The Study On The Effect Of Fused Deposition Modeling Parameters On Mechanical Property Of FDM Part

The fused deposition modeling(FDM)is one of the most widely used addivtive manufacturing(AM)systems.The mechanical properties especially the tensile strength and distortion are important for functional parts,and the modeling parameters play a critical role in determining the mechanical property of the part.It is important to study the effect of processing parameters on mechanical properties,which provides theoretical support for the selection of parameters to set the best combination of parameters to print products that meet the requirements.This study explored the mathematical relationships between molding parameters and tensile strength and distortion of FDM products from a theoretical perspective.Centering on this research point,the following researches are mainly carried out in this paper:(1)The research on the relationship between molding parameters and tensile strength of product;(2)The study on the relationship between carbon fiber content and tensile strength of continuous carbon fiber reinforced PLA product;(3)The orthogonal experimental method to explore the interaction between molding parameters;(4)The study on the relationship between parameters and thermal stress and distortion of product.The main achievements of this paper are as follows:The effects of layer thickness,deposition velocity and filling rate on heat transition were mainly studied in the respects of theory and experiment,and the quantitative relationship between bond strength and temperature between adjacent filaments of FDM products was determined.The effect of parameters on formation and failure process of the interface was analyzed.Based on this,the mathematical relationships between the tensile strength and molding parameters of FDM product under the elastic interface and elastic-softening interface states were established.The changing rule of theoretical value of the model with thickness,deposition velocity and filling rate were analyzed,and the validity of this model was verified by experiment.The orthogonal experiment method was used to explore the interaction among parameters.According to the results,the mechanical properties of products could be maximized by setting the best combination of parameters.By analyzing the effects of different parameter combinations on the heat transfer inside the product,the bonding time and bonding strength between adjacent filaments and the tensile strength of the specimen,the interaction laws of parameters were summarized from three perspectives: the internal temperature and bongding strength of the filaments and the tensile strength of the product.This paper studied the effect of carbon fiber content on tensile strength of continuous carbon fiber reinforced polylactic acid(CCFRPLA)fabricated by FDM.The interface failure process between carbon fiber and PLA was studied.The elastic-softening cohesion zone model was used to represent the interface state between carbon fiber and PLA,and the prediction model of the tensile strength of CCFRPLA was established.The relationship between the tensile strength of specimens and the content of carbon fiber was analyzed under the elastic interface state.According to the infiltration of carbon fiber and PLA in the nozzle during the molding process,the effective carbon fiber volume coefficient was introduced into the prediction model,which was influenced by the molding parameters.The distortion is another factor affecting the use of FDM products.The effects of layer thickness and deposition speed on distortion of products were firstly investigated by orthogonal experiment.Secondly,the thermal stress mechanism caused by parameters inside the product was analyzed from the point of interface mechanics.According to cohesion model,the mathematical models between thermal stress of the FDM product and parameters under elastic interface state and elastic-softening interface state were established and the experiment test was proposed to verify the validity of the model.This model reveals the effect mechanism of parameters on the internal thermal stress of FDM products and provides a basis for parameter selection to print products that meet the requirements of distortion.