| 2011th Bachelor |
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Title: Processing Effect on Carbon Fiber/ Epoxy Resin Prepreg with the Lower Curing Temperature by Hot-Melt Writer: Hui Jiang Supervisor: Wei Wu, Xiang Wu Abstract: Melted resin film process of carbon fiber/epoxy prepergs for temperature molding is the way that press the reinforced fiber into prepared to produce the prepergs which are able to cure and mold quickly at 80~100℃. Compared with traditional process, melted resin film process has the advantages of low volatile content and voids, resin content and fiber volume fraction controlled preciously, quality enhanced and environment friendly. Low temperature molding allows products can be cured at low temperature and pressure, which decrease the requirements for molds and reduce the cost. This project use solid and liquid epoxy respectively as matrix, anhydride as curing agent, quaternary ammonium as accelerant, and develop a formula of resin system which can be cured at 80℃, 8 days for storage at ambient temperature, good film forming ability and meets the requirements of melted resin film process. The formula is E-51=33, CYD-011=67, MNA=45~48, quaternary ammonium=1.5~2. Through the research of effect of different curing schedules on casting matrix mechanical strength, the curing schedule of resin system mentioned above is determined as 85℃/2h+120℃/2h+140℃/2h+180℃/2h. Through the research of effect of process parameters on fiber infiltration, the process parameters of prepregs are determined as: 65~70℃ as roller temperature, 5~7r/min as roller velocity, 12~16 times as hot-pressing times .
Title: Improve The Properties of Carbon Fiber Reinforced Epoxy Composite Using Polyamic Acid Writer: Ren Wu Supervisor: Wei Wu, Yong Liu Abstract: Carbon fiber reinforced epoxy composite modified by polyamic acid (PAA) was studied in this paper in order to improve the interlaminar toughness of the CF/epoxy composite.The study was mainly about the preparation and the characterization of epoxy prepreg and composite laminates modified by polyamic acid (PAA). The results indicated that the prepregs prepared in this research had stable physical properties. The laminates had the best performances when the resin content was 40% and there was not pre-reaction between PAA and epoxy. The laminates’ mechanical properties and interlaminar fracture toughness tests showed that mechanical properties and interlaminar fracture toughness increased with the increase of PAA content. When PAA content was 2%, flexural strength, interlaminar shear strength and interlaminar fracture toughness were increased by 45%, 33% and 40%, respectively. SEM tests showed that with the addition of PAA, the interface between fiber and resin matrix became rough indicating the PAA improved the bonding properties between resin matrix and carbon fiber. Thermogravimetric analysis (TGA) showed that when PAA content in the composite was 2.5%, the initial decomposition temperature increased of 10 ℃ and in each temperature zone the weight retention increased with the PAA added. It indicated that the thermal stability of composites increased with the addition of PAA.
Title: Study on Carbon Fiber/Epoxy Resin Composites Toughened by Polyetherimide Writer: Peng Wei Supervisor: Wei Wu, Mingchang Liu Abstract: With theadvances of the engineering plastics application technology, resin matrixand compositematerials inthe currentaerospaceand other fieldshave important applications, but the resin matrixand compositetoughnessis verybad. With hightoughness andhigh heat resistanceofthermoplastictoughened high performanceepoxy resinplasticengineering plastics is today'sindustrialdevelopment Direction. First,this studyexplored that polyetherimidetoughenedE-51/CYD-011epoxy resin, explored the influence ofpolyetherimidecontent on theepoxy resincasting mechanical properties;Secondstudypolyetherimideparticlestoughened carbon fiber/epoxy compositelayer. Obtained the influence of polyetherimide content to carbon fiber / epoxy matrix composite mechanical properties. From the experimentalresultsobtainedwiththe addition ofPEI, the bendingproperties ofcomposite materialsshoweda rising trend, while the compositeinterlaminar shear strengthdecreasefrom the beginning, graduallybecomesincreased,and eventuallyjoined thePEIwith respect tothe compoundis notMaterialsslightlyincreased.TheI-layer composite materialfracture toughness, with the PEIcontent increasesupwardtrend in the20%maximum.
