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This study aims to investigate the material extrusion additive manufacturing (MEAM) deposition parameters for creating viable 3-D printed polyvinylidene fluoride (PVDF) structures with a balanced mix of mechanical and electrical properties.

Different combinations of deposition conditions are tested, and the influence of these parameters on the final dimensional accuracy, semi-crystalline phase microstructure and effective mechanical strength of MEAM homopolymer PVDF printed parts is experimentally assessed. Considering printed part integrity, appearance, print time and dimensional accuracy, MEAM parameters for PVDF are suggested.

A range of viable printing parameters for MEAM fabricated PVDF Kynar 740 objects of different heights and in-plane length dimensions was determined. For PVDF structures printed under the suggested conditions, the mechanical response and the microstructure development related to Piezoelectric response are reported.

This research first reports on a range of parameters that have been confirmed to facilitate effective MEAM printing of 3-D PVDF objects, presents effects of the individual parameters and gives the mechanical and microstructure properties of PVDF structures fabricated under the suggested deposition conditions.

The purpose of this paper is to study the shape memory properties of SMP samples produced through a MEAM process. Fused deposition modeling or, as it will be referred to in this paper, material extrusion additive manufacturing (MEAM) is a technique in which polymeric materials are extruded though a nozzle creating parts via accumulation and joining of different layers. These layers are fused together to build three-dimensional objects. Shape memory polymers (SMP) are stimulus responsive materials, which have the ability to recover their pre-programmed form after being exposed to a large strain. To induce its shape memory recovery movement, an external stimulus such as heat needs to be applied.

This project investigates and characterizes the influence of print orientation and infill percentage on shape recovery properties. The analyzed shape recovery properties are shape recovery force, shape recovery speed and time elapsed before activation. To determine whether the analyzed factors produce a significant variation on shape recovery properties, t-tests were performed with a 95% confidence factor between each analyzed level.

Results proved that print angle and infill percentage do have a significant impact on recovery properties of the manufactured specimens.

The manufacturing of SMP objects through a MEAM process has a vast potential for different applications; however, the shape recovery properties of these objects need to be analyzed before any practical use can be developed. These have not been studied as a function of print parameters, which is the focus of this study.

The weakest point in additively manufactured polymer parts produced by material extrusion additive manufacturing (MEAM) is the interface between adjacent layers and deposition toolpaths or “roads”. This study aims to predict the mechanical strength of parts by utilizing a novel analytical approach. Strength predictions are made using the temperature history of these interfaces, polymer rheological data, and polymer weld theory.

The approach is validated using experimental data for two common 3D-printed polymers: polycarbonate (PC) and acrylonitrile butadiene styrene (ABS). Interface temperature history data are collected in situ using infrared imaging. Rheological data of the polycarbonate and acrylonitrile butadiene styrene used to fabricate the fused filament fabrication parts in this study have been determined experimentally.

The strength of the interfaces has been predicted, to within 10% of experimental strength, using polymer weld theory from the literature adapted to the specific properties of the polycarbonate and acrylonitrile butadiene styrene feedstock used in this study.

This paper introduces a novel approach for predicting the strength of parts produced by MEAM based on the strength of interfaces using polymer weld theory, polymer rheology, temperature history of the interface and the forces applied to the interface. Unlike methods that require experimental strength data as a prediction input, the proposed approach is material and build orientation agnostic once fundamental parameters related to material composition have been determined.

This paper aims to present a survey concerning the accuracy of thermoplastic polymeric parts fabricated by additive manufacturing (AM). Based on the scientific literature, the aim is to provide an updated map of trends and gaps in this relevant research field. Several technologies and investigation methods are examined, thus giving an overview and analysis of the growing body of research.

Permutations of keywords, which concern materials, technologies and the accuracy of thermoplastic polymeric parts fabricated by AM, are used for a systematic search in peer-review databases. The selected articles are screened and ranked to identify those that are more relevant. A bibliometric analysis is performed based on investigated materials and applied technologies of published papers. Finally, each paper is categorised and discussed by considering the implemented research methods.

The interest in the accuracy of additively manufactured thermoplastics is increasing. The principal sources of inaccuracies are those shrinkages occurring during part solidification. The analysis of the research methods shows a predominance of empirical approaches. Due to the experimental context, those achievements have consequently limited applicability. Analytical and numerical models, which generally require huge computational costs when applied to complex products, are also numerous and are investigated in detail. Several articles deal with artificial intelligence tools and are gaining more and more attention.

The cross-technology survey on the accuracy issue highlights the common critical aspects of thermoplastics transformed by AM. An updated map of the recent research literature is achieved. The analysis shows the advantages and limitations of different research methods in this field, providing an overview of research trends and gaps.

During 2011, the Making Every Adult Matter (MEAM) coalition supported three pilots to better coordinate existing local services for people facing multiple needs and exclusions. These individuals experience a combination of problems such as homelessness, substance misuse, mental health problems and offending. Many face difficulties consistent with dual diagnosis in its broadest sense. The purpose of this paper is to summarise the evaluation of the pilots, undertaken by FTI Consulting/Compass Lexecon in partnership with Pro Bono Economics.

