| Processing solid buoyancy materials are usually refers to hollow glass bead(HGMs)filled epoxy resin matrix composites,which are prepared by using resin as matrix and HGMs as lightweight filler.Solid buoyancy materials have low density,high strength,low water absorption properties for providing a stable buoyancy for the ocean engineering equipments.The performance of solid buoyancy materials depends not only on the high performance lightweight fillers and resin matrix,but also on the interaction of them.In order to obtain low density and high strength buoyancy materials,decreasing the viscosity of resin system is an helpful method to increase HGMs content and infiltration between HGMs and resin to achieve the high requirements of deep water buoyancy materials.Thus,the development of new type low viscosity epoxy resin system and HGM filled low viscosity epoxy resin composites has great theoretical value and practical significance for ocean engineering.In this paper,epoxy resin E-51 was used as the matrix to systematically study the effects of reactive diluent 678,alicyclic epoxy resin S-184 and the combination of them on the viscosity,density,epoxy value and the curing mechanical properties of epoxy resin.A new low viscosity epoxy resin,which has good liquidity and can be used for the preparation of deep-sea solid buoyancy materials,was prepared,the viscosity of it was 1310 m Pa·S at room temperature(23 °C)and 88 m Pa·S at 60 °C.Using the new low viscosity epoxy resin as matrix,boron amine curing agent 594 and anhydride curing agent Me THPA as curing agent mixture,the cured epoxy resin/594/Me THPA was prepared.The viscosity,suitable period,rheological properties and curing characteristics of this curing system were investigated systematically to reveal the curing reaction mechanism of boron amine-anhydride curing system and optimize the proportion.The results showed that the curing agent system with different Me THPA contents presented a working life with similar viscosity,the viscosity will increase rapidly after this working life.With the increase of Me THPA content,curing reaction activation energy Ea based on the Arrhenius equation was reduced and the curing reaction was promoted.Combined with preparation and curing performance requirements,optimization of Me THPA content was ten.The curing process analysis of the epoxy resin/594/Me THPA curing system showed that the exothermic process of this system existed two exothermic peaks,the lower temperature peak was come from the exothermic of epoxy resin with Me THPA,the higher temperature peak was come from 594 exothermic.In addition,the curing agent 594 and Me THPA in curing system existed both synergistic effect and competitive effect.The mechanical properties of the curing low viscosity epoxy resin system were also studied,the relationship between hardness and curing degree was established and presented a good linear relationship.With a low viscosity epoxy resin,boron amine-anhydride compound curing system and HGMs as the raw material,the moulding technology was adopted to prepare a new type HGMs reinforced low viscosity epoxy resin composite materials.The density,hardness,thermal conductivity,uniaxial compressive strength and hydrostatic strength of the low viscosity epoxy resin composite materials with different HGM content were analyzed.The results showed that density,hardness,thermal conductivity,uniaxial compression and hydrostatic pressure performance were decreased with the increase of HGM content.Compression performance of composite materials was affected by shear damage of HGMs,compression damage of HGMs and axial cracking of composites.The composites presented excellent hydrostatic pressure resistance property,the water absorption of it was only 1.5%,when the quantity content of HGMs in composite was 36% and the hydrostatic pressure reached up to 30 MPa.At the same time,a coefficient K of uniaxial compression strength and hydrostatic strength(water absorption rate was 1%)was built,the coefficient K can be used to predict the using depth of composites according to the results of uniaxial compression strength.Moreover,the 3 D contour plot method was used to built the relationship curve of the composite density,uniaxial compressive strength and hydrostatic strength.Based on the finite element software ABAQUS,uniaxial compression performance and water pressure resistance property of HGMs reinforced low viscosity epoxy resin composites under service condition were simulated,the compression damage behavior and failure mechanism of composites was discussed.Through the finite element simulation,the results found that the spheres will be deformed as the composites was compressed by displacement load.And the spheres will squeeze the resin substrate in the transverse direction,resulting the stress concentration in the center of the contact site between epoxy and HGMs.Under the condition of hydrostatic pressure,the composites were suffered gradually increasing hydrostatic pressure long with the depth increasing.The stress and deformation of the whole structure will present linear increase.HGMs will easy squeeze each other under pressure due to the thinnest epoxy resin in the position of each HGM.Thus,the stress concentration was formed easily at here.When the stress is larger than the structure strength of HGMs,HGMs will be destroyed first.Then,the space will be appeared in every single cell structure,the capacity of it will be decreased and the materials began to absorb water. |
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