585 research outputs found
Polymers and Their Application in 3D Printing
Dear Colleagues, Fused filament fabrication, also known as 3D printing, is extensively used to produce prototypes for applications in, e.g., the aerospace, medical, and automotive industries. In this process, a thermoplastic polymer is fed into a liquefier that extrudes a filament while moving in successive X–Y planes along the Z direction to fabricate a 3D part in a layer-by-layer process. Due to the progressive advances of this process in industry, the application of polymeric (or even composite) materials have received much attention. Researchers and industries now engage in 3D printing by implementing numerous polymeric materials in their domain. In this Special Issue, we will present a collection of recent and novel works regarding the application of polymers in 3D printing
A new mixed model based on the enhanced-Refined Zigzag Theory for the analysis of thick multilayered composite plates
The Refined Zigzag Theory (RZT) has been widely used in the numerical analysis of multilayered
and sandwich plates in the last decay. It has been demonstrated its high accuracy in predicting global quantities, such as maximum displacement, frequencies and buckling loads, and local quantities such
as through-the-thickness distribution of displacements and in-plane stresses [1,2]. Moreover, the C0
continuity conditions make this theory appealing to finite element formulations [3]. The standard RZT,
due to the derivation of the zigzag functions, cannot be used to investigate the structural behaviour
of angle-ply laminated plates. This drawback has been recently solved by introducing a new set of
generalized zigzag functions that allow the coupling effect between the local contribution of the zigzag
displacements [4]. The newly developed theory has been named enhanced Refined Zigzag Theory (en-
RZT) and has been demonstrated to be very accurate in the prediction of displacements, frequencies,
buckling loads and stresses. The predictive capabilities of standard RZT for transverse shear stress
distributions can be improved using the Reissner’s Mixed Variational Theorem (RMVT). In the mixed
RZT, named RZT(m) [5], the assumed transverse shear stresses are derived from the integration of local
three-dimensional equilibrium equations. Following the variational statement described by Auricchio
and Sacco [6], the purpose of this work is to implement a mixed variational formulation for the en-RZT,
in order to improve the accuracy of the predicted transverse stress distributions. The assumed kinematic
field is cubic for the in-plane displacements and parabolic for the transverse one. Using an appropriate
procedure enforcing the transverse shear stresses null on both the top and bottom surface, a new set
of enhanced piecewise cubic zigzag functions are obtained. The transverse normal stress is assumed as
a smeared cubic function along the laminate thickness. The assumed transverse shear stresses profile
is derived from the integration of local three-dimensional equilibrium equations. The variational functional
is the sum of three contributions: (1) one related to the membrane-bending deformation with a
full displacement formulation, (2) the Hellinger-Reissner functional for the transverse normal and shear
terms and (3) a penalty functional adopted to enforce the compatibility between the strains coming
from the displacement field and new “strain” independent variables. The entire formulation is developed
and the governing equations are derived for cases with existing analytical solutions. Finally, to assess
the proposed model’s predictive capabilities, results are compared with an exact three-dimensional solution,
when available, or high-fidelity finite elements 3D models. References: [1] Tessler A, Di Sciuva
M, Gherlone M. Refined Zigzag Theory for Laminated Composite and Sandwich Plates. NASA/TP-
2009-215561 2009:1–53. [2] Iurlaro L, Gherlone M, Di Sciuva M, Tessler A. Assessment of the Refined
Zigzag Theory for bending, vibration, and buckling of sandwich plates: a comparative study of different
theories. Composite Structures 2013;106:777–92. https://doi.org/10.1016/j.compstruct.2013.07.019.
[3] Di Sciuva M, Gherlone M, Iurlaro L, Tessler A. A class of higher-order C0 composite and sandwich
beam elements based on the Refined Zigzag Theory. Composite Structures 2015;132:784–803.
https://doi.org/10.1016/j.compstruct.2015.06.071. [4] Sorrenti M, Di Sciuva M. An enhancement
of the warping shear functions of Refined Zigzag Theory. Journal of Applied Mechanics 2021;88:7.
