Material Selection for CFRP-Aluminium-Foam-Sandwiches Manufactured by a PUR Spraying Process

2017 ◽  
Vol 742 ◽  
pp. 317-324
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay André Weidenmann
Keyword(s):  
Manufacturing Process ◽  
Sandwich Structures ◽  
Bending Stiffness ◽  
Effective Density ◽  
Sandwich Composites ◽  
Open Cell ◽  
The Core ◽  
Bending Modulus ◽  
The Face ◽  
Spraying Process

Sandwich structures are ideal for planar parts which require a high bending stiffness ata low weight. Usually, sandwich structures are manufactured using a joining step, connecting theface sheets with the core. The PUR spraying process allows to include the infiltration of the facesheet fibres, the curing of the matrix and the joining of the face sheets to the core within one processstep. Furthermore, this manufacturing process allows for the use of open cell core structures withoutinfiltrating the core, which enables a comparison of different material configurations, assembled bythe same manufacturing process. The selection of these materials, with the aim of the lowest possiblemass of the sandwich composite at a constant bending stiffness, is displayed systematically within thiswork.It could be shown that the bending modulus calculated from the component properties matched theexperimentally achieved values well, with only few exceptions. The optimum of the bending modulus,the face sheet thickness and the resulting effective density could be calculated and also matched theexperimental values well. The mass-specific bending stiffness of the sandwich composites with corestructures of open cell aluminium foams was higher than with closed cell aluminium foams, but wasexceeded by sandwich composites with Nomex honeycomb cores.

Failure mode maps for four-point-bending of hybrid sandwich structures with carbon fiber reinforced plastic face sheets and aluminum foam cores manufactured by a polyurethane spraying process

2017 ◽  
Vol 21 (8) ◽  
pp. 2654-2679 ◽  
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay A Weidenmann
Keyword(s):  
Carbon Fiber ◽  
Failure Mode ◽  
Aluminum Foam ◽  
Failure Modes ◽  
Sandwich Panels ◽  
Bending Tests ◽  
The Core ◽  
Four Point Bending ◽  
The Face ◽  
Spraying Process

This work focuses on failure mode maps of sandwich panels exposed to bending load, which were produced using a polyurethane spraying process. This process allows for an automated production of sandwich panels omitting a separate bonding step of the face sheets to the core. The investigated sandwich panels consisted of carbon fiber reinforced face sheets in various configurations, and four different core structures of aluminum foam or Nomex honeycomb. After production, measurements of the pores inside the core foam structures, the fiber package thickness inside the face sheets, and the density homogeneity of the core structure were made using X-ray computed tomography. The failure mode maps were based on the individual mechanical properties of the face sheets and the core, determined by mechanical testing. The critical forces determining the failure modes were partially modified to fit the application on foam core structures and face sheets with a porous matrix. The verification of the failure modes was performed with four-point bending tests. Since all tested configurations of sandwich specimens were produced using the same process route, the applied models for the creation of the failure mode maps could be verified for numerous parameter combinations. Except for two parameters with inconstant properties, the failure modes determined by the failure mode maps matched the observed failure modes determined by the bending tests.

The effect of local bending stiffness on the wrinkling of sandwich panels

2003 ◽  
Vol 217 (2) ◽  
pp. 111-119
Author(s):  
L Fagerberg
Keyword(s):  
Elastic Modulus ◽  
Sandwich Panel ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Bending Stiffness ◽  
Face Sheet ◽  
Stacking Sequence ◽  
The Core ◽  
The Face

The use of the face sheet elastic modulus versus the face sheet local bending stiffness while designing against wrinkling is discussed in this paper. It shows that there are several ways to improve the critical wrinkling load of a sandwich panel without replacing the core. It is often possible to increase the wrinkling load by as much as 25 per cent without virtually any increase in weight or cost of the sandwich. This is achieved by improving the local bending stiffness of the sandwich face sheet by either optimizing the stacking sequence, lowering the fibre volume fraction or adding some extra layers of a cheap fibre material to the sandwich face, creating a minisandwich within the face sheet. Experiments are performed that clearly show the potential for increasing the critical wrinkling load by means of altering the face sheet.

