scholarly journals Compressive behaviours of octet-truss lattices

2020 ◽  
Vol 234 (16) ◽  
pp. 3257-3269 ◽  
Author(s):  
Yifan Li ◽  
Huaiyuan Gu ◽  
Martyn Pavier ◽  
Harry Coules
Keyword(s):  
Failure Modes ◽  
Density Ratio ◽  
Three Dimensional ◽  
Compressive Load ◽  
High Strength ◽  
Detailed Comparison ◽  
Compressive Response ◽  
Beam Elements ◽  
Structural Applications ◽  
Octet Truss

Octet-truss lattice structures can be used for lightweight structural applications due to their high strength-to-density ratio. In this research, octet-truss lattice specimens were fabricated by stereolithography additive manufacturing with a photopolymer resin. The mechanical properties of this structure have been examined in three orthogonal orientations under the compressive load. Detailed comparison and description were carried out on deformation mechanisms and failure modes in different lattice orientations. Finite element models using both beam elements and three-dimensional solid elements were used to simulate the compressive response of this structure. Both the load reaction and collapse modes obtained in simulations were compared with test results. Our results indicate that three-dimensional continuum element models are required to accurately capture the behaviour of real trusses, taking into account the effects of finite-sized beams and joints.

Chemical Mechanical Surface Nano-Structuring (CMNS) Implementation on Titanium Based Implants to Enhance Corrosion Resistance and Control Biocompatibility

MRS Advances ◽  
2020 ◽  
Vol 5 (43) ◽  
pp. 2209-2219
Author(s):  
Kimberly Beers ◽  
Debashish Sur ◽  
G. Bahar Basim
Keyword(s):  
Cell Attachment ◽  
Density Ratio ◽  
Three Dimensional ◽  
High Strength ◽  
Surface Characteristics ◽  
Tissue Growth ◽  
Protective Oxide ◽  
Cardiac Pacemakers ◽  
Mechanical Surface

AbstractTitanium is the metal of choice for many implantable devices including dental prostheses, orthopaedic devices and cardiac pacemakers. Titanium and its alloys are favoured for hard tissue replacement because of their high strength to density ratio providing excellent mechanical properties and biocompatible surface characteristics promoting in-vivo passivation due to spontaneous formation of a native protective oxide layer in the presence of an oxidizer. This study focuses on the development of a three-dimensional chemical, mechanical, surface nano-structuring (CMNS) process to induce smoothness or controlled nano-roughness on the bio-implant surfaces, particularly for applications in dental implants. CMNS is an extension of the chemical mechanical polishing (CMP) process. CMP is utilized in microelectronics manufacturing for planarizing the wafer surfaces to enable photolithography and multilayer metallization. In biomaterials applications, the same approach can be utilized to induce controlled surface nanostructure on three-dimensional implantable objects to promote or demote cell attachment. As a synergistic method of nano-structuring on the implant surfaces, CMNS also makes the titanium surface more adaptable for the bio-compatible coatings as well as the cell and tissue growth as demonstrated by the electrochemical and surface wettability evaluations on implants prepared by DI-water machining versus oil based machining.

Experimental study on in-plane compressive response of irregular honeycombs

2017 ◽  
Vol 52 (8) ◽  
pp. 1121-1135
Author(s):  
Youming Chen ◽  
Raj Das ◽  
Mark Battley
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Mechanical Performance ◽  
Three Dimensional ◽  
Compressive Load ◽  
Neighbouring Cell ◽  
Deformation And Failure ◽  
Compressive Response ◽  
A Cell ◽  
Foam Mechanics

Compared with regular honeycombs, irregular honeycombs are more representative of real foams, and thus more suitable for the study of foam mechanics. In this paper, the deformation and failure progression in the irregular honeycombs are investigated by analysing the images captured in order to gain an improved understanding on foam failure. Irregular honeycombs with varying cell wall thickness, cell size and cell shape were manufactured using a three-dimensional printer and tested under compression. The behaviour of irregular honeycombs is found to be different from that of regular honeycombs. In irregular honeycombs, cell walls start to fracture at some point, initially at a low speed from multiple locations. The global stress reaches its maximum value shortly after the first fracture of cell walls. Only a few cell walls buckle in the specimens with cells of irregular shape. Fracture is more likely to occur to thin and long cell walls aligned within a medium angle (around 30 to 60°) to the compressive load. However, the susceptibility of a cell wall is to fracture is also affected by its neighbouring cell walls. Strong and stiff neighbouring cell walls could shield load away and protect it from breaking. Because of this, it is better to think of a weak spot as a region, rather than an individual cell or cell wall. Overall, the more uniform cell wall size and thickness are, the better the mechanical performance of cellular solids is.