https://doi.org/10.1115/1.4050908. [5] Iurlaro L, Gherlone M, Di Sciuva M, Tessler A. A Multi-scale
Refined Zigzag Theory for Multilayered Composite and Sandwich Plates with Improved Transverse Shear
Stresses, Ibiza, Spain: 2013. [6] Auricchio F, Sacco E. Refined First-Order Shear Deformation Theory
Models for Composite Laminates. J Appl Mech 2003;70:381–90. https://doi.org/10.1115/1.1572901
Ensemble of four metaheuristic using a weighted sum technique for aircraft wing design
Recently, metaheuristics (MHs) have become increasingly popular in real-world engineering applications such as in the design of airframes structures and aeroelastic designs owing to its simple, flexible, and efficient nature. In this study, a novel hybrid algorithm is termed as Ensemble of Genetic algorithm, Grey wolf optimizer, Water cycle algorithm and Population base increment learningusing Weighted sum (E-GGWP-W), based on the successive archive methodology of the weighted population has been proposed to solve the aircraft composite wing design problem. Four distinguished algorithms viz. a Genetic algorithm (GA), a Grey wolf optimizer (GWO), a Water cycle algorithm (WCA), and Population base increment learning (PBIL) were used as ingredients of the proposed algorithm. The considered wing design problem is posed for overall weight minimization subject to several aeroelastic and structural constraints along with multiple discrete design variables to ascertain its viability for real-world applications. The algorithms are validated through the standard test functions of the CEC-RW-2020 test suite and composite Goland wing aeroelastic optimization. To check the performance, the proposed algorithm is contrasted with eight well established and newly developed MHs. Finally, a statistical analysis is done by performing Friedman’s rank test and allocating respective ranks to the algorithms. Based on the outcome, ithas been observed that the suggested algorithm outperforms the others
Additively manufactured polyethylene terephthalate scaffolds for Scapholunate Interosseous Ligament Reconstruction
The regeneration of the ruptured scapholunate interosseous ligament (SLIL)
represents a clinical challenge. Here, we propose the use of a
Bone-Ligament-Bone (BLB) 3D-printed polyethylene terephthalate (PET) scaffold
for achieving mechanical stabilisation of the scaphoid and lunate following
SLIL rupture. The BLB scaffold featured two bone compartments bridged by
aligned fibres (ligament compartment) mimicking the architecture of the native
tissue. The scaffold presented tensile stiffness in the range of 260+/-38 N/mm
and ultimate load of 113+/-13 N, which would support physiological loading. A
finite element analysis, using inverse finite element analysis for material
property identification, showed an adequate fit between simulation and
experimental data. The scaffold was then biofunctionalized using two different
methods: injected with a Gelatin Methacryloyl solution containing human
mesenchymal stem cell spheroids or seeded with tendon-derived stem cells and
placed in a bioreactor to undergo cyclic deformation. The first approach
demonstrated high cell viability, as cells migrated out of the spheroid and
colonised the interstitial space of the scaffold. These cells adopted an
elongated morphology suggesting the internal architecture of the scaffold
exerted topographical guidance. The second method demonstrated the high
resilience of the scaffold to cyclic deformation and the secretion of a
fibroblastic related protein was enhanced by the mechanical stimulation. This
process promoted the expression of relevant proteins, such as Tenomodulin,
indicating mechanical stimulation may enhance cell differentiation and be
useful prior to surgical implantation. In conclusion, the PET scaffold
presented several promising characteristics for the immediate mechanical
stabilisation of disassociated scaphoid and lunate and, in the longer-term, the
regeneration of the ruptured SLIL
Development of optical microchip sensor for biomolecule detection
Optical sensors play vital roles in many applications in today’s world. Photonic technologies used to design and engineer optical sensing platforms can provide distinctive advantages over conventional detection techniques. For instance, when compared to electronic and magnetic sensing systems, optical sensors require physically smaller equipment and have the capability for delivering more analytical information (e.g. spectroscopic signatures). In addition, demand for low-cost and portable bio-analyte detections is a growing area for applications in healthcare and environmental fields. Among other factors to achieve reliable results in terms of selectivity and sensitivity is key for the detection of bio-analytes with analytical relevance. Commonly used bio-analytical techniques (e. g. high performance liquid chromatography) have been appropriately designed based on qualitative and quantitative analysis. However, the requirement of expensive equipment, and complexity of procedures (e.g. biomolecule labelling, calibrations, etc.) restrict the board applicability and growth of these techniques in the field of biosensing. Optical sensors tackle these problems because they enable selective and sensitive detection of analytes of interest with label-free, real-time, and cost-effective processes. Among them, optical interferometry is increasingly popular due label-free detection, simple optical platforms and low-cost design. An ideal substrate with high surface area as well as biological/chemical stability against degradation can enable the development of advanced analytical tools with broad applicability. Nanoporous anodic alumina has been recently envisaged as a powerful platform to develop label-free optical sensors in combination with different optical techniques.
