scholarly journals Evaluation of in-plane compressive densification strain of honeycomb paperboard

2020 ◽  
Vol 12 (4) ◽  
pp. 168781402091342
Author(s):  
Xin-ni Mou ◽  
Li-xin Lu ◽  
Yun-ling Zhou
Keyword(s):  
Energy Absorption ◽  
Critical Role ◽  
Absorption Efficiency ◽  
Compression Tests ◽  
Machine Direction ◽  
Load Bearing ◽  
Face Layer ◽  
Cross Direction ◽  
The Core ◽  
The Face

The compressive densification strain of honeycomb paperboard is one of the important parameters which affect the energy absorption property of honeycomb paperboard. The in-plane bearing mechanism of honeycomb paperboard in plastic zone was analyzed based on compression tests of the single row and multi-rows of honeycomb paperboard. The result indicates that the core layer plays a supporting role in resisting the buckling of the face layer. The double inner folds are formed in machine direction and the symmetrical inner folds are formed in cross direction in a honeycomb core. The core single wall and the face layer play a critical role in the load bearing in machine direction, and the core double walls, core single wall, and face layer all play critical roles in the load bearing in cross direction. On this basis, the evaluation equation of the compressive densification strain was obtained based on the energy absorption efficiency method and geometric scale effect, which are verified so that the experiment and test results are in good agreement.

Effect of Core Plasticity on the Post-Buckling Behavior of Debonded Sandwich Beams

2000 ◽  
Author(s):  
Bhavani V. Sankar ◽  
Manickam Narayanan ◽  
Abhinav Sharma
Keyword(s):  
Plastic Material ◽  
Maximum Load ◽  
Face Sheet ◽  
Compression Tests ◽  
Element Analysis ◽  
The Core ◽  
Perfectly Plastic ◽  
The Face ◽  
Post Buckling ◽  
Elastic Perfectly Plastic

Abstract Nonlinear finite element analysis was used to simulate compression tests on sandwich composites containing debonded face sheets. The core was modeled as an elastic-perfectly-plastic material, and the face-sheet as elastic isotropic. The effects of core plasticity, face-sheet and core thickness, and debond length on the maximum load the beam can carry were studied. The results indicate that the core plasticity is an important factor that determines the maximum load.

scholarly journals Compressive Behavior of Al-TiB2 Composite Foams Fabricated under Increased Pressure

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5112
Author(s):  
Yang Yu ◽  
Zhuokun Cao ◽  
Jiaqi Wang ◽  
Ganfeng Tu ◽  
Yongliang Mu
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Energy Absorption ◽  
Absorption Efficiency ◽  
Compression Tests ◽  
Cell Size Distribution ◽  
Size Refinement ◽  
Composite Foams ◽  
Stress Fluctuation ◽  
Increased Pressure

The application of increased pressure was used as a strategy to investigate the effect of different cell structures on the mechanical properties of Al-TiB2 composite foams. In situ Al-xTiB2 (x = 5, 10 wt.%) composites were foamed under three different pressures (0.1 MPa, 0.24 MPa, 0.4 MPa) through the liquid melt route. The macro-structure of the composite foams was analyzed in terms of cell size distribution measured by X-ray microcomputed tomography (micro-CT). It was found that the mean cell size decreases, and the cell size distribution range narrows with increasing pressure. Uniaxial compression tests revealed that the stress fluctuation (Rsd) of 10TiB2 foams is larger than that of 5TiB2 foams under the same pressure. Moreover, cell size refinement causes the simultaneous deformation of multi-layer cells, which leads to an enhancement in the energy absorption efficiency and specific energy absorption. The comparison of experimental data with theoretical predictions (G&A model) is discussed.

Quasi-static indentation and sound-absorbing properties of 3D printed sandwich core panels

2021 ◽  
pp. 109963622110370
Author(s):  
Guo Dong Goh ◽  
Song Jiang Casper Neo ◽  
Vishwesh Dikshit ◽  
Wai Yee Yeong
Keyword(s):  
Energy Absorption ◽  
Acoustic Properties ◽  
Face Sheet ◽  
Acoustic Absorption ◽  
Low Frequencies ◽  
The Core ◽  
Horizontal Beam ◽  
Static Indentation ◽  
Acoustic Absorption Coefficient ◽  
The Face

