Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model

2000 ◽  
Author(s):  
Zdeněk P. Bažant ◽  
Michele Brocca
Keyword(s):  
First Principles ◽  
Constitutive Law ◽  
Geometrically Nonlinear ◽  
Element Analysis ◽  
Microplane Model ◽  
Bending Tests ◽  
Three Point Bending ◽  
Closed Cell ◽  
Physical Phenomena ◽  
Good Agreement

Abstract The paper presents a new constitutive model for closed-cell polymeric foams. The model is of the microplane type. In this model, the constitutive law is characterized in terms of vectors rather then tensors. The conceptual simplicity of this ‘first-principles’ approach makes it possible to base the model more directly on the physical phenomena occurring in the microstructure, in this case the elastic bending of the cells idealized as spheres in contact. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. The softening and size effect engendered by the reduction of tangential bending stiffness due to the geometrically nonlinear effect of core indentation is discussed.

Microstructure and Strength of Low Temperature Co-Fired Ceramic Substrates With Channels and Cavities

2008 ◽  
Author(s):  
Yang-Fei Zhang ◽  
Min Miao ◽  
Yu-Feng Jin ◽  
Shu-Lin Bai
Keyword(s):  
Flexural Strength ◽  
Theoretical Calculations ◽  
Aluminum Silicate ◽  
X Ray Diffraction ◽  
Element Analysis ◽  
Ceramic Substrates ◽  
Bending Tests ◽  
Three Point Bending ◽  
Internal Structures ◽  
Fea Simulation

The effect of embedded channels and cavities on the strength of LTCC substrates has been investigated by experiments, theoretical analysis and finite element analysis (FEA) simulation. The fracture behaviors characterized by flexural strength were measured by three-point bending tests and discussed according to the features of the microstructure, which was studied by Scanning Electron Microscope, Energy Spectrum Analysis and X-Ray Diffraction methods. The experimental results show that X and Y-axial channels have little effect on the flexural strength while Z-axial via-hole will greatly lower the strength due to the stress concentration. Two distinct components were observed: particles composed of synthetic corundum and matrix composed of corundum, silica, aluminum, and sodium calcium aluminum silicate. The FEA simulation gave similar results to the experiments and theoretical calculations and proved to be an effective method to predict possible condition of the fracture on substrates with complex internal structures.

scholarly journals Switchable stiffness morphing aerostructures based on granular jamming

2019 ◽  
Vol 30 (17) ◽  
pp. 2581-2594 ◽  
Author(s):  
J David Brigido-González ◽  
Steve G Burrow ◽  
Benjamin KS Woods
Keyword(s):  
Flexural Rigidity ◽  
Fish Bone ◽  
Nonlinear Material ◽  
Element Analysis ◽  
Bending Tests ◽  
Four Point Bending ◽  
External Loads ◽  
Structural Solutions ◽  
Different Levels ◽  
Good Agreement

One of the persistent challenges facing the development of morphing aerostructures is the need to have material and structural solutions which provide a compromise between the competing design drivers of low actuation energy and high stiffness under external loads. This work proposes a solution to this challenge in the form of a novel switchable stiffness structural concept based on the principle of granular jamming. In this article, the concept of using granular jamming for controlling stiffness is first introduced. Four-point bending tests are used to obtain the flexural rigidity and bending stiffness of three different granular materials under different levels of applied vacuum loading. Nonlinear finite element analysis simulations using experimentally derived nonlinear material properties show good agreement with experiment. A specific application of this concept is then proposed based on the Fish Bone Active Camber morphing airfoil. A unit cell of this concept is built, tested and analysed, followed by the first prototype of a complete switchable stiffness Fish Bone Active Camber morphing airfoil, which is experimentally shown to be able to achieve an increase in stiffness of up to 300% due to granular jamming.

Experimental and numerical investigation on bending and compressive behavior of carbon-epoxy sandwich panel with novel M-shaped core

2022 ◽  
pp. 089270572110466
Author(s):  
Himan Khaledi ◽  
Yasser Rostamiyan
Keyword(s):  
Polyurethane Foam ◽  
Sandwich Panel ◽  
Sandwich Panels ◽  
Bending Tests ◽  
Three Point Bending ◽  
Composite Sandwich ◽  
Compressive Loads ◽  
Lattice Core ◽  
Force Displacement ◽  
Good Agreement

Present paper has experimentally and numerically investigated the mechanical behavior of composite sandwich panel with novel M-shaped lattice core subjected to three-point bending and compressive loads. For this purpose, a composite sandwich panel with M-shaped core made of carbon fiber has been fabricated in this experiment. In order to fabricate the sandwich panels, the vacuum assisted resin transfer molding (VARTM) has been used to achieve a laminate without any fault. Afterward, polyurethane foam with density of 80 kg/m3 has been injected into the core of the sandwich panel. Then, a unique design was presented to sandwich panel cores. The study of force-displacement curves obtained from sandwich panel compression and three-point bending tests, showed that an optimum mechanical strength with a considerable lightweight. It should be noted that the experimental data was compared to numerical simulation in ABAQUS software. According to the results, polyurethane foam has improved the flexural strength of sandwich panels by 14% while this improvement for compressive strength is equal to 23%. As well as, it turned out that numerical results are in good agreement with experimental ones and make it possible to use simulation instead of time-consuming experimental procedures for design and analysis.