Mechanical Reinforcement of Three-Dimensional Spacer Fabric Composites

2010 ◽  
Vol 654-656 ◽  
pp. 2604-2607 ◽  
Author(s):  
Shao Kai Wang ◽  
Min Li ◽  
Yi Zhuo Gu ◽  
Zuo Guang Zhang ◽  
Bo Ming Wu
Keyword(s):  
Failure Modes ◽  
Synergistic Effects ◽  
Three Dimensional ◽  
Compressive Load ◽  
Mechanical Reinforcement ◽  
The Core ◽  
Fabric Composite ◽  
Spacer Fabric ◽  
Fabric Composites ◽  
Foam Filling

Three-dimensional (3-D) spacer fabric composite is a novel lightweight sandwich structure, the reinforcement of which is integrally woven with two facesheets connected by continuous fibers (named piles) in the core. Usually the 3-D spacer fabric composite without extra reinforcement is called mono-spacer fabric composite, which provides outstanding facesheet / core debonding resistance. However, its mechanical properties cannot meet the demand of structure application because of the thin facesheet and low load-bearing capacity of high piles. Hence, two reinforcement methods were developed by laminating additional weaves at the facesheet and filling foam materials in the core to strengthen the facesheet and piles, respectively. This paper aims to investigate the influences of reinforcement methods on the mechanical behaviors and damage modes of 3-D spacer fabric composites under flatwise compressive, shear, edgewise compressive and three-point bending loads, by comparing with mono-spacer fabric composites. The results indicate that additional weaves reinforcement can enhance edgewise compressive and flexural properties effectively. Foam filling is one of the best options to improve the flatwise compressive and shear properties, and especially, there are synergistic effects between piles and foam under flatwise compressive load. Besides, the failure modes of reinforced and mono-spacer fabric composites are different.

Size effect on the shear capacity of headed studs

2020 ◽  
pp. 136943322096903
Author(s):  
Ahmet Abdullah Dönmez
Keyword(s):  
Size Effect ◽  
Failure Modes ◽  
Three Dimensional ◽  
High Strength ◽  
Shear Capacity ◽  
Microplane Model ◽  
Effect Factor ◽  
Shear Connectors ◽  
Concrete Damage ◽  
Damage Constitutive Model

This study aimed to reveal the existence of size effect on the shear connectors used in the steel-concrete composite beams and slabs. The experimental study contains the monotonic tests of nine pushout specimens with the headed studs. Three-dimensional scaling was used for geometrically similar specimens of three sizes. High strength concrete slabs were used on both sides of the steel I-beam. The failure modes of the specimens include both concrete crushing and stud yielding. Finite element (FE) verification of the specimens was conducted using a realistic concrete damage constitutive model, Microplane Model M7. It is shown that there may be a non-negligible size effect based on the fracture patterns of the composite member. Bažant’s size effect law (SEL) can fit the size effect behavior of the shear connectors. The design equations which do not include a size effect term have high correction factors that overestimate the tested specimens. A new design equation can be drawn using the size effect factor for strength reduction of shear connectors.

scholarly journals Novel Hybrid Polymer Composites with Graphene and MXene Nano-Reinforcements: Computational Analysis

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1013
Author(s):  
Sigitas Kilikevičius ◽  
Saulė Kvietkaitė ◽  
Leon Mishnaevsky ◽  
Mária Omastová ◽  
Andrey Aniskevich ◽  
...  
Keyword(s):  
Polymer Composites ◽  
Flexible Electronics ◽  
Computational Analysis ◽  
Structural Integrity ◽  
Three Dimensional ◽  
High Strength ◽  
Hybrid Polymer ◽  
Damage Behavior ◽  
Future Design ◽  
Structural Applications

This paper presents a computational analysis on the mechanical and damage behavior of novel hybrid polymer composites with graphene and MXene nano-reinforcements targeted for flexible electronics and advanced high-strength structural applications with additional functions, such as real-time monitoring of structural integrity. Geometrical models of three-dimensional representative volume elements of various configurations were generated, and a computational model based on the micromechanical finite element method was developed and solved using an explicit dynamic solver. The influence of the geometrical orientation, aspect ratio, and volume fractions of the inclusions, as well as the interface properties between the nano-reinforcements and the matrix on the mechanical behavior, was determined. The results of the presented research give initial insights about the mechanical and damage behavior of the proposed composites and provide insight for future design iterations of similar multifunctional materials.