Implication of Nonclassical Effects on Dynamic Response of Sandwich Structures Exposed to Underwater and In-Air Explosions

2007 ◽  
Vol 51 (02) ◽  
pp. 83-93
Author(s):  
Liviu Librescu ◽  
Sang-Yong Oh ◽  
Jorg Hohe
Keyword(s):  
Dynamic Response ◽  
Structural Model ◽  
Sandwich Structures ◽  
Damping Ratio ◽  
Sandwich Panels ◽  
Geometric Imperfection ◽  
The Core ◽  
The Face ◽  
Time Histories ◽  
Global And Local

A study devoted to the dynamic response of sandwich panels to underwater and in-air explosions is presented. The study is carried out in the context of a geometrically nonlinear model of sandwich structures featuring anisotropic laminated face sheets and a transversely compressible orthotropic core. The unsteady pressure generated by the explosion and acting on the face of the sandwich panel includes the effect of the pressure wave transmission through the core. Its implications on the structural time-histories as corresponding to the underwater and in-air explosions are put into evidence. The effects of the transverse core compressibility on dynamic response are highlighted. In this sense, one of its major implications is the possibility to capture interactively the global and local (wrinkling) dynamic response of the panel. It is shown that implementation of the structural tailoring technique in the face sheets can constitute an important mechanism for enhancing the dynamic load-carrying capacity of sandwich panels when exposed to blast pulses. Effects of the core, the composite architecture of face sheets, orthotropy of the material of the core, geometrical non-linearities, initial geometric imperfection, and the damping ratio are investigated, and their implications for the dynamic response are highlighted. The comprehensive structural model considered in conjunction with the time-dependent loads generated by the underwater and in-air explosions, and the results obtained in this context, are expected to contribute to a better understanding of the response behavior and to be instrumental toward a better design of these structures.

Impact Damage Resistance of Thin-Core Sandwich Structures Subjected to Low-Velocity Impact

2014 ◽  
Vol 684 ◽  
pp. 176-181
Author(s):  
Kai Lun Wang ◽  
Zhi Dong Guan ◽  
Jun Guo ◽  
Zeng Shan Li
Keyword(s):  
Sandwich Structures ◽  
Impact Damage ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Damage Resistance ◽  
Velocity Impact ◽  
The Core ◽  
The Face ◽  
The Impact ◽  
Impact Damages

This paper aims at evaluating the damage resistance of thin core sandwich structures, composed of aramid paper honeycomb core and carbon/ epoxy laminates face-sheets subjected to low velocity impact. The impact tests are performed using the instrumented impact-testing machine and resulting impact damages are inspected by Ultrasonic C-scan. In order to study the failure process of the core, which is important in the damage of the structures, flatwise compression test was carried out. Four parameters have been analyzed as follows: maximum load, total energy absorbed during impact, impact dent depth, and impact damage area. Nearly all impact force histories of panels have “twin peaks”, but the second peak of the 3mm-core structure is much larger than the first, which is quite different from others, when impact energy reached 5J, which were caused by the thickness of the core. Impact damages of thin-core sandwich structures are mainly delamination in the face-sheet and core crushing at low energy, and fiber breakage at relatively high energy. The damage processes of different groups of structures are essentially different and the impact resistance of the sandwich structure is greatly influenced by the face-sheet and core thickness.

Damage behavior of potting materials in sandwich composites with pinned joints

2015 ◽  
Vol 22 (5) ◽  
Author(s):  
Cesim Atas ◽  
Alper Basmaci
Keyword(s):  
Core Material ◽  
Sandwich Composite ◽  
Composite Panels ◽  
Sandwich Composites ◽  
Resin Infusion ◽  
Damage Behavior ◽  
Mechanical Joints ◽  
The Core ◽  
Bottom Face ◽  
Infusion Technique

AbstractThe damage behavior of the potting materials around a pinhole, being used in the mechanical joints of sandwich composites, is investigated experimentally. The sandwich composite panels used in the tests were manufactured by the vacuum-assisted resin infusion technique. Each of the top and bottom face sheets of the panels consisted of two woven E-glass/epoxy layers. As the core material, PVC foam (AIREX

Devolution processes and the theory of historical development by S. Sanderson

2021 ◽  
pp. 72-77
Author(s):  
A.V. Verkhoturov ◽  
◽  
A.A. Obukhov
Keyword(s):  
Historical Development ◽  
World System ◽  
Human Society ◽  
Evolutionary Trend ◽  
The Core ◽  
The World ◽  
The Face ◽  
American Historian ◽  
Immanuel Wallerstein ◽  
Main Ideas

Analyzed is one of the most comprehensive modern approaches to the problem of the existence of evolution of human society as such and of specific human communities, i.e. “General Theory of Historical Development” by American historian and sociologist Stephen Sanderson. While agreeing, in general, with its main ideas, we believe that it is important to note that the issue of existence of individual communities demonstrating devolution (regression to an earlier historical state), stagnation or degeneration at certain historical stages is practically ignored in the framework of the theory under consideration. This creates its vulnerability in the face of specific empirical data, indicating a deviation from the evolutionary trend. We believe that overcoming this theoretical difficulty is possible in the process of comprehending the theory of S. Sanderson in the context of ideas of the world-system approach of Immanuel Wallerstein. We want to show that examples of devolution, stagnation and degeneration of societies do not deny general progressive evolutionary tendencies, characteristic for the world-system as a whole, but only indicate the transition of a particular society to a lower level within the world-system (from the core to the semi-periphery, or from the semi-periphery to the periphery).

