| Nowadays,structural materials have trended to contain high strength in lightweight,and traditional materials cannot meet the high requirements of specific strength and specific modulus.But the composite material can obtain the performance that cannot be achieved by a single component through reasonable design and regulation between the components,and exhibits an unmatched advantage in this field.Among them,carbon nanocomposites represented by graphene and graphene oxide are ideal for new lightweight high-strength materials because of their large specific surface area,good processability and high performance.However,these carbon nanophases have problems such as difficulty in uniform dispersion and disordered arrangement in the resin,and the performance improvement of the composite material is much lower than the theoretical prediction value.The paper aims to solve the problem of dispersion and alignment of graphene oxide(GO)in resin,and explores the influence of aligned graphene oxide on the mechanical properties of composites and the enhancement mechanism.Because of good molding process and mechanical properties,this paper selects epoxy resin and bismaleimide resin(BMI)as the matrix.By constructing a three-dimensional framework of graphene oxide,the graphene oxide sheets are prevented from overlapping,and the agglomeration problem in the resin matrix is solved.Through mechanical tests of tension,three-point and compression,it was found that in each resin system graphene oxide has enhanced resin matrix.The low viscosity epoxy resin,TDE-85 epoxy resin and bismaleimide resin has reached the highest fracture strength with 0.3wt%,0.1wt% and 0.7wt% GO,respectively.And compared with pure resin,these fracture strengths increase by 24.7%,259% and 51.9%,respectively.Moreover,the introduction of graphene oxide also improved the thermal stability of bismaleimide resin,and compared with pure resin,the glass transition temperature and thermal decomposition temperature of composite material were respectively increased by 6.5 ° Cand 15 ° C.In order to use full of the mechanical strengthening effect of graphene oxide,this paper attempts to make the graphene oxide aligning in the resin.Thus,the paper explores and tries a variety of aligning solutions to improve the alignment,and finally finds a stable way to achive high degree of alignment and low defect,which makes the mechanical properties of aligned GO/BMI increase in most low GO blending ratios.Notably,the enhancement effect obtained by 0.1wt% GO/BMI was the most significant.Compared to 0.1wt% GO/BMI without aligning,the tensile and fracture strengths of 0.1wt% aligned GO/BMI increases by 76.4% and 22.9%;compared to pure BMI,it increases by 120.1% and 54.7%.Moreover,the SEM also show that the orientation and crack propagation trajectory of the GO extracted sheets after the aligning treatment show a certain trend.The paper also analyzes the enhancement mechanism of graphene oxide in bismaleimide resin and the effect of its alignment on the enhancement mechanism.It is found that the enhancement mechanism is mainly the layer extraction and interface solution.The pore growth around the reinforced phases prevents crack expansion and lamellar bridging,but the final enhancement effect depends on the alignment of graphene oxide.Especially,if the graphene oxide can align in perpendicular to the crack propagation plane,the mechanical properties will gain the greatest enhancement. |
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