Surface Treatment On Basalt Fiber And Its Composites Performance Evaluation

As a kind of advanced inorganic mineral fiber, basalt fiber has excellent mechanicalproperties, thermal stability, chemical resistance, no environmental pollution and a series of otherbenefits. So using it as reinforcement for fiber reinforced resin matrix composites has been widelyused in military industries and civil fields including aerospace, vehicle and ship building,architecture and agriculture. But basalt fiber has poor adhesion and wetting with matrix. In orderto give full play to excellent mechanical properties of basalt fiber, modifying on surface andimproving the interfacial adhesion condition has become a focus in composite science research．In this thesis, basalt fibers were treated by waterborne polyurethane solutions of differentconcentrations. The change of surface structure of basalt fibers was studied by SEM and IRtechnology, and the effects of surface treatment on mechanical properties of basalt/epoxy resincomposites were analyzed and estimated according to tensile test, bending test, impact test anddynamic mechanical analysis. Damage type and each stage of the characteristics were studied andassessed by acoustic emission signals; composite material fracture morphology and final failuremode was inspected by SEM.The results showed that through polyurethane treatment, obvious thin film and a few smallparticles were adhered on the surface of the fiber, cohesion between fibers was improved．ThroughFTIR technology, new polar functional groups appeared on surface, hydrogen bond formedbetween fiber surface and hydrophilic group in polyurethane solution.On this basis, basalt fabric was made composites by hand lay-up molding. The experimentfound that polyurethane treatment could improve mechanical property of composites. The tensilemodulus and strength of2.0wt%type was higher over31%and21%than0%type; the bendingmodulus and strength of1.0wt%type was higher over10.0%and6.9%than0%type; the impactstrength of3.0wt%type was higher over21.0%than0%type. From3.0wt%impact SEM,interface opening between fiber and resin slowed down and impact cross section appeared brittlefracture, which showed polyurethane treatment could effectively strengthen interfacial bonding.Through the analysis of the DMA, polyurethane also could produce flexible interface layerbetween fiber and resin, which reduced rigidity and storage modulus of materials. And also because of entangling between molecular chains, the movement of molecular chain segments waslimited. So loss modulus of materials was reduced. Besides that, glass transition temperature ofmaterials decreased. This showed polyurethane can increase viscosity, but decrease elasticity ofmaterialsWith the increase of polyurethane concentration, matrix cracking was delayed, observed onfinal failure mode. By acoustic emission signals, materials had a character of phases during tensileprocess. Especially, initial damage of0%type was occurred at50s, and then high energy signalsemerged, which meant part of the fiber breaking. But polyurethane could delay time of initialdamage and reduce the energy. Through different amplitude phase of AE counts and energypercentage, the highest tensile strength of composites, AE counts improved obviously and energyreached the highest above80dB. This showed fiber could have a good effect on carrying action.