scholarly journals Impact Properties of Aluminum Foam – Nanosilica Filled Basalt Fiber Reinforced Polymer Sandwich Composites

2018 ◽  
Vol 7 (3.11) ◽  
pp. 77
Author(s):  
Nurul Emi Nor Ain Mohammad ◽  
Aidah Jumahat ◽  
Mohamad Fashan Ghazali
Keyword(s):  
Energy Absorption ◽  
Basalt Fiber ◽  
Sandwich Composite ◽  
Sandwich Composites ◽  
Basalt Fibre ◽  
Reinforced Polymer ◽  
Closed Cell ◽  
The Face ◽  
Al Foam ◽  
Fibre Reinforced Polymer

This paper investigates the effect of nanosilica on impact and energy absorption properties of sandwich foam-fibre composites. The materials used in this study are closed-cell aluminum (Al) foam (as the core material) that is sandwiched in between nanomodified basalt fiber reinforced polymer (as the face-sheets). The face sheets were made of Basalt Fibre, nanosilica and epoxy polymer matrix. The sandwich composite structures are known to have the capability of resisting impact loads and good in absorbing energy. The objective of this paper is to determine the influence of closed-cell aluminum foam core and nanosilica filler on impact properties and fracture behavior of basalt fibre reinforced polymer (BFRP) sandwich composites when compared to the conventional glass fibre reinforced polymer (GFRP) sandwich composites. The drop impact tests were carried out to determine the energy absorbed, peak load and the force-deflection behaviour of the sandwich composite structure material. The results showed that the nanomodified BFRP-Al foam core sandwich panel exhibited promising energy absorption properties, corresponding to the highest specific energy absorption value observed. Also, the result indicates that the Aluminium Foam BFRP sandwich composite exhibited higher energy absorption when compared to the Aluminium foam GFRP sandwich composite.  

scholarly journals Public Space as a Venue for Peacebuilding in Lebanon? The Role of Civic Movements in Reclaiming Public Space in Beirut and Tripoli

2021 ◽  
pp. 25-46
Author(s):  
Aseel Naamani ◽  
Ruth Simpson
Keyword(s):  
Public Space ◽  
Public Life ◽  
Public Spaces ◽  
Urban Spaces ◽  
Building Relationships ◽  
The Core ◽  
The Face ◽  
History Of ◽  
Post War

The issue of public spaces is increasingly at the core of civic movements and discourse of reform in Lebanon, coming to the fore most recently in the mass protests of October 2019. Yet, these most recent movements build on years of activism and contestation, seeking to reclaim rights to access and engage with public spaces in the face of encroachments, mainly by the private sector. Urban spaces, including the country’s two biggest cities – Beirut and Tripoli – have been largely privatised and the preserve of an elite few, and post-war development has been marred with criticism of corruption and exclusivity. This article explores the history of public spaces in Beirut and Tripoli and the successive civic movements, which have sought to realise rights to public space. The article argues that reclaiming public space is central to reform and re-building relationships across divides after years of conflict. First, the article describes the evolution of Lebanon’s two main urban centres. Second, it moves to discuss the role of the consociational system in the partition and regulation of public space. Then it describes the various civic movements related to public space and examines the opportunities created by the October 2019 movement. Penultimately it interrogates the limits imposed by COVID-19 and recent crises. Lastly, it explores how placemaking and public space can contribute to peacebuilding and concludes that public spaces are essential to citizen relationships and inclusive participation in public life and affairs.

Wave Propagation and Power Flow Analysis of Sandwich Structures With Internal Absorbers

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
J. S. Chen ◽  
R. T. Wang
Keyword(s):  
Wave Propagation ◽  
Power Flow ◽  
Wave Attenuation ◽  
Sandwich Structures ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Continuum Models ◽  
Sandwich Beams ◽  
The Core ◽  
In Series

This study examines wave attenuation and power flow characteristics of sandwich beams with internal absorbers. Two types of absorbing systems embedded in the core are considered, namely, a conventional spring-mass-dashpot system having a mass with a spring and a dashpot in parallel, and a relaxation system containing an additional relaxation spring added in series with the dashpot. Analytical continuum models used for interpreting the attenuation behavior of sandwich structures are presented. Through the analysis of the power flowing into the structure, the correlation of wave attenuation and energy blockage is revealed. The reduction in the power flow indicates that some amount of energy produced by the external force can be effectively obstructed by internal absorbers. The effects of parameters on peak attenuation, bandwidth, and power flow are also studied.

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