Preparation And Selective Laser Sintering Of Carbon Fibre/polyamide 12 Composite Powders

Selective Laser Sintering is one of the Solid Freeform Fabrication technologies, which sinters powder materials into 3D solid components. One of the most important branches of SLS application is to directly fabricate plastic structural components by polymer and polymer-matrix composite powders, and it has a promising market. However, to meet further requirements of high dimensional accuracy, eminent mechanical properties and fine thermal stability, research and development of novel polymer and polymer-matrix composite powders for SLS processing are of great importance. Compared with Europe and America, the R&D of SLS materials in China is relatively inferior. With less variety and poor properties, the SLS powder materials become the bottleneck which impedes the development of SLS in china. Therefore, aiming at developing carbon fibre/polyamide 12 composite powder for SLS of high-performance plastic structural components, the preparation of composite powders, sintering process, as well as mechanical properties of sintered components were studied in this paper. The main content and result of this research are as below:3 kinds of CF/PA composite powders were prepared, with fibre content of 30%, 40%, 50%, respectively. Particle size and partical size distribution of the composite powder were measured, micro-mophology was observed via Scanning Electron Microscope, and thermal properties of the composite powder were analyzed. The results showed that: the CF/PA composite powder has a wide particle size distribution and have an average particle size around 50 and 60μm; the melting point of the composite powder declines a little with the increase of fibre content; the crystal temperature increase by 7℃and it seems to remain constant with different fibre contents; the themal stability of the composite powder is greatly enhanced, and the peak temperature of thermal degradation speed increases by about 30℃.The mechanism of selective laser sintering CF/PA composite powder was sdudied, influence of SLS processing parameters on CF/PA sintered components was analyzed, and an appropriate set of processing parameters were determined for the CF/PA composite powders by analysis and experiments. The preheat temperatures for 30%, 40%, 50% CF/PA composite powder were 170℃, 168℃, 165℃, respectively. Laser power, scanning speed, scanning spacing, and layer thickness were set to be 22W, 2000mm/s, 0.1mm, 0.1mm, respectively. In-out helical scanning method was adopted and believed to diminish the curling tendency during the sintering process.The influence of carbon fibre content on mechanical properties of sintered components was analyzed. The results showed that: carbon fibre could greatly enhanced the flexural strength and flexural modulus of sintered components; the flexural strengths of 3 CF/PA sintered components are enhanced by 44.5%, 83.3%, 114%, respectively; and the flexural modulus are enhanced by 93.4%, 129.4%, 243.4%, respectively; the impact strength declined, compared with sintered nylon components. The impact strength of CF/PA sintered components is 64.2% of sintered nylon parts while the fibre content is 50 wt. %.From the fracture morphology of the sintered components, the distribution of carbon fibre in the matrix was observed, and the fracture mechanism was analyzed, which further explained the influence of carbon fibre on mechanical properties of sintered composite components.