scholarly journals Consolidation-Driven Defect Generation in Thick Composite Parts

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
J. P.-H. Belnoue ◽  
O. J. Nixon-Pearson ◽  
A. J. Thompson ◽  
D. S. Ivanov ◽  
K. D. Potter ◽  
...  
Keyword(s):  
Defect Formation ◽  
Numerical Models ◽  
Small Scale ◽  
The Novel ◽  
Fiber Waviness ◽  
Finite Element Software ◽  
Out Of Plane ◽  
Fiber Path ◽  
Typical Component

Fiber waviness is one of the most significant defects that occurs in composites due to the severe knockdown in mechanical properties that it causes. This paper investigates the mechanisms for the generation of fiber path defects during processing of composites prepreg materials and proposes new predictive numerical models. A key focus of the work was on thick sections, where consolidation of the ply stack leads to out of plane ply movement. This deformation can either directly lead to fiber waviness or can cause excess fiber length in a ply that in turn leads to the formation of wrinkles. The novel predictive model, built on extensive characterization of prepregs in small-scale compaction tests, was implemented in the finite element software abaqus as a bespoke user-defined material. A number of industrially relevant case studies were investigated to demonstrate the formation of defects in typical component features. The validated numerical model was used to extend the understanding gained from manufacturing trials to isolate the influence of various material, geometric, and process parameters on defect formation.

scholarly journals Mechanical Characterization of Timber-to-Timber Composite (TTC) Joints with Self-Tapping Screws in a Standard Push-Out Setup

2020 ◽  
Vol 10 (18) ◽  
pp. 6534
Author(s):  
Chiara Bedon ◽  
Martina Sciomenta ◽  
Massimo Fragiacomo
Keyword(s):  
Mechanical Characterization ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Small Scale ◽  
Load Bearing ◽  
Timber Constructions ◽  
Technical Interest ◽  
Push Out

Self-tapping screws (STSs) can be efficiently used in various fastening solutions for timber constructions and are notoriously able to offer high stiffness and load-carrying capacity, compared to other timber-to-timber composite (TTC) joint typologies. The geometrical and mechanical characterization of TTC joints, however, is often hard and uncertain, due to a combination of various influencing parameters and mechanical aspects. Among others, the effects of friction phenomena between the system components and their reciprocal interaction under the imposed design loads can remarkably influence the final estimates on structural capacity, in the same way of possible variations in the boundary conditions. The use of Finite Element (FE) numerical models is well-known to represent a robust tool and a valid alternative to costly and time consuming experiments and allows one to further explore the selected load-bearing components at a more refined level. Based on previous research efforts, this paper presents an extended FE investigation based on full three-dimensional (3D) brick models and surface-based cohesive zone modelling (CZM) techniques. The attention is focused on the mechanical characterization of small-scale TTC specimens with inclined STSs having variable configurations, under a standard push-out (PO) setup. Based on experimental data and analytical models of literature, an extended parametric investigation is presented and correlation formulae are proposed for the analysis of maximum resistance and stiffness variations. The attention is then focused on the load-bearing role of the steel screws, as an active component of TTC joints, based on the analysis of sustained resultant force contributions. The sensitivity of PO numerical estimates to few key input parameters of technical interest, including boundaries, friction and basic damage parameters, is thus discussed in the paper.

scholarly journals Overview of laser-driven generation of electron–positron beams

2015 ◽  
Vol 81 (4) ◽  
Author(s):  
G. Sarri ◽  
M. E. Dieckmann ◽  
I. Kourakis ◽  
A. Di Piazza ◽  
B. Reville ◽  
...  
Keyword(s):  
Plasma Physics ◽  
Numerical Models ◽  
Collective Effects ◽  
Small Scale ◽  
The Novel ◽  
Exotic State ◽  
Pair Plasma ◽  
Electron Positron ◽  
Laboratory Plasmas ◽  
The Universe

Electron–positron (e–p) plasmas are widely thought to be emitted, in the form of ultra-relativistic winds or collimated jets, by some of the most energetic or powerful objects in the Universe, such as black-holes, pulsars, and quasars. These phenomena represent an unmatched astrophysical laboratory to test physics at its limit and, given their immense distance from Earth (some even farther than several billion light years), they also provide a unique window on the very early stages of our Universe. However, due to such gigantic distances, their properties are only inferred from the indirect interpretation of their radiative signatures and from matching numerical models: their generation mechanism and dynamics still pose complicated enigmas to the scientific community. Small-scale reproductions in the laboratory would represent a fundamental step towards a deeper understanding of this exotic state of matter. Here we present recent experimental results concerning the laser-driven production of ultra-relativistic e–p beams. In particular, we focus on the possibility of generating beams that present charge neutrality and that allow for collective effects in their dynamics, necessary ingredients for the testing pair-plasma physics in the laboratory. A brief discussion of the analytical and numerical modelling of the dynamics of these plasmas is also presented in order to provide a summary of the novel plasma physics that can be accessed with these objects. Finally, general considerations on the scalability of laboratory plasmas up to astrophysical scenarios are given.

scholarly journals Accelerator-Based Nuclear Techniques for Processing and Characterization of Oxide Semiconductors for Solar Energy Conversion

