Preparation And Characterization Of Nylon 12/carbon Fibers/epoxy Composites Based On Selective Laser Sintering

Due to the excellent strength,modulus and thermal resistance,chemical corrosion resistance and light weight,carbon fiber reinforced thermosetting epoxy resin composites have been widely applied in aerospace,transportation,construction,electronics and other fields.Carbon fibers?CF?can greatly improve the strength and other mechanical properties of epoxy resin.However,the low fracture toughness of epoxy resin after curing and difficulties for traditional manufacturing processes in fabricating complex parts make it unable to meet the requirements of high toughness and high geometrical complexity.In this work,the polyamide 12?PA12?coated carbon fiber composite powders were prepared by the dissolution-precipitation method.Then,selective laser sintering?SLS?additive manufacturing technology was employed to fabricate green parts.After low viscosity epoxy resin infiltration and curing processing,the fully dense nylon 12/carbon fiber/epoxy resin composite parts were fabricated.The main research contents and findings of this paper are as follows:During the preparation of nylon 12/carbon fiber composite powder,the influence of cooling process on PA12/CF composite powder surface topography and bulk density was studied and an optimized cooling procedure were utilized to prepare the PA12/CF composite powder suitable for SLS.In the SLS process,the relationships between laser power,layer thickness and porosity,dimensional accuracy were investigated,and the results show that the laser power of 8W and layer thickness of 0.15mm were the optimum processing parameters.Compared to pure epoxy resin,PA12/CF/EP composite specimens with the PA12contents of 20%,30%,40%,50%in green parts show 92.8%,125.0%,106.0%,86.2%higher of tensile strength respectively,and elastic modulus are enhanced by 123.2%,85.9%,43.8%,36.9%respectively.Furthermore,the mechanical properties on X direction always precede those on Y direction.The Micro-CT measurements indicated the fiber orientation factor1)=0.12.A modified Kelly-Tyson model was developed to predicate the tensile strength,while Halpin-Tsai model was utilized to calculate the tensile modulus and the theoretical values are very close to the experimental values.in addition,the stress intensity factorof 20,30,40,50%PA12/CF/EP are 1.81,1.87,1.99,2.05 MPa?8)^1?2 respectively,indicating the increase in fracture toughness with increasing PA12content in ternary composites.In this work,the additive manufacturing technology was used to prepare short carbon fiber reinforced epoxy composites.Not only the mechanical properties as well as fracture performance were improved,but also the composite parts with complex geometries could be fabricated,and thus the application scope of epoxy resin can be expanded.