Nadim S. Hmeidat, Bailey Brown, Xiu Jia, Natasha Vermaak and Brett Compton
Mechanical anisotropy associated with material extrusion additive manufacturing (AM) complicates the design of complex structures. This study aims to focus on investigating the…
Abstract
Purpose
Mechanical anisotropy associated with material extrusion additive manufacturing (AM) complicates the design of complex structures. This study aims to focus on investigating the effects of design choices offered by material extrusion AM – namely, the choice of infill pattern – on the structural performance and optimality of a given optimized topology. Elucidation of these effects provides evidence that using design tools that incorporate anisotropic behavior is necessary for designing truly optimal structures for manufacturing via AM.
Design/methodology/approach
A benchmark topology optimization (TO) problem was solved for compliance minimization of a thick beam in three-point bending and the resulting geometry was printed using fused filament fabrication. The optimized geometry was printed using a variety of infill patterns and the strength, stiffness and failure behavior were analyzed and compared. The bending tests were accompanied by corresponding elastic finite element analyzes (FEA) in ABAQUS. The FEA used the material properties obtained during tensile and shear testing to define orthotropic composite plies and simulate individual printed layers in the physical specimens.
Findings
Experiments showed that stiffness varied by as much as 22% and failure load varied by as much as 426% between structures printed with different infill patterns. The observed failure modes were also highly dependent on infill patterns with failure propagating along with printed interfaces for all infill patterns that were consistent between layers. Elastic FEA using orthotropic composite plies was found to accurately predict the stiffness of printed structures, but a simple maximum stress failure criterion was not sufficient to predict strength. Despite this, FE stress contours proved beneficial in identifying the locations of failure in printed structures.
Originality/value
This study quantifies the effects of infill patterns in printed structures using a classic TO geometry. The results presented to establish a benchmark that can be used to guide the development of emerging manufacturing-oriented TO protocols that incorporate directionally-dependent, process-specific material properties.
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Chad E. Duty, Vlastimil Kunc, Brett Compton, Brian Post, Donald Erdman, Rachel Smith, Randall Lind, Peter Lloyd and Lonnie Love
This paper aims to investigate the deposited structure and mechanical performance of printed materials obtained during initial development of the Big Area Additive Manufacturing…
Abstract
Purpose
This paper aims to investigate the deposited structure and mechanical performance of printed materials obtained during initial development of the Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Laboratory. Issues unique to large-scale polymer deposition are identified and presented to reduce the learning curve for the development of similar systems.
Design/methodology/approach
Although the BAAM’s individual extruded bead is 10-20× larger (∼9 mm) than the typical small-scale systems, the overall characteristics of the deposited material are very similar. This study relates the structure of BAAM materials to the material composition, deposition parameters and resulting mechanical performance.
Findings
Materials investigated during initial trials are suitable for stiffness-limited applications. The strength of printed materials can be significantly reduced by voids and imperfect fusion between layers. Deposited material was found to have voids between adjacent beads and micro-porosity within a given bead. Failure generally occurs at interfaces between adjacent beads and successive layers, indicating imperfect contact area and polymer fusion.
Practical implications
The incorporation of second-phase reinforcement in printed materials can significantly improve stiffness but can result in notable anisotropy that needs to be accounted for in the design of BAAM-printed structures.
Originality/value
This initial evaluation of BAAM-deposited structures and mechanical performance will guide the current research effort for improving interlaminar strength and process control.
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Vijayanand Rajendra Boopathy, Anantharaman Sriraman and Arumaikkannu G.
The present work aims in presenting the energy absorbing capability of different combination stacking of multiple materials, namely, Vero White and Tango Plus, under static and…
Abstract
Purpose
The present work aims in presenting the energy absorbing capability of different combination stacking of multiple materials, namely, Vero White and Tango Plus, under static and dynamic loading conditions.
Design/methodology/approach
Honeycomb structures with various multi-material stackings are fabricated using PolyJet 3D printing technique. From the static and dynamic test results, the structure having the better energy absorbing capability is identified.
Findings
It is found that from the various stacking combinations of multiple materials, the five-layered (5L) sandwich multi-material honeycomb structure has better energy absorbing capability.
Practical implications
This multi-material combination with a honeycomb structure can be used in the application of crash resistance components such as helmet, knee guard, car bumper, etc.
