Microscopic Studies of Syntactic Foams Tested Under Three-Point Bending Conditions

2002 ◽  
Author(s):  
Nikhil Gupta ◽  
Eyassu Woldesenbet
Keyword(s):  
Moisture Absorption ◽  
Syntactic Foam ◽  
Local Stress ◽  
Core Material ◽  
Syntactic Foams ◽  
Compression Tests ◽  
Three Point Bending ◽  
Microscopic Studies ◽  
Stress States ◽  
Point Bend

Use of syntactic foam as core material in the sandwich structured composites is increasing due to its higher compressive strength, damage tolerance and low moisture absorption compared to the open cell structured foams. Extensive microscopic examination of the syntactic foams tested under compressive and three-point bending conditions is undertaken in this study. The aim of the investigation is to determine the local fracture mode and correlate it with the microscopic structure of the material. Local stress states are identified in the material based on the microscopic fracture features. Syntactic foam tested in the study has resin to microballoons ratio of 1.52 by weight. Compression tests were conducted on the syntactic foam specimens having two different aspect rations, which were 0.4 and 0.91. Three-point bend tests were conducted on the sandwich structures containing syntactic foam as core material and glass fabric as the skin material.

scholarly journals Characterisation of Aluminium Matrix Syntactic Foams under Static and Dynamic Loading

2011 ◽  
Vol 82 ◽  
pp. 142-147 ◽  
Author(s):  
Mohamed Altenaiji ◽  
Graham K. Schleyer ◽  
Yo Yang Zhao
Keyword(s):  
Compressive Strength ◽  
Porous Ceramic ◽  
Syntactic Foam ◽  
Absorption Capacity ◽  
Core Material ◽  
Aluminium Matrix ◽  
Test Machine ◽  
Syntactic Foams ◽  
Pressure Infiltration ◽  
Energy Absorbing

Development of a lightweight, strong and energy-absorbing material that has potential application for the protection of vehicles and occupants against impact and blast, is a difficult challenge facing the materials community. Aluminium matrix syntactic foams will be investigated as a possible core material as part of a multi-layered protection system for military vehicles. Aluminium matrix syntactic foams are composite materials consisting of an aluminium matrix implanted with hollow or porous ceramic particles. This paper investigates the mechanical properties of aluminium matrix syntactic foam with different sizes of ceramic micro-spheres and different grades of aluminium, fabricated by the pressure infiltration method. The static crushing behaviour of the foam was investigated under two test conditions using an Instron 4505 machine. Results are compared and discussed. The dynamic compressive response was investigated using a drop-weight impact test machine. It was found that the particle size of the ceramic micro-spheres and the grade of the aluminium metal have a significant effect on the energy absorption capacity of the material. The compressive strength of the syntactic foam was found to increase with increasing compressive strength of the metal matrix.

scholarly journals Effect of Heat Treatment on the Compressive Behavior of Zinc Alloy ZA27 Syntactic Foam

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 792 ◽  
Author(s):  
Nima Movahedi ◽  
Graeme Murch ◽  
Irina Belova ◽  
Thomas Fiedler
Keyword(s):  
Heat Treatment ◽  
Microstructural Analysis ◽  
Syntactic Foam ◽  
Metallic Matrix ◽  
Ductile Deformation ◽  
Zinc Alloy ◽  
Syntactic Foams ◽  
Compression Tests ◽  
Static Compression ◽  
Heat Treated

Zinc alloy (ZA27) syntactic foams (SF) were manufactured using expanded perlite (EP) particles and counter-gravity infiltration casting. Due to a variation of the metallic matrix content, the density of the produced foam samples varied from 1.78 to 2.03 g·cm−3. As-cast and solution heat-treated samples were tested to investigate the compressive properties of the ZA27 syntactic foam. To this end, quasi-static compression tests were conducted. In addition, microstructural analysis of the as-cast and heat-treated syntactic foams was carried out using scanning electron microscopy. The results indicate that the heat treatment alters the microstructure of the ZA27 alloy matrix from a multiphase dendrite to a spheroidized microstructure with improved ductility. Moreover, the heat treatment considerably enhances the energy absorption and plateau stress ( σ pl ) of the syntactic foam. Optical analysis of the syntactic foams under compression shows that the dominant deformation mechanism of the as-cast foams is brittle fracture. In comparison, the heat-treated samples undergo a more ductile deformation.

scholarly journals Functionally-Graded Metallic Syntactic Foams Produced via Particle Pre-Compaction

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 314 ◽  
Author(s):  
Thomas Fiedler ◽  
Nima Movahedi ◽  
Lucas York ◽  
Steffen Broxtermann
Keyword(s):  
Syntactic Foam ◽  
Functionally Graded ◽  
Syntactic Foams ◽  
Compression Tests ◽  
Graded Materials ◽  
Static Compression ◽  
X Ray Imaging ◽  
Foam Properties ◽  
A356 Aluminum ◽  
Particle Beds