This thesis presents a high sensitive label-free biosensor design combining nanoporous anodic alumina (NAA) photonic structures and reflectometric interference spectroscopy (RIfS) for biomedical, food and agricultural applications. NAA is a suitable optical sensing platform due to its optical properties; a high surface area; its straightforward, scalable, and cost-competitive fabrication process, and its chemical and mechanical stability towards biological environments. Our biosensor enables real-time screening of any absorption and desorption event occurring inside the NAA pores. A proper selection of bio-analytes were able to be detected using this platform which offers unique feature in terms of simplicity and accuracy. The most relevant components of this thesis are categorised as below:
1. Self-ordered NAA fabrication and detection of an enzymatic analyte as a biomarker for cancer diagnosis: Fabrication of NAA photonic films using two step electrochemical anodization and chemical functionalisation. Detection of trace levels of analyte enzyme and its quantification by selective digestion. The NAA photonic film with the enzyme acts as a promising combination for a real-time point-of-care monitoring system for early stages of disease.
2. NAA rugate filters used to establish the binding affinity between blood proteins and drugs: Design, fabrication, and optimisation of NAA anodization parameters using sinusoidal pulse anodization approach (i.e. anodization offset and anodization period) to produce rugate filter photonic crystals that provide two comparative sensing parameters. Establishment of highly sensitive and selective device capable for drug binding assessments linked to treating a wide range of medical conditions.
3. NAA bilayers and food bioactive compound detection: Design, fabrication, and optimisation of NAA anodization parameters (i.e. anodization time and number of anodization steps) to obtain NAA bilayered photonic structures that display the effective response of NAA geometry with different types of nano-pore engineering. The photonic properties of the NAA bilayer were studied at each layer of nano-structure under specific binding of human serum albumin and quercetin as target agent. 4. Single nucleotide polymorphism (SNP) detection: The design and implementation of a Ligation-Rolling Circle Amplification assay to detect a single nucleotide polymorphism associated with insecticide resistance in a pest beetle species, Tribolium castaneum. This proof-of-concept SNP detection assay has the potential to provide a method compatible with a biosensor platform such as NAA. This demonstrates the first step towards the potential development of a genotyping biosensor, and a real-world application of insect insecticide resistance monitoring.
The results presented in this thesis are expected to enable innovative developments on NAA sensing technology that could result in highly sensitive and selective detection systems for a broad range of bio-analytes detections.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Chemical Engineering, 201
Optimal Design of Functionally Graded Parts
Several additive manufacturing processes are capable of fabricating three-dimensional parts with complex distribution of material composition to achieve desired local properties and functions. This unique advantage could be exploited by developing and implementing methodologies capable of optimizing the distribution of material composition for one-, two-, and three-dimensional parts. This paper is the first effort to review the research works on developing these methods. The underlying components (i.e., building blocks) in all of these methods include the homogenization approach, material representation technique, finite element analysis approach, and the choice of optimization algorithm. The overall performance of each method mainly depends on these components and how they work together. For instance, if a simple one-dimensional analytical equation is used to represent the material composition distribution, the finite element analysis and optimization would be straightforward, but it does not have the versatility of a method which uses an advanced representation technique. In this paper, evolution of these methods is followed; noteworthy homogenization approaches, representation techniques, finite element analysis approaches, and optimization algorithms used/developed in these studies are described; and most powerful design methods are identified, explained, and compared against each other. Also, manufacturing techniques, capable of producing functionally graded materials with complex material distribution, are reviewed; and future research directions are discussed
The Design and Assessment of Bio-Inspired Additive Manufactured Stab Resistant Armour
The performance of modern fibre-based or Polycarbonate armour has
significantly progressed since their introduction, providing protection against a
range of low and high velocity threats. While this is so, users of such armour
frequently report of issues relating to their operational suitability resulting in
impaired performance and physiological effects. Recently researchers have
focussed on how naturally occurring protective mechanisms could be utilised to
enhance the protective and operational performance of wearers of engineered
body armour. The research presented within this paper therefore utilises a series
of key design characteristics exhibited within naturally occurring elasmoid scale
armour, coupled with established Laser Sintering manufacturing parameters, for
the realisation and assessment of a scale-based stab resistant armoured structure
to internationally recognised test standards
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