Study on Automobile Body Performance of Honeycomb Sandwich Composite Material

2012 ◽  
Vol 567 ◽  
pp. 146-149 ◽  
Author(s):  
Xue Mei Fan ◽  
Jian Feng Wang ◽  
Cheng Jin Duan ◽  
Xiang Xin Xia ◽  
Zhao Hui Wang
Keyword(s):  
Mechanical Properties ◽  
Sandwich Structure ◽  
Testing Machine ◽  
Sandwich Composite ◽  
Element Analysis ◽  
Bending Tests ◽  
Three Point Bending ◽  
Honeycomb Sandwich ◽  
Core Thickness ◽  
Honeycomb Sandwich Structure

In order to analyze the mechanical properties of Carbon/epoxy facings-Aluminum honeycomb sandwich structure, we simulated panels of different layers and core thickness using ABAQUS finite element analysis program. And three-point bending tests and shear tests were made on the same panels using electronic universal testing machine. In addition, we also made the same three-point bending tests on steel tubes to get a comparison with honeycomb sandwich panels. It could be seen that, the simulated results were basically identified with experimental results. The results indicated that core thickness played an important role in the panels’ bulking modulus, and number of carbon fiber layers decided the shear strength. As a whole, honeycomb sandwich structure was suitable for use in the car body with good mechanical properties under premise of lighter.

Correlation of Tensile and Bending Strength of Composites With a Circular Hole

1996 ◽  
Vol 118 (4) ◽  
pp. 542-547
Author(s):  
Yi Zhao ◽  
Su-Seng Pang ◽  
Chihdar Yang
Keyword(s):  
Circular Hole ◽  
Bending Strength ◽  
Elliptic Hole ◽  
Complex Nature ◽  
Orthotropic Plates ◽  
Element Analysis ◽  
Bending Tests ◽  
Four Point Bending ◽  
Circular Holes ◽  
Good Agreement

While significant studies have been conducted on composites containing a circular or an elliptic hole under tensile loading, few investigations have been reported on notched composites under bending due to the complex nature of the problem. In this paper, a correlation of strengths of orthotropic plates containing a circular hole under tension and bending has been proposed based on Lekhnitskii’s solutions for infinite width plates. Finite element analysis has been performed to verify the theoretical correlation. Uniaxial tension and four-point bending tests have also been conducted on Scotchply samples with circular holes of various sizes. A good agreement has been observed among the theoretical, FEA, and experimental results.

scholarly journals Flexural Performance Evaluation of Novel Wide Long-Span Composite Beams Used to Construct Lower Parking Structures

2019 ◽  
Vol 12 (1) ◽  
pp. 98
Author(s):  
Yun-Chul Choi ◽  
Doo-Sung Choi ◽  
Keum-Sung Park ◽  
Kang-Seok Lee
Keyword(s):  
Flexural Strength ◽  
Composite Beams ◽  
Steel Beams ◽  
Test Results ◽  
Element Analysis ◽  
Bending Tests ◽  
Flexural Performance ◽  
Long Span ◽  
Global And Local ◽  
Good Agreement

Efficient parking structures are urgently required in Korea. The design of parking structures more than 8 m in height is difficult because both fire and seismic resistance must be considered. Existing designs are uneconomical and conservative. However, the design of parking structures less than 8 m in height is relatively simple and there are few restrictions to the construction. It is essential to optimize the design of parking structures less than 8 m in height. Here, we describe novel wide long-span composite beams that reduce the story height of low parking structures. The flexural capacity of seven of the beams was evaluated; all beams were loaded at two points prior to monotonic bending tests. We also performed finite element analysis (FEA) based on the material properties of the test specimens, and compared the results to those of the structural tests. The flexural strength of the wide composite steel beams increased by approximately 20% as the steel thickness rose by 3 mm, from 6 to 9 mm. The rebar shape (triangular or rectangular) did not affect flexural strength. The flexural strength of beams without rebar was 10% less than that of beams with rebar. The FEA and test results were in good agreement. The section plastic moments were free from global and local instability.