This paper introduces a novel functionally graded metallic syntactic foam. The investigated foams are manufactured while using infiltration casting where molten A356 aluminum flows into the interstitial voids of packed expanded perlite (EP) particle beds. The partial pre-compaction of particle beds enables the creation of distinct and reproducible density gradients within the syntactic foam. In this study, the samples are produced using four gradually increasing compaction forces and are compared to non-compacted samples. X-ray imaging is used to detect the resulting spatial variation of foam density. In addition, quasi-static compression tests are performed to determine the mechanical foam properties. The results suggest that particle pre-compaction is an efficient tool for tailoring the density and mechanical properties of these novel functionally graded materials.

The Static Strength of Syntactic Foams

1969 ◽  
Vol 36 (3) ◽  
pp. 551-557 ◽  
Author(s):  
J. A. DeRuntz ◽  
O. Hoffman
Keyword(s):  
Principal Stress ◽  
Syntactic Foam ◽  
Failure Surface ◽  
Biaxial Stress ◽  
Resin Matrix ◽  
Experimental Program ◽  
Syntactic Foams ◽  
Stress Space ◽  
Load Paths ◽  
Stress States

A failure condition is proposed for the composite material “syntactic foam” based upon an experimental program carried out under combined biaxial and triaxial stress states. The material itself is composed of hollow glass “microspheres” embedded in an epoxy resin matrix. It exhibits finite strength under hydrostatic compression, unlike any other engineering material and thus gives rise to a closed failure surface in principal stress space. In addition to loadings corresponding to radial lines starting from the origin in stress space out to the failure envelope, other load paths were also used. Some effects due to loading and unloading and then reloading to another stress state were also investigated. Under biaxial stress states it was found that the ultimate strength of the material is sensitive to its past stress history to some degree, the reason being attributed to the initially isotropic material developing weak planes perpendicular to the compressive principal stress resulting in a “latent anisotropy.”

Syntactic foam under compressive stress: Comparison of modeling predictions and experimental measurements

2020 ◽  
pp. 0021955X2094311
Author(s):  
Baptiste Paget ◽  
Matthieu Zinet ◽  
Philippe Cassagnau
Keyword(s):  
Syntactic Foam ◽  
Model Parameters ◽  
Syntactic Foams ◽  
Compression Tests ◽  
Confined Compression ◽  
Model Predictions ◽  
Soft Shell ◽  
The Matrix ◽  
The Relationship ◽  
Critical Buckling Pressure

Syntactic foams are composite materials consisting in the association of hollow particles, called “microspheres” and a polymer matrix. The use of soft shell microspheres confers to the foam interesting properties but in return increases significantly its compressibility. Therefore, understanding and predicting the relationship between pressure and volume change is a crucial issue for the development of this type of material. The present study focuses on a high void fraction syntactic foam made with soft shell polymer microspheres embedded in a polyurethane matrix. Compression tests are performed using a capillary rheometer and a PVT accessory for the hydrostatic compression, and a more conventional apparatus for the confined compression. The experimental results are compared with De Pascalis’s pressure/volume model predictions, using Fok and Allwright’s model to determine the critical buckling pressure of the microspheres. The model proves to be fairly accurate at low pressure and high pressure, despite a notable deviation in the mid-pressure range. The influence of key model parameters such as microsphere size distribution and microsphere and matrix elastic properties is investigated. It is shown that the reinforcement of the matrix seems to be the only efficient way to limit the compressibility of such a syntactic foam.

Compressive Behaviour of Low Density Polymeric Syntactic Foams

2015 ◽  
Vol 799-800 ◽  
pp. 135-139
Author(s):  
Zulzamri Salleh ◽  
Md Mainul Islam ◽  
Jayantha Ananda Epaarachchi
Keyword(s):  
Mechanical Properties ◽  
Syntactic Foam ◽  
Syntactic Foams ◽  
Compression Tests ◽  
Weight Percentage ◽  
Polymer Resin ◽  
Compression Properties ◽  
Materials Used ◽  
Marine Applications ◽  
Good Compression

The combinations of polymer resin and glass microballoon are the main materials used to produce syntactic foams. Syntactic foam is a lightweight material that has good mechanical properties and is commonly used as a component for structural materials in civil construction, aerospace and marine applications. Hence, it should have suitable mechanical properties, particularly good compression behaviour. In the present study, the results obtained from compression tests are compressive strength, elastic modulus and specific compression that decrease when increasing of glass microballoon contents (2.0 wt.%, 4.0 wt.%, 6.0 wt.%, 8.0 wt.% and 10.0 wt.%) and also neat resin. The highest strength value for compression testing is owned by 2.0 wt.% which is 88.9 MPa, while the lowest strength is 43 MPa that belongs to 10.0 wt.% of glass microballoon. This shows that the density and weight percentage of glass microballoon in these syntactic foams affect compression properties. Therefore, a further study should be conducted, which includes the effect of compressive failure mechanism.