In Situ Investigation of Microstructural Changes in Thermoplastic Composite Pipe Under Compressive Load

2014 ◽  
Author(s):  
Neville Dodds ◽  
Ketan Pancholi ◽  
Vineet Jha ◽  
Syed Fawad Tariq ◽  
James Latto
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Failure Modes ◽  
Three Dimensional ◽  
Compressive Load ◽  
Thermoplastic Composite ◽  
In Situ Observation ◽  
Stress Strain ◽  
In Situ Investigation

Thermoplastic composite materials are very advantageous as component layers in subsea risers due to their inherent properties such as high strength, low density, fatigue and chemical resistance. However, response of composite materials to applied loading is complex and three-dimensional in nature. The heterogeneous structure of the composite material induces irregular distribution of stress/strain over the cross-section and thus, it is essential for design to use analytical methods capable of determining the stress-strain relationship in three-dimensional space. Currently, most methods rely upon one-dimensional or two-dimensional data collection techniques with macro scale stress / strain observations for experimental validation. In order to ascertain the correct load to the failure, a complete understanding of the material failure at the micro-scale is essential. In this work, X-ray computed tomography is employed for the in situ observation of micromechanical failure of the composite material under a compressive load. The observed results are compared and validated with the traditional stress-strain data and finite element analysis. It is observed that the damage in the composite material initiates by delamination which grows as the loading progresses. Moreover, the properties and failure modes are highly dependent on the manufacturing process. By gaining further understanding of the failure modes using these methods, the findings can be utilized in optimizing the design of composite riser structures.

scholarly journals Finite Element Model of Composite Connections Strengthened with CFRP Laminates

2019 ◽  
Author(s):  
Mahyar Ramezani
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Weight Ratio ◽  
High Strength ◽  
Element Model ◽  
Cfrp Laminates ◽  
Cfrp Sheets ◽  
Structural Applications ◽  
The Moment ◽  
Composite Connections

Carbon Fiber Reinforced Polymer (CFRP) materials are being widely used for structural applications. Despite the relatively high cost of the CFRP materials, their high strength-to-weight ratio and corrosion resistance as well as easy handling and installation have made them widely popular for different civil engineering applications where increased strength and/or ductility is important. This thesis investigates the moment-rotational response of an endplate composite connection including strengthening of the slab by using different sizes and thickness of CFRP sheets in hogging moment regions and different reinforcement bar ratios by using finite element simulations. A three dimensional non-linear model is developed in ANSYS to study the feasibility of decreasing the reinforcing bars in the presence of the CFRP laminate in hogging moment regions of the slab. The verification of the analysis is carried out to calibrate the un-strengthened model by available experimental results obtained from a series of composite connection tests as reported by other researchers. The moment resistance for the partial depth endplate composite connection obtained by ANSYS 12.1 software is found to be very close to the corresponding laboratory test value. From the results it can be observed that applying CFRP sheets to the tension face of composite slab can reduce the amount of steel reinforcement bars required for flexural strength of composite connections.

Scanning Electron Microscopy in Hybrid Microelectronics

1976 ◽  
Vol 34 ◽  
pp. 456-457
Author(s):  
S. Khadpe ◽  
R. Faryniak
Keyword(s):  
Integrated Circuits ◽  
Thick Film ◽  
Integrated Circuit ◽  
Failure Modes ◽  
Three Dimensional ◽  
Circuit Components ◽  
Hybrid Microcircuit ◽  
Electrical Connections ◽  
Scanning Electron

The Scanning Electron Microscope (SEM) is an important tool in Thick Film Hybrid Microcircuits Manufacturing because of its large depth of focus and three dimensional capability. This paper discusses some of the important areas in which the SEM is used to monitor process control and component failure modes during the various stages of manufacture of a typical hybrid microcircuit.Figure 1 shows a thick film hybrid microcircuit used in a Motorola Paging Receiver. The circuit consists of thick film resistors and conductors screened and fired on a ceramic (aluminum oxide) substrate. Two integrated circuit dice are bonded to the conductors by means of conductive epoxy and electrical connections from each integrated circuit to the substrate are made by ultrasonically bonding 1 mil aluminum wires from the die pads to appropriate conductor pads on the substrate. In addition to the integrated circuits and the resistors, the circuit includes seven chip capacitors soldered onto the substrate. Some of the important considerations involved in the selection and reliability aspects of the hybrid circuit components are: (a) the quality of the substrate; (b) the surface structure of the thick film conductors; (c) the metallization characteristics of the integrated circuit; and (d) the quality of the wire bond interconnections.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

ALCOA 2024

Alloy Digest ◽  
1998 ◽  
Vol 47 (3) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Surface Treatment ◽  
Tensile Properties ◽  
Surface Finish ◽  
High Strength ◽  
Machined Surface ◽  
2024 Alloy ◽  
Structural Applications ◽  
Strength Material

Abstract Alcoa 2024 alloy has good machinability and machined surface finish capability, and is a high-strength material of adequate workability. It has largely superseded alloy 2017 (see Alloy Digest Al-58, August 1974) for structural applications. The alloy has comparable strength to some mild steels. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on corrosion resistance as well as machining and surface treatment. Filing Code: AL-346. Producer or source: ALCOA Wire, Rod & Bar Division.

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