2016 ◽  
Vol 253 ◽  
pp. 59-142
Author(s):  
Željko Pastuovic ◽  
Mihail Ionescu ◽  
Ettore Vittone ◽  
Ivana Capan
Keyword(s):  
Chemical Composition ◽  
Solar Energy ◽  
Energy Conversion ◽  
Defect Formation ◽  
Solar Energy Conversion ◽  
Ion Beams ◽  
Small Scale ◽  
Oxide Semiconductors ◽  
Nuclear Techniques

Accelerator-based nuclear techniques are an important tool for the modification and characterization of surfaces in general, down to a depth of around one micrometer. For oxide semiconductors used in solar energy conversion, the surface plays a critical role in facilitating the use of solar photon energy to obtain hydrogen via spontaneous water oxidation. For such a process, the required surface properties are complex and include specific chemical composition, as well as the defect composition, and both of these characteristics may be augmented using accelerator-based nuclear techniques. The targeted modification of surfaces makes use of ion implantation for changing the chemical composition, and ion irradiation for changing the defect structure. The defect formation is a very complex process, and in this work we placed more emphasis on this aspect. We attempted to present the defect formation under the irradiation of ion beams at the two extremes: formation of extensive and large-scale cluster defects; and formation of small-scale point defects. In addition, we review the main characterization techniques based on ion beams, with examples from work carried out on semiconductors and oxide semiconductors.

scholarly journals Multi-scale physico-chemical characterization of CEB/ANS bio-composites

2021 ◽  
Vol 348 ◽  
pp. 01008
Author(s):  
Hajar Akhzouz ◽  
Hassan El Minor ◽  
Amine Bendarma ◽  
Hanane El Minor
Keyword(s):  
Numerical Models ◽  
Chemical Characterization ◽  
Multi Scale ◽  
Finite Element Software ◽  
Physico Chemical ◽  
Heterogeneous Structures ◽  
Compressed Earth Blocks ◽  
Linear Behaviour ◽  
Earth Blocks

In a vision to identify the non-linear behaviour of the compressed earth blocks (CEB) reinforced by the Argan nut shells particles (ANS) influenced by many parameters like the shape, the distribution and the quantity of the stabilizers, as well as the interactions between both phases: matrix and reinforcement. The use of numerical models seems to be indispensable. Yet, simulations of heterogeneous structures quickly become unaffordable by direct calculations on finite element software. Therefore, a homogenization of the experimental, analytical, and numerical macrostructure is performed. Thus, an overall micro-mesomacro approach to modelling the mechanical behaviour of CEB/CNA bio-composites has been established. It is mainly based on the notion of the representative elementary volume with two different structures (periodic structure and structure with a poisson distribution). The numerical and analytical homogenization results were validated by the Young’s modulus values resulting from the experimental compression test and the corresponding stress-strain curves.

Optical and Chemical Characterization of Aerosols Emitted from Coal, Heavy and Light Fuel Oil, and Small-Scale Wood Combustion

2013 ◽  
Vol 48 (1) ◽  
pp. 827-836 ◽  
Author(s):  
Anna K. Frey ◽  
Karri Saarnio ◽  
Heikki Lamberg ◽  
Fanni Mylläri ◽  
Panu Karjalainen ◽  
...  
Keyword(s):  
Chemical Characterization ◽  
Fuel Oil ◽  
Small Scale ◽  
Wood Combustion

scholarly journals The Effectiveness of Ensemble-Neural Network Techniques to Predict Peak Uplift Resistance of Buried Pipes in Reinforced Sand

2021 ◽  
Vol 11 (3) ◽  
pp. 908
Author(s):  
Jie Zeng ◽  
Panagiotis G. Asteris ◽  
Anna P. Mamou ◽  
Ahmed Salih Mohammed ◽  
Emmanuil A. Golias ◽  
...  
Keyword(s):  
Neural Network ◽  
Numerical Models ◽  
Correlation Coefficients ◽  
Network Models ◽  
Small Scale ◽  
Offshore Platforms ◽  
Neural Network Models ◽  
Buried Pipes ◽  
Ensemble Techniques ◽  
Uplift Resistance

Buried pipes are extensively used for oil transportation from offshore platforms. Under unfavorable loading combinations, the pipe’s uplift resistance may be exceeded, which may result in excessive deformations and significant disruptions. This paper presents findings from a series of small-scale tests performed on pipes buried in geogrid-reinforced sands, with the measured peak uplift resistance being used to calibrate advanced numerical models employing neural networks. Multilayer perceptron (MLP) and Radial Basis Function (RBF) primary structure types have been used to train two neural network models, which were then further developed using bagging and boosting ensemble techniques. Correlation coefficients in excess of 0.954 between the measured and predicted peak uplift resistance have been achieved. The results show that the design of pipelines can be significantly improved using the proposed novel, reliable and robust soft computing models.

Characterization of the novel HLA‐C *07:944 allele by next‐generation sequencing

HLA ◽  
2021 ◽  
Author(s):  
Maria Loginova ◽  
Olga Makhova ◽  
Daria Smirnova ◽  
Igor Paramonov ◽  
Maksim Zarubin
Keyword(s):  
Next Generation Sequencing ◽  
The Novel ◽  
Next Generation ◽  
Generation Sequencing

Characterization of the novel HLA‐B *51:296 allele by next‐generation sequencing

HLA ◽  
2020 ◽  
Author(s):  
Steve Genebrier ◽  
Vincent Elsermans ◽  
Emeric Texeraud ◽  
Gerald Bertrand ◽  
Virginie Renac
Keyword(s):  
Next Generation Sequencing ◽  
The Novel ◽  
Next Generation ◽  
Generation Sequencing
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