On the Characterisation of Syntactic Foam Core Sandwich Composites for Compressive Properties

1999 ◽  
Vol 18 (14) ◽  
pp. 1347-1357 ◽  
Author(s):  
Nikhil Gupta ◽  
S. Sankaran
Keyword(s):  
Syntactic Foam ◽  
Core Material ◽  
Central Plane ◽  
Foam Core ◽  
Syntactic Foams ◽  
The Core ◽  
Fracture Event ◽  
Glass Carbon ◽  
Sandwich Constructions ◽  
Core Materials

Sandwich structures, especially those with honeycomb and grid structures as the core material, are very commonly employed in aircraft structures. There is an increasing use of closed-pore rigid syntactic foams as core materials in sandwich constructions because they possess a number of favourable properties. The syntactic foams, owing to their structure and formation, behave differently under compression compared to other traditionally used core materials. In the present study, therefore, syntactic foam core sandwich constructions are evaluated for their behaviour under compression in both edgewise and flatwise orientations. Further, the work characterises the relative performance of two sets of sandwich materials, one containing glass-epoxy and the other, glass/carbon hybrid-epoxy skins. As non-standard geometry test specimens were involved, only a comparative evaluation was contemplated in this approach. The experiments indicate that the nature of the reinforcement fabric in the skin has a bearing on the test results in edgewise orientation. Thus, the tendency towards initiation of vertical crack in the central plane of the core material, which is a typical fracture event in this kind of material, was found to occur after a delay for the specimens containing the glass fabric in the skin. Attempts are made to establish the correlation between observations made on the test specimen visually during the course of testing and the post-compression microscopic examinations of the fracture features.

The effect of nano-additive reinforcements on thermoplastic microballoon epoxy syntactic foam mechanical properties

2017 ◽  
Vol 52 (7) ◽  
pp. 971-980 ◽  
Author(s):  
Kerrick R Dando ◽  
David R Salem
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanofiber ◽  
Volume Fraction ◽  
Syntactic Foam ◽  
Halloysite Nanotubes ◽  
Core Material ◽  
Mechanical And Thermal Properties ◽  
Syntactic Foams ◽  
Micro Computed Tomography ◽  
Halloysite Nanotube

Syntactic foams comprising glass microballoons have gained considerable attention over the past several years due to mechanical and thermal properties that are advantageous for use as a core material in naval and aerospace applications. Recent advancements in the production of thermoplastic microballoon syntactic foams have allowed for an increase in microballoon volume fraction (up to 0.9 volume fraction), with correspondingly lower densities but reduced mechanical properties. In this work, carbon nanofibers and halloysite nanotubes were incorporated in thermoplastic microballoon-based syntactic foam to enhance the mechanical properties and the relative effects of these two nanoscale reinforcements were compared. X-ray micro-computed tomography was employed to analyze the microstructure of the materials produced, and scanning electron microscopy was used to assess the dispersion of nano-additives within the resin. Compressive strength and modulus enhancements as large as 180% and 250% respectively were achieved with a 0.25 wt% addition of carbon nanofiber and increases of 165% and 244% respectively were achieved with a 0.5 wt% addition of halloysite nanotube. Tensile strength and modulus enhancements as large as 110% and 165% respectively were achieved with a 0.125 wt% addition of carbon nanofiber and increases of 133% and 173% respectively were achieved with a 0.125 wt% addition of halloysite nanotube.

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.

Effect of Phase Transformation on the Wear Behavior of NiTi Alloy

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
M. Abedini ◽  
H. M. Ghasemi ◽  
M. Nili Ahmadabadi ◽  
R. Mahmudi
Keyword(s):  
Wear Behavior ◽  
Niti Alloy ◽  
Testing Temperature ◽  
Compression Tests ◽  
Scanning Calorimetry ◽  
Three Point Bending ◽  
Mechanical And Tribological Properties ◽  
Ni Alloy ◽  
Shape Memory Effects ◽  
Pin On Disk

In this paper, mechanical and tribological properties of a Ti-50.3 at % Ni alloy were investigated. The transformation temperatures of the alloy were determined using differential scanning calorimetry. Three-point bending tests were performed to characterize the pseudoelasticity and shape memory effects. Uni-axial compression tests were also performed at different testing temperatures. The wear tests were conducted using a pin-on-disk tribometer at testing temperatures ranging from 0°C to 80°C. The wear results showed that with increasing the testing temperature from 0°C to 50°C, the wear of the alloy was decreased, which could be attributed to the higher pseudoelasticity of the alloy at a testing temperature of 50°C. The pseudoelasticity of the alloy decreased at a higher testing temperature of 80°C; however, its wear resistance increased considerably due to higher ultimate strength and work hardening.

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