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In this paper, the effects of the adhesive and curing agent contents on the tensile strength, bending strength, gas evolution and gas permeability of three-dimensional printed sand molds are studied. A strength model of the three-dimensional printed sand molds is proposed. The multi-material composite sand mold forming test is carried out. In addition, the mesostructure of the sand mold is studied.

The performances of three-dimensional printed sand mold such as tensile strength, bending strength, gas evolution and gas permeability are studied using the standard test methods. The mesostructure of the sand mold is studied by digital core technology.

A sand mold strength model based on the resin adhesive content, curing agent content and sand mold compactness are obtained. Two types of multi-material composite three-dimensional printed sand molds are proposed. An increase in the curing agent content in the sand mold widens the mesoscopic characteristic size distribution of the sand mold, and large-sized mesostructures appear, resulting in a decrease in the sand mold bearing capacity.

Process parameters that affect the performance of three-dimensional printed sand mold are revealed. The sand mold bearing curve provides a reference for the ultimate design of three-dimensional printed sand mold.

The paper deals with experimental work on the performance and mesostructure of multi-material composite three-dimensional printed sand mold with different contents of adhesive and curing agent. That gives a perspective on future designs of sand mold based on these principles.

The purpose of this paper is to investigate the mechanisms controlling the bond formation among extruded polymer filaments in the fused deposition modeling (FDM) process. The bonding phenomenon is thermally driven and ultimately determines the integrity and mechanical properties of the resultant prototypes.

The bond quality was assessed through measuring and analyzing changes in the mesostructure and the degree of healing achieved at the interfaces between the adjoining polymer filaments. Experimental measurements of the temperature profiles were carried out for specimens produced under different processing conditions, and the effects on mesostructures and mechanical properties were observed. Parallel to the experimental work, predictions of the degree of bonding achieved during the filament deposition process were made based on the thermal analysis of extruded polymer filaments.

Experimental results showed that the fabrication strategy, the envelope temperature and variations in the convection coefficient had strong effects on the cooling temperature profile, as well as on the mesostructure and overall quality of the bond strength between filaments. The sintering phenomenon was found to have a significant effect on bond formation, but only for the very short duration when the filament's temperature was above the critical sintering temperature. Otherwise, creep deformation was found to dominate changes in the mesostructure.

This study provides valuable information about the effect of deposition strategies and processing conditions on the mesostructure and local mechanical properties within FDM prototypes. It also brings a better understanding of phenomena controlling the integrity of FDM products. Such knowledge is essential for manufacturing functional parts and diversifying the range of application of this process. The findings are particularly relevant to work conducted on modeling of the process and for the formulation of materials new to the FDM process.

This study aims to investigate the impact of layer thickness, extrusion temperature, extrusion speed and build plate temperature on the tensile strength, crystallinity achieved during fabrication (herein, in-process crystallinity) and mesostructure of Poly(lactic acid) specimens. Both tensile strength and in-process crystallinity were optimized and verified as the function of processing parameters, and their relationship was thoroughly examined.

The four key technological parameters were systematically varied as factors on three levels, using the statistically designed experiment. Surface response methodology was used to optimize tensile strength and crystallinity for the given ranges of input factors. Optimized factor settings were used in a set of confirmation runs, where the result of optimization was experimentally confirmed. Material characterization was performed using differential scanning calorimetry and X-ray diffraction analysis, while the effect of processing parameters on mesostructure was examined by scanning electron microscopy.

Layer thickness and its quadratic effect are dominant contributors to tensile strength. Significant interaction between layer thickness and extrusion speed implies that these parameters should always be varied simultaneously within designed experiment to obtain adequate process model. As regards, the in-process crystallinity, extrusion speed is part of two significant interactions with plate temperature and layer thickness, respectively. Quality of mesostructure is vital contributor to tensile strength during FDM process, while the in-process crystallinity exhibited no impact, remaining below the 20 per cent margin regardless of process parameter settings.

According to available literature, there have been no previously published investigations which studied the effect of process parameters on tensile strength, mesostructure and in-process crystallinity through systematic variation of four critical processing parameters.

Fused‐deposition (FD) is a robotically controlled “fiber” extrusion process that produces a new class of materials with a variety of controllable mesostructural features related to fiber layout and the presence of voids. Mesostructural features of importance to the stiffness and strength of unidirectionally extruded materials were characterized as a function of the processing variables. Samples were made using the Stratasys FDM1600 Modeler with the P400 acrylonitrile‐butadiene‐styrene plastic. Results showed that the void geometry/density and the extent of bonding between contiguous fibers depended strongly on the fiber gap and extrusion flow rate. Settings for minimum void and maximum fiber‐to‐fiber bonding were determined. Void and bond length densities in the plane transverse to the fiber extrusion direction varied from 4 to 16 per cent and 39 to 73 per cent respectively. The results quantify the important mesostructural features as a function of the FD process variables and are expected to find use with other FD materials.