The evaluation examined the three pilots, which took place in Cambridgeshire, Derby and Somerset in England. The study looked at two main effects as individuals engaged with better coordinated services: changes in wellbeing and, changes in the use and cost of wider local services. Primary wellbeing data were collected from clients and primary service use data were collected directly from relevant local agencies (police, health, housing etc). The study followed 39 individuals across the pilot sites. The average period between initial and final measurements was nine months.Findings – The findings show significant improvements in wellbeing for nearly all clients across three quantitative measures. The evaluation also recorded changes in the use and cost of local services. Some costs decreased in the first year of the pilot, for example, criminal justice costs in the Cambridgeshire and Somerset pilot areas. Other costs increased in the first year as people accessed the help they needed. In Cambridgeshire, the reduction in crime costs (£100,000 or 31 percent) was large enough to lead to an overall cost reduction. The total cost of service use in the first year increased in the other two areas.

Collecting primary data on clients’ actual service use directly from local agencies provides a strong methodological base. The evaluation will continue for a further year to examine the longitudinal impact of the pilots. The evaluation findings are of relevance to service providers, commissioners and policy makers interested in improving services for people facing multiple needs and exclusions.

Regardless of the materials used, additive manufacturing (AM) is one of the most popular emerging fabrication processes used for creating complex and intricate structural components. This study aims to investigate the effects of process parameters – namely, nozzle diameter, layer thickness and infill density on microstructure as well as the mechanical properties of 17–4 PH stainless steel specimens fabricated via material extrusion AM.

The experimental approach investigates the effects of printing parameters, including nozzle diameter, layer thickness and infill density, on surface roughness, physical and mechanical properties of the printed specimens. The tests were triplicated to ensure reproducibility of the experimental results.

The highest ultimate tensile strength, 795.26 MPa, was obtained on specimen that was fabricated with a 0.4 mm nozzle diameter, 0.14 mm layer thickness and 30% infill density. Furthermore, a 0.4 mm nozzle diameter also provided slightly better ductility. This came at the expense of surface finishing, as a 0.25 mm nozzle diameter exhibited better surface finishing over a 0.4 mm nozzle diameter. Infill density was shown to slightly influence the tensile properties, whereas layer thickness showed a significant effect on surface roughness. By contrast, hardness and ductility were independent of nozzle diameter, layer thickness and infill density.

This paper presents a comprehensive analysis relating to various input printing parameters on microstructural, physical and mechanical properties of additively manufactured 17–4 PH stainless steel to improve the printability and processability via AM.

Extrusion width, the width of printed filaments, affects multiple critical aspects in mechanical properties in material extrusion additive manufacturing: filament geometry, interlayer load-bearing bonded area and fibre orientation for fibre-reinforced composites. However, this study aims to understand the effects of extrusion width on 3D printed composites, which has never been studied systematically.

Four polymers with and without short-fibre reinforcement were 3D printed into single-filament-wide specimens. Tensile properties, mechanical anisotropy and fracture mechanisms were evaluated along the direction of extruded filaments (F) and normal to the interlayer bond (Z). Extrusion width, nozzle temperature and layer height were studied separately via single-variable control. The extrusion width was controlled by adjusting polymer flow in the manufacturing procedure (gcode), where optimisation can be achieved with software/structure design as opposed to hardware.

Increasing extrusion width caused a transition from brittle to ductile fracture, and greatly reduced directional anisotropy for strength and ductility. For all short fibre composites, increasing width led to an increase in strain-at-break and decreased strength and stiffness in the F direction. In the Z direction, increasing width led to increased strength and strain-at-break, and stiffness decreased for less ductile materials but increased for more ductile materials.

The transformable fracture reveals the important role of extrusion width in processing-structure-property correlation. This study reveals a new direction for future research and industrial practice in controlling anisotropy in additive manufacturing. Increasing extrusion width may be the simplest way to reduce anisotropy while improving printing time and quality in additive manufacturing.

This study/paper aims to develop fundamental understanding of mechanical properties for multiple fibre-reinforced materials by using a single-filament-wide tensile-testing approach.

In this study, recently validated single-filament-wide tensile-testing specimens were used for four polymers with and without short-fibre reinforcement. Critically, this specimen construct facilitates filament orientation control, for representative longitudinal and transverse composite directions, and enables measurement of interlayer bonded area, which is impossible with “slicing” software but essential in effective property measurement. Tensile properties were studied along the direction of extruded filaments (F) and normal to the interlayer bond (Z) both experimentally and theoretically via the Kelly–Tyson model, bridging model and Halpin–Tsai model.

Even though the four matrix-material properties varied hugely (1,440% difference in ductility), consistent material-independent trends were identified when adding fibres: ductility reduced in both F- and Z-directions; stiffness and strength increased in F but decreased or remained similar in Z; Z:F strength anisotropy and stiffness anisotropy ratios increased. Z:F strain-at-break anisotropy ratio decreased; stiffness and strain-at-break anisotropy were most affected by changes to F properties, whereas strength anisotropy was most affected by changes to Z properties.

To the best of the authors’ knowledge, this is the first study to assess interlayer bond strength of composite materials based on measured interlayer bond areas, and consistent fibre-induced properties and anisotropy were found. The results demonstrate the critical influence of mesostructure and microstructure for three-dimensional printed composites. The authors encourage future studies to use specimens with a similar level of control to eliminate structural defects (inter-filament voids and non-uniform filament orientation).