The use of 3D printing to produce acoustic panels with good mechanical and acoustic properties was investigated in this paper. Various fiber layups of the fiberglass face sheet and core designs were fabricated and tested for their indentation resistance and acoustic absorption performance. It was found that the bidirectional face sheet layup exhibited the best indentation energy absorption recording 4.2 J, which is 37% more than the 45-degree layout and 66% more than the quasi-isotropic layup. The specific energy absorption of the hybrid honeycomb core is the best among the three core designs recording 404 J/kg, which is 56% higher than the corrugated triangle with horizontal beam core (359 J/kg) and 20% higher than double ellipse core (335 J/kg). Computed-Tomography (CT) scan was used to study the fracture behavior of the sandwich structures. It was found that the bidirectional layup exhibited a different failure mode as compared to the 45-degree and quasi-isotropic layup. In terms of the acoustic properties, the face sheets with various layup patterns have a low acoustic absorption coefficient with minimal differences from each other at low frequencies (500 Hz–3000 Hz) and have higher absorption coefficients with greater differences from each other at frequencies between 3000 Hz–6500 Hz. The absorption curve was significantly affected by the design of the core. The orientation of the core also comes into play if the core is asymmetrical. The hybrid honeycomb sandwich structure was the optimal structure among the three designs for balanced indentation resistance and acoustic insulation.

scholarly journals Investigation and Statistical Evaluation of Reinforced Aluminum Foams

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 315
Author(s):  
Ivana Bunjan ◽  
Krešimir Grilec ◽  
Danko Ćorić
Keyword(s):  
Energy Absorption ◽  
Specific Energy ◽  
Steel Wire ◽  
Matrix Material ◽  
Absorption Efficiency ◽  
Compression Tests ◽  
Aluminum Foams ◽  
Specific Energy Absorption ◽  
Steel Mesh ◽  
Semi Solid

In this study, aluminum foams reinforced with different steel elements were produced by the AluLight process. The master alloy AlMgSi0.6 was used as the matrix material, titanium hydride (TiH2) powder was used as a foaming agent, and steel wire, cylindrical steel mesh and flat steel mesh were used as reinforcing elements. Reinforcements were placed inside the mold, along with the precursors, and samples were manufactured by gas releasing particles in a semi-solid state. To examine the effect of the reinforcements on specific energy absorption, quasi-static uniaxial compression tests were carried out, with a constant separation rate of 1 mm/s. From the tested results, the energy absorption per unit volume and specific energy absorption efficiency were calculated and then also statistically evaluated. The results showed that examined shapes of reinforcements affect differently specific energy absorption and its efficiency, compared to non-reinforced aluminum foams. The best result obtained was with cylindrically shaped steel mesh.

scholarly journals The energy absorption behavior of novel composite sandwich structures reinforced with trapezoidal latticed webs

2021 ◽  
Vol 60 (1) ◽  
pp. 503-518
Author(s):  
Juan Han ◽  
Lu Zhu ◽  
Hai Fang ◽  
Jian Wang ◽  
Peng Wu
Keyword(s):  
Bearing Capacity ◽  
Energy Absorption ◽  
Sandwich Structure ◽  
Ultimate Load ◽  
Sandwich Structures ◽  
Elastic Displacement ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Composite Sandwich ◽  
Composite Sandwich Structures

Abstract This article proposed an innovative composite sandwich structure reinforced with trapezoidal latticed webs with angles of 45°, 60° and 75°. Four specimens were conducted according to quasi-static compression methods to investigate the compressive behavior of the novel composite structures. The experimental results indicated that the specimen with 45° trapezoidal latticed webs showed the most excellent energy absorption ability, which was about 2.5 times of the structures with vertical latticed webs. Compared to the traditional composite sandwich structure, the elastic displacement and ultimate load-bearing capacity of the specimen with 45° trapezoidal latticed webs were increased by 624.1 and 439.8%, respectively. Numerical analysis of the composite sandwich structures was carried out by using a nonlinear explicit finite element (FE) software ANSYS/LS-DYNA. The influence of the thickness of face sheets, lattice webs and foam density on the elastic ultimate load-bearing capacity, the elastic displacement and initial stiffness was analyzed. This innovative composite bumper device for bridge pier protection against ship collision was simulated to verify its performance. The results showed that the peak impact force of the composite anti-collision device with 45° trapezoidal latticed webs would be reduced by 17.3%, and the time duration will be prolonged by about 31.1%.

Evaluation on the performance fluctuation after water ingestion for a turbofan engine compressor during flight descent

2020 ◽  
pp. 095441002097798
Author(s):  
Lu Yang ◽  
Qun Zheng ◽  
Aqiang Lin
Keyword(s):  
Droplet Diameter ◽  
Pressure Ratio ◽  
Critical Role ◽  
Water Film ◽  
Heavy Rain ◽  
Diameter Distribution ◽  
Turbofan Engine ◽  
Water Ingestion ◽  
The Core ◽  
Engine Compressor