Analytical/Computational models for the fused deposition (FD) material stiffness and strength as a function of mesostructural parameters are developed. Effective elastic moduli are obtained using the strength of materials approach and an elasticity approach based on the asymptotic theory of homogenization. Theoretical predictions for unidirectional FD‐acrylonitrile butadiene styrene materials are validated with experimentally determined values of moduli and strength. For moduli predictions, the results were found to be satisfactory with difference between experimental and theoretical values of less than 10 percent in most cases.

An experimental study of the mechanical behavior of fused‐deposition (FD) ABS plastic materials is described. Elastic moduli and strength values are determined for the ABS monofilament feedstock and various unidirectional FD‐ABS materials. The results show a reduction of 11 to 37 per cent in modulus and 22 to 57 per cent in strength for FD‐ABS materials relative to the ABS monofilament. These reductions occur due to the presence of voids and a loss of molecular orientation during the FD extrusion process. The results can be used to benchmark computational models for stiffness and strength as a function of the processing parameters for use in computationally optimizing the mechanical performance of FD‐ABS materials in functional applications.

This chapter discusses the impacts of David Maines's scholarship in communication research. The utilities of Maines's scholarship in communication research were first identified in a 1997 session in the annual convention of National Communication Association (NCA) by many leading scholars. This chapter documents the applications of Maines's scholarship in communication research in recent years when communication researchers utilized concepts and arguments constructed by Maines to investigate narratives in relations to Donald Trump's presidential election as well as the COVID-19 pendemic.

This study aims to comprehensively investigate the process-structure-property correlation of acrylonitrile butadiene styrene (ABS) parts manufactured by the overheat material extrusion (Mex) method. This study considers the relationships between the tensile and impact strength with temperature profiles, mesostructures and fracture behaviors of the ABS-printed parts.

The overheat printing condition was generated by using the highest possible printing temperature of the Mex printer used in this study together with cooling fan turned off. Temperature profiles of the polymer rasters were measured to characterize the diffusion time of the deposited rasters. Thermogravimetric analysis, differential scanning calorimetry and melt flow index were performed to study the thermal properties of the ABS feedstock. The mesostructures of the printed ABS samples were characterized by using an optical microscope, while their fracture surface was investigated using a field emission scanning electron microscope. The authors performed the tensile and impact tests following ASTM D3039 and D256-10A, respectively.

The use of the overheat Mex printing could offer better raster diffusion with reduced cooling rate and prolonged diffusion time. Consequently, the overheat printed ABS parts possessed a porosity as low as 1.35% with an increase in the weld length formed between the adjacent rasters of up to 62.5%. More importantly, the overheat printed ABS parts exhibited an increase of up to 70%, 84% and 30% in tensile strain at break, tensile toughness and impact strength, respectively, compared to their normal printed counterparts.

This study provides a facile but effective approach to fabricate highly dense and strong polymeric parts printed by Mex method for end-use applications.

The performance of parts produced by fused filament fabrication is directly related to the printing conditions and to the rheological phenomena inherent to the process, specifically the bonding between adjacent extruded paths/raster. This paper aims to study the influence of a set of printing conditions and parameters, namely, envelope temperature, extrusion temperature, forced cooling and extrusion rate, on the parts performance.

The influence of these parameters is evaluated by printing a set of test specimens that are morphologically characterized and mechanically tested. At the morphological level, the external dimensions and the voids content of the printed specimens are evaluated. The bonding quality between adjacent extruded paths is assessed through the mechanical performance of test specimens, subjected to tensile loads. These specimens are printed with all raster oriented at 90º relative to the tensile axis.

The best performance, resulting from a compromise between surface quality, dimensional accuracy and mechanical performance, is achieved with a heated printing environment and with no use of forced cooling. In addition, for all the conditions tested, the highest dimensional accuracy is achieved in dimensions defined in the printing plane.

This work provides a relevant result as the majority of the current printers comes without enclosure or misses the heating and envelope temperature control systems, which proved to be one of the most influential process parameter.

This paper aims to investigate how the user-controlled parameters of the fused filament fabrication three-dimensional printing process define temperature conditions on the boundary between layers of the part being fabricated and how these conditions influence the structure and strength of the polylactic acid part.

Fracture load in a three-point bending test and calculated related stress were used as a measure. The samples were printed with the long side along the z-axis, thus, in the bend tests, the maximum stress occurred orthogonally to the layers. Temperature distribution on the sample surface during printing was monitored with a thermal imager. Sample mesostructure was analyzed using scanning electron microscopy. The influence of the extrusion temperature, the intensity of part cooling, the printing speed and the time between printing individual layers were considered.

It is shown that the optimization of the process parameters responsible for temperature conditions makes it possible to approximate the strength of the interlayer cohesion to the bulk material strength.

The novelty of the study consists in the generalization of the outcomes. All the parameters varied can be expressed through two factors, namely, the temperature of the previous layer and the extrusion efficiency, determining the ratio of the amount of extruded plastic to the calculated. A regression model was proposed that describes the effect of the two factors on the printed part strength. Along with interlayer bonding strength, these two factors determine the formation of the part mesostructure (the geometry of the boundaries between individual threads).