| In view of the fact that the resin matrix composite is easy to aging under harsh environment and prone to produce microcracks on the surface under alternating stress,which leads to the deterioration of the materials properties and the shortening of the service life.In this paper,epoxy resin was used as the research object,and aluminum powder was selected as the reinforcement phase,preparing the aluminum powder reinforced epoxy resin composites.Aluminum powder as the second phase reinforced material can improve the mechanical properties of composites,hindering the continued propagation of cracks that have already been formed.Aluminum as a metal material can shield water molecules,enhancing the barrier of composite materials to water molecules and reducing the absorption of water molecules.The phenomenon of volume expansion of aluminum powder in water or air oxidation can be used to fill the microcrack to block the water diffusion channel formed by crack,and to slow down the diffusion of water.Utilizing the high reflection of aluminum to UV,it can reduce the UV absorptivity of composite material.The interface of the aluminum powder/epoxy resin composite was modified to further improved its comprehensive properties.Through the above research,a new type of epoxy resin composite with high strength,high moisture resistance to heat aging and ultraviolet aging was prepared.In this paper,first,aluminum powder with low oxygen content on the surface was prepared by arc spraying under argon protection.This aluminum porwder was added into the epoxy resin to explore the effects of aluminum powder on mechanical properties,hygrothermal aging resistance and UV aging resistance.On the basis that the addition of aluminum powder can improve the mechanical properties and aging properties of composites at the same time,the influence of the morphology of aluminum powder on the composites properties was investigated by changing the size and shape of the particles.Then,surface treatment was carried on the aluminum powder to further improve the properties of the composite.Finally,considering the problem that resin matrix composite is difficult to be evaluated in field,a method for evaluating the aging degree of resin by resistance is put forward.The conclusions of this paper are as follows:(1)The addition of arc sprayed aluminum powder in epoxy resin can effectively improve the absorbability of composite materials to iMPact force.The added aluminum particles can diverge the iMPact force and change the direction of the iMPact force,which makes it difficult to form long cracks under low energy iMPact,thus improving the resistance to crack propagation and mechanical properties of epoxy resin.When the content of aluminum powder is 6 wt.%,the mechanical properties of the composite are the best,the tensile strength and bending strength are 45.1 MPa and 94.6 MPa,respectively,and the wear rate and the average friction coefficient are the lowest,7.52×10-13 m3N-1m-1 and 0.314,respectively.Secondly,the addition of arc spraying aluminum powder in epoxy resin also improves the barrier property of the composite to the water molecules in the environment,reducing the diffusion coefficient,the saturated water absorption and the mechanical property loss rate of the composites after the hygrothermal aging.The composite with 6 wt.%arc spraying aluminum has the best resistance tohygrotherma aging.The loss rate of tensile and bending strength of it is the lowest,9.3%and 9.6%respectively,which are reduced by 49.2%,43.5%respectively coMPared with that of pure epoxy resin.Aluminum powder can also reflect UV light,which can effectively improve the anti-UV aging performance of the composite.The yellowing value and the strength loss rate of the composite decrease with the increase of the addition of aluminum powder.When the addition of arc spraying aluminum powder is 10 wt.%,the loss rate of tensile strength and bending strength of the composite is the lowest,7.9%and 9.2%,respectively,64.1%and 65.4%lower,respectively,than that of pure epoxy resin.(2)The mechanical properties,hygrothermal aging resistance and UV aging resistance of epoxy resin reinforced by spherical aluminum powder or flake aluminum powder with smaller size are better than those of epoxy resin reinforced by arc spraying aluminum powder with larger particle size.The mechanical properties of the composite modified by spherical aluminum powder are better than that of flake aluminum powder.When the addition of spherical aluminum powder is 6 wt.%,the tensile strength and bending strength of the composite reaches to 64.5 MPa and 177.1 MPa,respectively,the wear rate is decreased to 4.71×10-13m3·N-l·m-1,and the average friction coefficient is 0.338.The composite with flake aluminum powder has better hygrothermal aging resistance than that of spherical aluminum powder.When the addition of flake aluminum powder was 3 wt.%,the diffusion coefficient and saturated water absorption of the composites are the least,1.98×10-6m2/s and 3.29%respectively,and the loss rates of tensile strength and bending strength after aging were 6.3%and 9.0%respectively,which were 65.6%and 47.1%lower than those of pure epoxy resin respectively.The wear rate of it was 8.03×10-10m3·N-1·m-1.The UV aging resistance of the composite with flake aluminum powder is also better than that of spherical aluminum powder.After 100 days UV irradiation,the yellowing value of the composite with 4 wt.%flake aluminum powder decreased to +1.13,and the loss rates of tensile strength and flexural strength is 6.0%and 8.6%,respectively,and the wear rate is 1.11 × 10-12m3·N-1·m-1.(3)The composite was damaged by the fatigue iMPact method,the damage area is 0.1%of the sample.After the damage of epoxy resin,the saturation absorption rate and the diffusion coefficient was increased.The water absorption of the epoxy resin is increased by 41.2%than that of the undamaged.The water absorption of the composite material after damage is basically invariable,only shortens the time required to reach saturation water absorption rate.The diffusion coefficient of the composites with spherical aluminum powder was increased by 37.2%coMPared with that undamaged,and only 28.8%by adding flake aluminum powder.The volume expansion of aluminum powder can effectively fill the cracks in the damage composite.Due to the specific surface area of the flake aluminum powder is larger than that of the spherical aluminum powder under the same mass,the flake aluminum powder has a larger volume dilatation rate after oxidation than that of the spherical aluminum powder,making the filling effect of flake aluminum powder is better.The results show that when the particle size of aluminum powder is 1 ?m,the volume expansion rate after oxidation is about 3%.So,the composite material in this paper can only heal the microcracks of nano scale,and the oxidation of aluminum powder does not increase the size of the crack.(4)The interface between aluminum and epoxy resin was modified by silane coupling agent,titanate coupling agent and aluminate coupling agent.The modified effect of silane coupling agent is the best,and the interfacial shear strength after modified reaches 13.94 MPa.The interfacial shear strength after modified by aluminate coupling agent is 10.12 MPa.No modification effect of titanate coupling agent on interface between epoxy resin and aluminum powder.However,the modified interface has a poor resistance to hygrothermal aging.After hygrothermal aging,the interface strength of the composite modified by silane coupling agent,titanate coupling agent and aluminate coupling agent is reduced to 5.77 MPa?5.59MPa and 5.61MPa,respectively.The modified interface has a very poor resistance to UV aging,and the shear strength of the composites modified by silane coupling agent,titanate coupling agent and aluminate coupling agent after UV aging is reduced to 2.81 MPa,2.71 MPa and 2.78 MPa.respectively.(5)The conductivity of carbon fibers is not affected by water molecules.The transverse resistance of the sheet made of carbon fiber increases with the increase of water absorption.The fitted equation of resistivity and water absorption of epoxy resin is y=4.59log10x-6.11,and the fitting coefficient is 0.97.Therefore,the water absorption of epoxy resin can be measured by on-line measuring the resistivity of carbon fiber,which can not only measure the diffusion coefficient of epoxy resin,but also evaluate the degree of wet and thermal aging of epoxy resin. |
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