Turbofan engine compressor is most severely threatened by the entry of liquid water during flight descent. This study aims to deeply understand the fluctuations of compressor performance parameters caused by water ingestion through frequency spectrum analysis. The water content and droplet diameter distribution are determined based on the real heavy rain environment. Results reveal that most of the droplets actually entering the core compressor have a particle size of less than 100 μm. In addition, the formation and motion of water film plays a critical role in affecting the fluctuation characteristics. Water ingestion deteriorates the compression performance and aggravates the unsteady fluctuations of the fan. However, the performance of the core compressor is less affected by water ingestion, but their fluctuations are still exacerbated. For some important parameters, such as inlet mass flow rate, total pressure ratio, total temperature ratio, compression work and efficiency, their main frequency of fluctuation are switched from the original blade passing frequency to the rotor passing frequency, and their amplitudes are correspondingly amplified to varying degrees. These phenomena can be observed in both the fluctuations of the fan and core compressor. Moreover, the operating point of them will be in the long-period and large-amplitude fluctuations, which leads them experiences the non-optimal state for a long time and threatens their operating stability.

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.

Fabrication of Bulk Functionally-Graded Syntactic Foams for Impact Energy Absorption

2012 ◽  
Vol 706-709 ◽  
pp. 711-716 ◽  
Author(s):  
Tadaharu Adachi ◽  
Masahiro Higuchi
Keyword(s):  
Theoretical Analysis ◽  
Energy Absorption ◽  
Functionally Graded ◽  
Fabrication Process ◽  
Syntactic Foams ◽  
Compression Tests ◽  
Matrix Resin ◽  
Local Fracture ◽  
Density Distributions ◽  
The Matrix

Function of functionally-graded (FG) foams as energy absorption material for impact was discussed on the basis of theoretical analysis, and fabrication process of the foams was proposed in the paper. The FG foams were found to be useful as impact absorber due to progressively local fracture or cushion in the theoretical analysis. Next the fabrication process of the FG foams was suggested. The graded dispersion of the micro-balloons was conducted before curing the matrix resin in the process. The density distributions in the FG foams were confirmed to be predicted by the numerical analysis on the basis of floating the micro-balloons. Finally, compression tests were carried out to evaluate mechanical properties.

scholarly journals A Tocqueville For the North? André Siegfried and Canada

2005 ◽  
Vol 14 (1) ◽  
pp. 117-136 ◽  
Author(s):  
Sean Kennedy
Keyword(s):  
Critical Role ◽  
Second World War ◽  
Traditional Values ◽  
French Canada ◽  
The North ◽  
Vichy Regime ◽  
The Face ◽  
A Site ◽  
French National Identity ◽  
Second World

Abstract This paper argues that André Siegfried’s writings on Canada played a critical role in shaping his vision of French national identity. Siegfried’s studies of Canada have long been praised for their insight, but recent scholarship has emphasized his role in promoting both anti-Americanism and an exclusionary vision of what it meant to be French during the first half of the twentieth century. For Siegfried, Canada represented a site of managed contestation between British and French culture but also an early example of the deleterious effects of Americanization. His problematic view of French Canada as essentially conservative and unchanging in the face of such challenges reinforced his conviction that France itself should remain true to “traditional” values. The exclusionary implications of his ideas were most evident when Siegfried appeared to accommodate himself to the Vichy regime, but they also persisted after the Second World War.

Revising the Assumption that Ḥadīṯ Studies Flourished in the 11th/17th-Century Ḥiǧāz: Ibrāhīm al-Kūrānī’s (d. 1101/1690) Contribution

Arabica ◽  
2021 ◽  
Vol 68 (1) ◽  
pp. 1-35
Author(s):  
Naser Dumairieh
Keyword(s):  
General Framework ◽  
18Th Century ◽  
Critical Role ◽  
17Th Century ◽  
Main Interest ◽  
Islamic World ◽  
The Core ◽  
Revival Movement ◽  
Almost All

Abstract The Ḥiǧāz in the 11th/17th century has long been considered the center of a “revival” movement in ḥadīṯ studies. This assumption has spread widely among scholars of the 11th-/17th- and 12th-/18th-century Islamic world based on the fact that the isnāds of many major ḥadīṯ scholars from almost all parts of the Islamic world from the 11th/17th century onward return to a group of scholars in the Ḥiǧāz. The scholarly group that is assumed to have played a critical role in the flourishing of ḥadīṯ studies in the 11th/17th-century Ḥiǧāz is called the al-Ḥaramayn circle or network. However, to date, there have been no studies that investigate what was actually happening in that century concerning ḥadīṯ studies. Examining the actual ḥadīṯ studies of one of the scholars at the core of al-Ḥaramayn circle, i.e. Ibrāhīm b. Ḥasan al-Kūrānī, will unpack the main interest of Ḥiǧāzī scholars in ḥadīṯ literature, reveal previously unstudied aspects of ḥadīṯ studies in the 11th/17th-century Ḥiǧāz, correct some unexamined assumptions, and situate the ḥadīṯ efforts of scholars of the 11th/17th-century Ḥiǧāz within a general framework of developments within ḥadīṯ studies.

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