Study On Preparation And Properties Of Syntactic Foams For Deep Sea Application

In this thesis,syntactic foams were fabricated by casting method with epoxy resin(E51)as the matrix,hollow glass microspheres(HGMs)as lightweight filler.According to the problem that gas defects in syntactic foams and the poor interfacial strength between HGMs and epoxy resin,the ultrasonic treatment technology was proposed.In order to enhance the interfacial strength between HGMs and epoxy resin,the effect of coupling agent on the properties of syntactic foams were studied.The effect of different proportions of HGMs on the properties of syntactic foams were studied.Using neat carbon nanotube,carboxyl-functionalized and amino-functionalized carbon nanotube as reinforcement to fabricate carbon nanotube/HGMs/epoxy syntactic foams,and the effect of functionalized carbon nanotubes on the properties of syntactic foams were studied.The results of the study are showed as follow:1.With increasing the content of HGMs,the compressive strength of syntactic foam increases first and then decreases after ultrasonic treatment on HGMs/epoxy resin mixture.When the content of HGMs is 60vol%,the compressive strength and specific compressive strength are 39 MPa and 65MPa·cm3·g-1 respectively,which are increased by 15.4% and 8.3% than syntactic foams without ultrasonic treatment.Ultrasonic vibration and linear alternating flow effect will generate high frequency vibration of HGMs in the matrix.The gas which is attached to the surface of the HGMs enters into the matrix then escapes from mixture.So the gas defects in the sample are reduced,that will lead to the stress concentration point reduces,and the compressive strength is increased.2.With the addition of coupling agent,a transition layer with thickness of about 1.2~1.5?m was formed between HGMs and epoxy resin matrix which enhance the interfacial strength between HGMs and epoxy resin matrix.When the cracks spread to HGMs,a part of HGMs are submitted to shear failure;another part of HGMs change the propagation direction of cracks,which lead to the energy consumption,thereby the compressive properties of samples are enhanced.3.Syntactic foams were fabricated by different mixing ratio of K25 and S38 HS,K25 and S60 HS HGMs.It is found that: due to the low density and low compressive strength of K25,with the increase of the content of HGMs,the compressive strength and density of specimen gradually decrease.Because of the small size and high compressive strength of S60 HS,it can be well dispersed in the matrix and can be used as the reinforcing phase.So the compressive properties of syntactic foams which are fabricated by K25 and S60 HS are prior to that of syntactic foam which are fabricated by K25 and S38 HS.4.Due to the better binding ability and better dispersibility of amino-functionalized carbon nanotube,the reinforcement effect of amino carbon nanotube is better than carboxyl carbon nanotube.When the content of amino carbon nanotube is 0.3wt%,the compressive properties of syntactic foam are the best,the compressive strength and the specific compressive strength are 50 MPa and 92MPa·cm3·g-1 respectively,which are increased by 16% and 25% than syntactic foams without carbon nanotubes.Carbon nanotubes are dispersed in epoxy resin matrix by ultrasonic,which cause the viscosity of carbon nanotubes/HGMs/epoxy resin mixture sharply to increase,and hinder the escape of gas,so the density of syntactic foam decreases sharply.