Title: Study on Expoy Resin Modified by Polyamic Acid Writer: Chongyang Yang Supervisor: Wei Wu, Yong Liu Abstract: Epoxy resin possess superior mechanical strength, excellent insulating performance, low curing shrinkage rate and low cost, largely used as paint, adhesive and composites. However, the bad toughness and poor heat-resistant property of epoxy resin limited its application in the area where high strength, high toughness and high heat resistance are requested. Polyamic acid has good compatibility with epoxy resin, high strength and high heat resistance. In this paper, epoxy resin was modified with polyamic acid in order to improve the toughness, heat-resistant property, accelerate the curing rate and lower the curing temperature of epoxy resin/DDS system. The mechanism of curing reaction of polyamic acid and epoxy resin/DDS and the effects of the amount of polyamic acid on the curing behavior, thermal stability and mechanical properties of epoxy resin were studied in particular. The results indicate that carboxyl group, amide group and primary amine presenting in polyamic acid molecular can react with epoxy group to form hydroxyl group which can lower the activation energy of the reaction between epoxy and DDS as well as the curing temperature and improve the curing rate. When the adding amount of polyamic acid is 5wt%, the activation energy reduces to 46.18kJ/mol-1 from 62.80kJ/mol-1, the curing onset temperature drops from 175.9℃ to 138.8℃, the gel time reduces to 46min from 162min. The resin system modified by polyamic acid starts to decompose at about 350℃ and doesn’t present the second decomposition after 520℃,while the epoxy/DDS system starts to decompose in about 280℃ and presents the second decomposition in about 520℃, which indicate the enhancement of thermal stability of epoxy resin. The impact strength is improved by 1.9 times. The tensile strength is decreased slightly. The bending strength is enhanced by 14.7%. These illustrate that polyamic acid reacts with epoxy resin to form interpenetrating polymer networks which can improve the toughness and does not lower the tensile strength excessively. The analysis of SEM indicates that the good compatibility between polyamic acid and epoxy resin and explains the toughness improvement of epoxy resin.
Title: Effect on PET Composites Reinforced by Treated Carbon Fiber Writer: Huang Jiang Supervisor: Wei Wu, Pinpin Shi Abstract: PET exhibits Highly crystallization, smooth surface and good mechanical property in a wide range of temperature. CF is a special fiber with great strength and modulus, good conductivity, low density, corrosion resistance and thermostability. CF has been applied to the modification of engineering plastics. In this experiment, Carbon fiber(CF)/Poly(ethylene terephthalate)(PET) composites were prepared in the twin-screw extruder .The content of carbon fiber is 2,6,10,15 percent respectively. In order to study the effect of carbon fiber surface treatment, carbon fiber was treated with nitric acid and silane coupling agent respectively. In this study, many mechanical properties have been researched, such as tensile strength, flexural strength, flexural modulus and impact strength. Through the comparison between different kinds of specimen, the results showed that CF/PET oxidized with nitric acid and treated with silane coupling agent has the relatively best mechanical property.
Title: Effect on Crystallization and Mechanical Properties of PET Toughened by Carbon Fiber Using Nucleating Agent Writer: Zhi Li Supervisor: Wei Wu, Pinpin Shi Abstract: PET plastic has excellent heat resistance, mechanical properties, resistance to chemicals and electrical insulation resistance, comparing other professional engineering plastics with the lower cost, therefore, there are good prospects for the extensive development of the market. But in the long experience we have seen, due to its molecular chain structure of PET rigid, high glass transition temperature, the actual production process is characterized by too slow crystallization rate, low crystallinity, high mold temperature, and a longer injection period. These largely limits the PET development in the field of engineering plastics. The research added nucleating agent (talc, sodium benzoate) in the PET to study crystallization behavior of PET, by comparing the mechanical properties, thermal properties, extraction, SEM and polarization microscope of PET blends added nucleating agent with pure PET, obtain that the addition of nucleating agents significantly enhanced the crystallization ability and the crystallization rate of PET blends, and the addition of talc blends in PET only play the role of heterogeneous nucleation led to two-phase system, while sodium benzoate and PET’s chemical effect will be made into a homogeneous system. Although the addition of sodium benzoate on the crystallization capacity of PET blend system and enhance the crystallization rate is well, but it will make PET degradation, thus affecting the mechanical properties of blends. Integrating mechanical blends and thermal properties of view, the addition of 1% of Talc is the best. In addition, this study also involved the carbon fiber and thermoplastic resin composition of the fiber reinforced thermoplastic resin molded body, and enhance mechanical properties of PET blends on the basis of adding a nucleating agent, the results prove that the addition of carbon content improve the mechanical properties of PET blends.
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