Study Of Combustion Behavior Of 3D Printed Porous Structured Polylactic Acid

The application of polylactic acid(PLA)in radiators has a very promising potential,but its flammability increases the risk of the application.In addition,the fire performance of radiators may be related to their pore structure,yet it is not clear how the pore structure affects the scientific aspects of the fire safety of PLA-prepared radiators.Therefore,this article verifies the effect of pore structure variation of PLA on fire safety and proposes a novel system combining 3D printing,cone calorimetry(CC),fire numerical simulation and theoretical validation for evaluating the fire safety of pore structure(pore shape,size and interval).The results of the study all show that changing the structural design of the holes significantly improves their fire safety.Based on this,the main results of this study are as follows:(1)The conclusions concluded from the different hole structure samples in laboratory tests and fire simulations are consistent:The combustion behavior of PLA materials is closely related to different pore structure characteristics,and the fire safety of PLA can be improved by changing the physical structure design of the material.The hexagonal pore shape has the highest fire safety,followed by triangle,parallelogram,honeycomb and square;the pore size and interval groups also have a similar regularity,and it is found that adjusting the pore size and interval can improve its fire performance,and both show that the smaller size and interval,the better the fire performance.Among them,Fhexagonal,S2mm and I2mm all show the lowest fire hazard,and their peak heat release rate(HRR)are only 65%,40%and 51%of the worst fire performance samples,respectively.(2)New formulas for the characteristic length(Lc)and Rayleigh(Ra)which areLc=4εr0Ac/rPln(|cosθ|+C)and Ra=64βρgc·Tr03ε5Ac3/U0λ02r3P3[ln(|cosθ|+C)]3,respectively,are defined to obtain new theoretical connections arising between them and HRR:an increase in the values of Lc and Ra means that the HRR values of the specimens will increase significantly;in addition,by setting the characteristic shape factor reflecting the characteristic factors of the pores,expressions for characteristic shape factor(Sc)and HRR are derived for different pore structure conditions:when s and i are certain,y=e1.645+0.109Sc+0.021Sc2,whenθ,r and i are sure,y=20.309-18.536×0.790Sc,and when θ,r and s are certain,y=32.671eSc/0.108+7.128.(3)The relationship between HRR and combustion and heat transfer behavior of PLA pore structure is elaborated.Combined with the correlation analysis of multiple effects of "orifice closure","vortex heat dissipation","narrow-angle variable speed"and structural advantages,it shows the corresponding relationship between convective heat dissipation and HRR and theoretically analyzes that adjusting the pore structure can improve its fire safety.By testing the fire safety of hole shape,size and interval,the influence of hole structure on the fire performance of materials is studied,aiming to provide certain basic theoretical guidance for the application of hole structure materials in fire safety.