basalt fiber,and then the modified Boron Nitride-basalt fiber/epoxy resin composite laminates?EP-BF/mBN?were prepared by a hot-press process.The mechanical properties of the resulting composites at room temperature and low temperature?-60??were investigated.The results show that when modified Boron Nitride concentration was up to 6 g/L,the performance of the fiber-reinforced composite optimized.At room temperature,the bending strength and modulus of EP-BF/mBN-6 were increased from 745.4 MPa and32.3 GPa?EP-BF?to 850.4 MPa and 33.9 GPa,which increased by 14.9%and 5.0%,respectively;the interlaminar shear strength?ILSS?increased from 42.7 MPa to 58.5 MPa,which increased by 37.0%;the mode II interlaminar fracture toughness(G_IIC)increased from286.4 J·m^-2 to 464.8 J·m^-2,which increased by 62.3%.At-60?,the bending strength and modulus of EP-BF/mBN-6 reached 894.6 MPa and 34.6 Gpa,which were 19.2% and 4.5%higher than those of EP-BF;ILSS was increased from 43.5 MPa to 60.4 MPa,which increased by 38.9%;G_IIC was increased from 301.4 J·m^-2 to 483.9 J·m^-2,which increased by 60.6%.