Laser-based additively manufactured polymers: a review on processes and mechanical models
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Laser-based additively manufactured polymers: a review on processes and mechanical models Roberto Brighenti1,* Michele Terzano1 1 2
, Mattia Pancrazio Cosma1
, Liviu Marsavina2
, Andrea Spagnoli1
, and
Department of Engineering and Architecture, University of Parma, Parco Area delle Scienze 181/A, 43124 Parma, Italy Department of Mechanics and Strength of Materials, University Politehnica Timisoara, Blvd. M. Viteazu, Nr. 1, 300222 Timisoara, Romania
Received: 22 May 2020
ABSTRACT
Accepted: 1 September 2020
Additive manufacturing (AM) is a broad definition of various techniques to produce layer-by-layer objects made of different materials. In this paper, a comprehensive review of laser-based technologies for polymers, including powder bed fusion processes [e.g. selective laser sintering (SLS)] and vat photopolymerisation [e.g. stereolithography (SLA)], is presented, where both the techniques employ a laser source to either melt or cure a raw polymeric material. The aim of the review is twofold: (1) to present the principal theoretical models adopted in the literature to simulate the complex physical phenomena involved in the transformation of the raw material into AM objects and (2) to discuss the influence of process parameters on the physical final properties of the printed objects and in turn on their mechanical performance. The models being presented simulate: the thermal problem along with the thermally activated bonding through sintering of the polymeric powder in SLS; the binding induced by the curing mechanisms of light-induced polymerisation of the liquid material in SLA. Key physical variables in AM objects, such as porosity and degree of cure in SLS and SLA respectively, are discussed in relation to the manufacturing process parameters, as well as to the mechanical resistance and deformability of the objects themselves.
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The Author(s) 2020
Handling Editor: Maude Jimenez.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05254-6
J Mater Sci
GRAPHIC ABSTRACT MODELLING
POLYMERIC POWDER (SLS)
TRANSFORMATION
RAW MATERIAL
LIQUID RESIN (SLA)
PROCESS PARAMETERS optical model thermal model sintering model kinetic model
SINTERING (SLS)
CURING (SLA)
FINAL PART PRINTED COMPONENT
MECHANICAL PROPERTIES
List of symbols
Common parameters cp Specific heat (J K-1 kg-1) d Layer thickness (m) E Young’s modulus (Pa) F Deformation gradient (–) h Part thickness (m) I Laser intensity (W m-2) I0 Maximum laser intensity (W m-2) kB Boltzmann’s constant (J K-1) qg Internal heat generation (W m-3) R Universal gas constant (m3 Pa K-1 mol-1) t Time (s) T Temperature (K) Tg Glass transition temperature (K) DE Activation energy (J mol-1) e Engineering strain (–) g Viscosity (Pa s) j Bulk modulus (Pa) k Thermal conductivity (W m-1 K-1) l Shear modulus (Pa) q Mass density (Kg m-3) r Cauchy stress (Pa)
rB ry s
mechanical model
Stefan–Boltzmann’s constant (W m-2 K-4) Yield stress (Pa) Viscous relaxation time (s)
Selective laser sintering parameters a Powder partic
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