Originality/value
Through experimental work, various multi-material honeycomb structures and impact resistance of single material clearly indicated the inability to absorb impact loads which experiences a maximum force of 5,055.24 N, whereas the 5L sandwich multi-material honeycomb structure experiences a minimum force of 1,948.17 N, which is 38.5 per cent of the force experienced by the single material. Moreover, in the case of compressive resistance, 2L sandwich multi-material honeycomb structure experiences a maximum force of 5,887.5 N, whereas 5L sandwich multi-material honeycomb structure experiences a minimum force of 2,410 N, which is 40.9 per cent of the force experienced by two-layered (2L) sandwich multi-material honeycomb structure. In this study, the multi-material absorbed most of the input energy and experienced minimum force in both compressive and impact loads, thus showing its energy absorbing capability and hence its utility for structures that experience impact and compressive loads. A maximum force is required to deform the single and 2L material in terms of impact and compressive load, respectively, under maximum stiffness conditions.
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Because of the special “State of the States” issue of Library Hi Tech and other circumstances beyond my control, the four quarterly “Comp Lit” compilations for 1996 appear here in…
Abstract
Because of the special “State of the States” issue of Library Hi Tech and other circumstances beyond my control, the four quarterly “Comp Lit” compilations for 1996 appear here in a single and possibly peculiar chunk. A lot changes in a year of personal computing, but on reflection it seemed useful to include the citations and comments as I originally wrote them.
Recognizing the 9/11 attacks as a turning point in the history of American emergency management and response philosophies, this chapter examines the evolution to a standardized…
Abstract
Recognizing the 9/11 attacks as a turning point in the history of American emergency management and response philosophies, this chapter examines the evolution to a standardized National Incident Management System (NIMS). This involved the movement from individual jurisdictional and agency autonomy to adoption of a multilayered system where all efforts are intended to support a response beginning and ending at the local level. This chapter discusses the overarching NIMS doctrine and its incumbent on-scene Incident Command System (ICS) for coordinating on-scene operations. The specific focus is the application to the NIMS and the ICS to law enforcement.
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The steady stream of cases on landlord and tenant matters has continued unabated during 1985 and the early part of this year. Amost every week, reports on decisions of the High…
Abstract
The steady stream of cases on landlord and tenant matters has continued unabated during 1985 and the early part of this year. Amost every week, reports on decisions of the High Court and the Court of Appeal appear in property journals. Decisions often seem to conflict with one another and it is becoming increasingly difficult to keep up to date. Advisers to clients — both landlords and tenants — are constantly seeking fresh nuances of which to take advantage.
Martha E. Williams, Ellen Sutton and Brett Sutton
This is the fourth article on Social Science, Humanities, News and General (SSH) Databases in a continuing series of articles summarizing and commenting on new database products…
Abstract
This is the fourth article on Social Science, Humanities, News and General (SSH) Databases in a continuing series of articles summarizing and commenting on new database products. Two companion articles, one covering science, technology and medicine (STM) (Online & CDROM Review vol. 18 issue 4) and the other covering business and law (BSL) (Online & CDROM Review vol. 18 issue 6) complement this article. The articles are based on the newly appearing database products in the most current edition of the Gale Directory of Databases. The Gale Directory of Databases (GDD) was created in January 1993 by merging Computer‐Readable Databases: A Directory and Data Sourcebook (CRD) with the Directory of Online Databases (DOD) and the Directory of Portable Databases (DPD).
As CD‐ROM becomes more and more a standard reference and technicalsupport tool in all types of libraries, the annual review of thistechnology published in Computers in Libraries…
Abstract
As CD‐ROM becomes more and more a standard reference and technical support tool in all types of libraries, the annual review of this technology published in Computers in Libraries magazine increases in size and scope. This year, author Susan L. Adkins has prepared this exceptionally useful bibliography which she has cross‐referenced with a subject index.
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Martha E. Williams, Ellen Sutton and Brett Sutton
This is the sixth article on social science, humanities, news and general (SSH) databases in a continuing series of articles summarising and commenting on new database products…
Abstract
This is the sixth article on social science, humanities, news and general (SSH) databases in a continuing series of articles summarising and commenting on new database products. There are two companion articles, one covering science, technology and medicine (STM) which appeared in the August 1995 issue (Online & CDROM Review, vol. 19 issue 4) and the other covering business and law (BSL) which will appear in the December issue of this journal (Online & CDROM Review, vol. 19 issue 6). The articles are based on the newly appearing database products in the Gale Directory of Databases. The Gale Directory of Databases (GDD) was created in January 1993 by merging Computer‐Readable Databases: A Directory and Data Sourcebook (CRD) together with the Directory of Online Databases (DOD) and the Directory of Portable Databases (DPD).