Stresses around large circular holes in uniform circular cylindrical shells

1982 ◽  
Vol 17 (1) ◽  
pp. 9-12 ◽  
Author(s):  
J W Bull
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cylindrical Shell ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
Element Analysis ◽  
Three Point Bending ◽  
Circular Holes ◽  
Circular Cylindrical Shells ◽  
Good Agreement

An experimental and finite element analysis of a uniform cylindrical shell with a large circular cut-out is presented. In this analysis three hole sizes are considered, namely μ = 2.037, 4.084, and 6.344 (where μ = {[12(1 - y2)]1/4/2} × [ a/( Rt)1/2]), for loadings of axial compression, torsion and three point bending. The experimental results are the only ones available for cylindrical shells with large values of μ (except for one graph by Savin (1)†), while for three point bending there is no previously published theoretical or analytical results. Good agreement is found between the calculated and experimental stresses around the holes.

Anisotropy of Bending Properties in Industrial Heat-Treatable Extruded Aluminium Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 487-492 ◽  
Author(s):  
Knuter E. Snilsberg ◽  
Ida Westermann ◽  
Bjørn Holmedal ◽  
Odd Sture Hopperstad ◽  
Y. Langsrud ◽  
...  
Keyword(s):  
Aluminium Alloys ◽  
Tensile Testing ◽  
Fracture Strain ◽  
Extrusion Direction ◽  
Grain Structure ◽  
Bending Properties ◽  
Bending Tests ◽  
Three Point Bending ◽  
Texture Characterization ◽  
Good Agreement

In the present work, three-point bending tests have been performed on four commercially extruded 6xxx- and 7xxx alloys, one with a fibrous and one with a recrystallized grain-structure for each alloy class, with the bending axis orientated 0, 45 and 90° with respect to the extrusion direction. Microstructure and texture characterization as well as tensile testing of the same materials have been performed and correlated with the bending results. In general there is good agreement between the bending angle and the fracture strain for all alloys, with the highest values in the extrusion direction. However, there are no indications in the microstructure and texture that explain the large differences in bendability observed. Die lines and recrystallized layer on a fibrous alloy have been removed to investigate their effect on the bending behaviour. However, these effects also seem to be limited, and cannot explain the anisotropy effects observed in bending angles.

Bending Properties and Finite Element Modeling of Biaxial Weft Knitted Composites

2012 ◽  
Author(s):  
O. Demircan ◽  
Y. Hamada ◽  
T. Kosui ◽  
A. Nakai ◽  
H. Hamada
Keyword(s):  
Finite Element ◽  
Composite Structures ◽  
Knitted Fabric ◽  
Bending Properties ◽  
Element Analysis ◽  
Bending Tests ◽  
Bending Property ◽  
Weft Knitted Fabric ◽  
Complex Construction ◽  
Good Agreement

In order to improve the mechanical properties of weft knitted fabric, straight yarns both in weft and warp directions can be integrated. These types of reinforcements are called biaxial weft knitted structures. Finite element analysis is a well known method for analysis of complex construction with complex material properties. Therefore, we wanted to use FEM to express the possibility of prediction of bending properties of complex biaxial weft knitted (BWK) composite structures. The purpose of this study is to investigate bending properties of BWK composites by experimentally and numerically. Two types of six plies composite panels, which include fiber contents, such as glass-glass-aramid and aramid-aramid-aramid, were fabricated by hand lay-up method. After production of composites, bending tests had been conducted on specimens. Glass-glass-aramid composites exhibited superior bending property than aramid-aramid-aramid specimens. The good agreement between the experimental results and numerical results validated the applicability of finite-element method for biaxial weft knitted composites.

Room Temperature Brittlement of T2 in the Mo-Si-B System

2013 ◽  
Vol 747-748 ◽  
pp. 132-138
Author(s):  
Kun Ming Pan ◽  
Lai Qi Zhang ◽  
Wei Du ◽  
Jun Pin Lin
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
Cleavage Crack ◽  
Single Edge ◽  
Covalent Bonds ◽  
Bending Tests ◽  
Three Point Bending ◽  
Plasma Sintering ◽  
Edge Notch ◽  
Single Edge Notch Bend

Compression and three-point bending tests were conducted at room temperature (RM) on the Mo5SiB2 (T2) alloy, which was prepared by sparking plasma sintering (SPS). It was found that almost no plastic deformation occured in the T2 alloy before failure but with a tremendous compressive strength of 2907 MPa. The fracture toughness determined from the single edge notch bend specimen is 3.34 MPa·m1/2, similar to the value of 3.5 MPa·m1/2 in ɑ-Al2O3. Once the cleavage crack initiated near the notch under continuous loads, it propagated on a certain plane (001) until the specimen completely fractured. In this work, the electronic structure was also calculated by the first-principles method, indicating that the contribution to RM brittleness is mainly caused by the covalent bonds which arrange alternately in the T2 phase.

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