Discrete Element Simulation On The Oriented Arrangement Of Carbon Fiber In Nylon Powders With Ultrasonic Vibration Assisting

Selective laser sintering(SLS)of carbon fiber reinforced nylon composite powders is a new technology in additive manufacturing.To achieve a layering and oriented arrangement of carbon fibers in the powder paving process,as well as the sintered part has a similar "woven"microstructure,then the better mechanical properties are obtained,which is the major breakthrough point of this technology.A method of ultrasonic vibration assisting oriented arrangement of carbon fiber in nylon powders was presented in this paper.Discrete element method was used to simulate the process,and a preliminary test has been carried out,the influence rule of vibration parameters of ultrasonic vibration and the aspect ratio of carbon fiber on the carbon fiber ordered arrangement was also discussed.According to the geometric characteristics and micro-mechanical properties of nylon powder and carbon fiber,a discrete element model of the ultrasonic vibration system of carbon fiber/nylon powder material was established.The ultrasonic vibration parameters were set by a simple harmonic vibration equation to simulate the movement process of the carbon fiber/nylon composite powder layer under the different vibration conditions,the fiber orientation frequency and orientation probability entropy were taken as criteria to evaluate the arrangement status and ordering of carbon fiber,the vibration amplitude,frequency and vibration time,as well as the aspect ratio of carbon fiber on the influence rule of arrangement status and ordering were analyzed.The effect of the amplitude,frequency,and vibration time of ultrasonic vibration on the orientation of carbon fibers in nylon powders was preliminarily verified on a self-built experimental bench.The numerical simulation of various vibration processes was carried out by means of orthogonal test.The generating mechanism of carbon fiber's oriented arrangement was studied,and the influence mechanism of each vibration parameter was also discussed.The results shown that the amplitude has a significant influence on the ordering of carbon fibers,the frequency and the vibration time both are secondary influence.And within the parameters of the orthogonal scheme,the optimum conditions of ultrasonic vibration frequency,amplitude and vibration time were obtained,namely the frequency is 20kHz,the amplitude is 1?m,and the vibration time is Is.The study in this paper lays the foundation for further research on the layering and oriented arrangement technology of carbon fibers.