| At present,thermoplastic composite materials are used for their low density,long-term storage,high toughness,good impact resistance,high production efficiency,easy repair,fast and simple post-molding process,recyclable products,repeatable processing,recycling and other hot spots.It is widely used in the fields of construction,automobile,garden,interior decoration,automobile interior parts and daily life.Natural fiber has attracted much attention as a new environmentally friendly material.Natural plant fiber-reinforced thermoplastic materials not only continue the characteristics of conventional fiber-reinforced thermoplastic composite materials,but also have abundant resources,low density,excellent mechanical properties,low cost,and biomaterials.Advantages such as degradation and short growth cycle] have become an inevitable trend in the scientific development of composite materials.Bamboo fiber is a rigid natural fiber with high strength and low elongation.However,due to its small size and large performance difference,the prepared fiber composite material has the characteristics of unstable quality,large performance variability,and poor heat resistance.,Limiting the application of bamboo fiber in the field of high-performance composite materials.Therefore,in order to prepare continuous bamboo fiber thermoplastic prepreg,this study uses continuous bamboo fiber as the reinforcement and thermoplastic polymer polypropylene(PP)as the matrix.Pressing temperature,hot pressing time,hot pressing pressure,fiber content,etc.),material modification(KH550,MAPP)to control the quality of the prepreg.The performance of the prepreg is evaluated by testing physical and mechanical properties such as tensile properties,resin content,areal density,porosity,water absorption,and thermal expansion coefficient.A single(bundle)fiber interface micromechanical performance test method was established,and the interface performance of three reinforcing fibers and the influence of two different interface modifiers on the interface performance were evaluated by this test method.The main research conclusions of the thesis are as follows:(1)When using the film lamination process to prepare continuous plant fiber thermoplastic prepreg,the pre-tension,hot pressing temperature,hot pressing time,hot pressing pressure,fiber content,KH550 content,and KH550 content will all stretch the prepreg The performance has an impact.The study found that when the preload is 3.92 N,the hot pressing temperature is 191℃,the hot pressing time is 4.24 min,the hot pressing pressure is 8.4MPa,and the fiber content reaches 50%,the KH550 content is 2% and the KH550 content is 2%.,The comprehensive performance of continuous bamboo fiber thermoplastic prepreg is better.Using the Box-Behnken design test in the response surface optimization model,the regression equations of the hot pressing temperature,hot pressing time,and hot pressing pressure with the tensile strength of the prepreg as the response value are obtained.Analysis of variance shows that the model is significant and has a good degree of fit.The order of the influence of each optimization factor on the tensile properties of the prepreg is: hot pressing pressure> hot pressing temperature> hot pressing time.(2)The plant fiber thermoplastic prepreg equipment is constructed by using the melt impregnation process,and the continuous production of the continuous plant fiber thermoplastic prepreg is realized through parameter adjustment.The study found that factors such as rolling temperature,rolling time,and fiber content over the roll will have a certain impact on the quality of prepreg preparation.When the fiber content is 31%,the dipping roller temperature is 110°C,and the film temperature is 145°C.,When the number of rolling is 11 times,when the addition amount of KH550 and MAPP is 2%,the tensile strength reaches the maximum value.(3)By studying the embedded length and aspect ratio of the fiber,the influence of the fiber morphology on the interfacial shear strength is studied,and the feasibility and reliability of the pull-out method for testing the interfacial shear strength are improved.At the same time,the effects of interface modifier KH550 and interface compatibilizer MAPP on IFSS were studied.Studies have concluded that the shape of the fiber can affect the IFSS of a single fiber.As the fiber aspect ratio increases,the IFSS of a single bamboo fiber gradually increases.The addition of KH550 and MAPP can significantly enhance the IFSS of a single bamboo fiber.It can effectively improve the IFSS of a single bamboo fiber,but when the addition amount reaches2%,the increase of the interface modifier has little effect on the increase of the IFSS of a single bamboo fiber.(4)Using the prepregs made by the two processes,through comparative study of their tensile strength and areal density uniformity,it is found that the overall film lamination process is better than the melt dipping process.The specific tensile strength of the bamboo fiber prepreg under the film lamination process is 1.36 times that of the hemp fiber prepreg,which can reach77.57% of the glass fiber prepreg.The tensile strength of the bamboo fiber prepreg under the melt impregnation process is 1.16 times that of the hemp fiber prepreg,which can reach 67.82%of the glass fiber prepreg.(5)The composite material is made by using prepreg and composite felt.Through comparative study of its mechanical strength and water absorption,it is found that the tensile strength of composite material made by prepreg is 109.17-740.02% higher than that of composite felt,and the tensile modulus is increased.98.19-500.60%,flexural strength increased by 47.85-332.65%,flexural modulus increased by 13.01-453.42%,water absorption rate decreased by478.28%-1981.8%,water absorption thickness expansion rate decreased by 369.4-1002.17%.The mechanical properties of the prepreg made by the film lamination process are better than the melt impregnation process,and the water absorption melt impregnation process is better than the film lamination process. |
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