Material Extrusion Additive Manufacturing of Poly(Lactic Acid): Influence of infill orientation angle

The effect that the infill orientation angle has on the strain-rate dependence of the yield stress for material extrusion additive manufactured (ME-AM) PolyLactic Acid (PLA) material was investigated. Symmetric angleply stacking sequences were used to produce ME-AM tensile test samples. Measured yield stresses were compensated for the voided structure, typical of ME-AM components. Furthermore, molecular orientation and stretch was macroscopically assessed by a thermal shrinkage procedure. Additionally, hot-press compression molded (CM) samples were manufactured and mechanically characterized in uniaxial tensile and compression in order to determine the material’s isotropic bulk properties. Initial model parameters for the Ree–Eyring modification of the Eyring flow rule were determined using CM data. According to SEM fractography, all samples showed microscopically brittle fracture behavior. Notwithstanding, contrary to CM samples, ME-AM specimens showed macroscopically ductile stress–strain behavior and a transition from a regime with only a primary ��-deformation process, at low strain rates, to a regime with 2 deformation processes (�� + ��), at high strain rates. These effects are an influence of the processing step and are attributed to the molecular orientation and stretch of the polymer chains, provoking anisotropic mechanical properties. As a consequence, a deformation-induced change of the Eyring rate constants is needed to adequately describe the strain-rate dependence of the ME-AM yield stress behavior, leaving the initial activation volumes unchanged. Taking this deformation-dependence of the rate constants into account, yield stresses as a function of infill orientation angle can be appropriately predicted.The authors gratefully thank Carlos D. Jaramillo Vicente for the hot-press compression molded sample experiments and Miguel Casado Ortega for the material extrusion additive manufacturing experiments. Thanks is also acknowledged to Pedro Luis Sánchez Ortega and José María Cámara Nebreda of the DINper research group at the Universidad de Burgos for their initial help with ME-AM processing. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors

Teacher's manual: manufacture of push buttons by 3D printing

Trabajo realizado dentro del proyecto EURODDIP-e, cofinanciado por el programa europeo Erasmus+,European Commissio

Print velocity effects on strain-rate sensitivity of acrylonitrile-butadiene-styrene using material extrusion additive manufacturing

The strain-rate sensitivity of the yield stress for Acrylonitrile-Butadiene-Styrene (ABS) tensile samples processed via material extrusion additive manufacturing (ME-AM) was investigated. Such specimens show molecular orientation and interstitial voids that affect the mechanical properties. Apparent densities were measured to compensate for the interstitial voids. Three different printing speeds were used to generate ME-AM tensile test samples with different molecular orientation. Printing velocities influenced molecular orientation and stretch, as determined from thermal shrinkage measurements. Likewise, infill velocity affected the strain-rate dependence of the yield stress. The ABS material manifests thermorheollogically simple behavior that can correctly be described by an Eyring flow rule. The changing activation volume, as a result of a varying print velocity, scales linearly with the molecular orientation, as captured in an estimated processing-induced pre-strain. Therefore, it is suggested that ME-AM processed ABS shows a deformation-dependent activation volume. This paper can be seen as initial work that can help to improve quantitative predictive numerical tools for ME-AM, taking into account the effects that the processing step has on the mechanical properties

Strain-rate-dependent properties of short carbon fiber-reinforced acrylonitrile-butadiene-styrene using material extrusion additive manufacturing

Purpose – The purpose of the present paper is to quantify and analyze the strain-rate dependence of the yield stress for both unfilled acrylonitrilebutadiene- styrene (ABS) and short carbon fiber-reinforced ABS (CF-ABS) materials, fabricated via material extrusion additive manufacturing (MEAM). Two distinct and opposite infill orientation angles were used to attain anisotropy effects. Design/methodology/approach – Tensile test samples were printed with two different infill orientation angles. Uniaxial tensile tests were performed at five different constant linear strain rates. Apparent densities were measured to compensate for the voided structure. Scanning electron microscope fractography images were analyzed. An Eyring-type flow rule was evaluated for predicting the strain-rate-dependent yield stress. Findings – Anisotropy was detected not only for the yield stresses but also for its strain-rate dependence. The short carbon fiber-filled material exhibited higher anisotropy than neat ABS material using the same ME-AM processing parameters. It seems that fiber and molecular orientation influence the strain-rate dependence. The Eyring-type flow rule can adequately describe the yield kinetics of ME-AM components, showing thermorheologically simple behavior. Originality/value – A polymer’s viscoelastic behavior is paramount to be able to predict a component’s ultimate failure behavior. The results in this manuscript are important initial findings that can help to further develop predictive numerical tools for ME-AM technology. This is especially relevant because of the inherent anisotropy that ME-AM polymer components show. Furthermore, short carbon fiber-filled ABS enhanced anisotropy effects during ME-AM, which have not been measured previously

Manual del docente: fabricación de pulsadores mediante impresión 3D

Trabajo realizado dentro del proyecto EURODDIP-e, cofinanciado por el programa europeo Erasmus+,Comisión Europe

Manual de professores: produçâo e montagem de manípulos por impressâo 3D

Trabajo realizado dentro del proyecto EURODDIP-e, cofinanciado por el programa europeo Erasmus+Comissão Europei

Handleiding voor leerkrachten: vervaardiging en montage van drukknoppen via 3D printen

Trabajo realizado dentro del proyecto EURODDIP-e, cofinanciado por el programa europeo Erasmus+,Europese Commissi

Manuale dell’insegnante: realizzazione e montaggio dei pulsanti per l'utilizzo della stampate 3D

Trabajo realizado dentro del proyecto EURODDIP-e, cofinanciado por el programa europeo Erasmus+,Commissione europe

Density, viscosity, refractive index, and related thermophysical properties of dibutyl ether +2-butanol + cyclohexane ternary systems

Producción CientíficaNew measured data for density, (ρ), dynamic and kinematic viscosities, (μD and μc), and refractive index, (nD), are presented at T = 298.15 K and p = 0.1 MPa for binary and ternary mixtures containing dibutyl ether, 2-butanol, and cyclohexane. As a result, the derived properties are estimated based on the measured data. Excess molar volume, (VE), dynamic viscosity deviation (ΔμD), and deviation in refractive index, (ΔnD), as derived properties, are fitted using the Redlich–Kister equation. In addition, perturbed-chain statistical associating fluid theory equation of state is employed to correlate the measured data of density