Editing Syntactic foam

{{short description|Composite material filled with low-density spheres}}

{{use dmy dates|date=May 2018}}

{{redirect-synonym|composite foam|[[foamcore]]<!--foam concrete-->}}

[[file:syntacticfoam.JPG|upright=1.3|thumb|Syntactic foam, shown by [[scanning electron microscope|scanning electron microscopy]], consisting of [[glass microsphere]]s within a matrix of [[epoxy]] resin.]]

'''Syntactic foams''' are [[composite material]]s synthesized by filling a [[metal]], [[polymer]],<ref>{{cite journal|last=Shutov|first=F.A.|title=Syntactic polymer foams|journal=Advances in Polymer Science|year=1986|volume=73-74|pages=63–123|doi=10.1007/3-540-15786-7_7|isbn=978-3-540-15786-1}}</ref> [[cement]]itious or [[ceramic]] matrix with
spheres as [[Aggregate (composite)|aggregates]].<ref name="lm2">{{Cite web|url=http://www.crgrp.com/technology/portfolio/syntactics.html|title=What is Syntactic Foam?|access-date=2009-08-07|publisher=Cornerstone Research Group|url-status=dead|archive-url=https://web.archive.org/web/20120720033636/http://www.crgrp.com/technology/portfolio/syntactics.html|archive-date=20 July 2012|df=dmy-all}}</ref> The spheres may be hollow, called [[microballoon]]s<ref>{{cite journal |first1=Ho Sung |last1=Kim |first2=Pakorn |last2=Plubrai |title=Manufacturing and failure mechanisms of syntactic foam under compression |journal=Composites Part A: Applied Science and Manufacturing |volume=35 |issue=9 |date=September 2004 |pages=1009–1015 |doi=10.1016/j.compositesa.2004.03.013}}</ref> or [[cenosphere]]s, or non-hollow, for example [[perlite]].<ref>{{cite journal |first1=Dipendra |last1=Shastri |first2=Ho Sung |last2=Kim |title=A new consolidation process for expanded perlite particles |journal=Construction and Building Materials |volume=60 |date=16 June 2014 |pages=1–7 |doi=10.1016/j.conbuildmat.2014.02.041|hdl=1959.13/1052767 |hdl-access=free }}</ref> In this context, "syntactic" means "put together."<ref name="Merriam-Webster">{{cite Merriam-Webster|syntactic foam|accessdate=2023-06-22}}</ref> The presence of hollow particles results in lower [[density]], higher [[specific strength]] (strength divided by density), lower [[coefficient of thermal expansion]], and, in some cases, [[radar]] or [[sonar]] [[stealth technology|transparency]].

== History ==

The term was originally coined by the [[Bakelite|Bakelite Company]], in 1955, for their lightweight composites made of hollow [[phenol formaldehyde resin|phenolic]] microspheres bonded to a matrix of phenolic, [[epoxy]], or [[polyester]].<ref>From the Oxford English Dictionary citation of Sci. News Let. 2 Apr. 213/3</ref><ref name="JSTOR1955">{{cite journal | title = Plastic Foam Developed for Boats and Planes | journal = The Science News-Letter | date = 2 April 1955 | volume = 67 | issue = 14 | page = 213 | issn = 0096-4018 | doi = 10.2307/3935329 | jstor = 3935329 | pmid = | url = https://www.jstor.org/stable/3935331| url-access = subscription }}</ref>

These materials were developed in early 1960s as improved [[buoyant|buoyancy]] materials for marine applications.<ref name=lm3>{{Cite journal|url=http://www.nistep.go.jp/achiev/ftx/eng/stfc/stt026e/qr26pdf/STTqr2607.pdf |title=Overseas Trends in the Development of Human Occupied Deep Submersibles and a Proposal for Japan's Way to Take |access-date=2009-08-10 |journal=Science and Technology Trends Quarterly Review |volume=26 |date=January 2008 |first=Kimiaki |last=Kudo |pages=104–123 |url-status=dead |archive-url=https://web.archive.org/web/20110721125903/http://www.nistep.go.jp/achiev/ftx/eng/stfc/stt026e/qr26pdf/STTqr2607.pdf |archive-date=2011-07-21 }}</ref> Other characteristics led these materials to [[aerospace]] and ground transportation vehicle applications.<ref name="lm1">{{dead link|date=July 2015}}{{Cite web|url=http://www.sampe.org/store/paper.aspx?pid=943 |title=Novel Processing of High-Performance Structural Syntactic Foams |access-date=2009-08-07 |publisher=Society for the Advancement of Material and Process Engineering |year=2002 |first=G |last=Karst |url-status=dead |archive-url=https://web.archive.org/web/20110723181158/http://www.sampe.org/store/paper.aspx?pid=943 |archive-date=2011-07-23 }}</ref>

Research on syntactic foams has recently been advanced by [[Nikhil Gupta]].

==Characteristics==
Tailorability is one of the biggest advantages of these materials.<ref>{{cite journal|last=Bardella|first=L.|author2=Genna F. |title=On the elastic behavior of syntactic foams|journal=International Journal of Solids and Structures|year=2001|volume=38|issue=2|pages=7235–7260|doi=10.1016/S0020-7683(00)00228-6}}</ref> The matrix material can be selected from almost any metal, polymer, or ceramic. Microballoons are available in a variety of sizes and materials, including [[glass microsphere]]s, [[cenosphere]]s, [[carbon]], and polymers. The most widely used and studied [[foam]]s are glass microspheres (in epoxy or polymers), and cenospheres or ceramics<ref>{{cite journal|last=Shubmugasamy|first=V.|title=Compressive Characterization of Single Porous SiC Hollow Particles|journal=JOM|year=2014|volume=66|issue=6|pages=892–897|doi=10.1007/s11837-014-0954-7|bibcode=2014JOM....66f.892S|s2cid=40553878}}</ref> (in aluminium). One can change the volume fraction of microballoons or use microballoons of different effective density, the latter depending on the average ratio between the inner and outer radii of the microballoons.

A manufacturing method for low density syntactic foams is based on the principle of buoyancy.<ref>{{cite journal |first1=Md Mainul |last1=Islam |first2=Ho Sung |last2= Kim |title=Manufacture of syntactic foams: pre-mold processing |journal=Materials and Manufacturing Processes |volume=22 |pages=28–36 |date=2007 |doi=10.1080/10426910601015857 |s2cid=136610096 |url=https://research.usq.edu.au/download/b194f80efe12906b67f2ea94130e29f635cffffe3a4088825651d266fba4de60/8262727/Islam_Kim_MMP_v22n1_Author_Post-print.pdf}}</ref><ref>{{cite journal |first1=Md Mainul |last1=Islam |first2=Ho Sung |last2=Kim |title=Manufacture of syntactic foams using starch as binder: post-mold processing |journal=Materials and Manufacturing Processes |volume=23 |issue=8 |pages=884–892 |date=October 2008 |doi=10.1080/10426910802413661|s2cid=138333688 |url=http://eprints.usq.edu.au/4592/2/Islam_Kim_MMP_v23n8_Author_version.pdf }}</ref>

===Strength===
The [[compression (physics)|compressive]] properties of syntactic foams, in most cases, strongly depend on the properties of the filler particle material. In general, the [[compressive strength]] of the material is proportional to its density. Cementitious syntactic foams are reported to achieve compressive strength values greater than {{cvt|30|MPa|ksi}} while maintaining densities lower than {{cvt|1.2|g/cm3|oz/in3}}.<ref>{{cite journal |doi=10.1016/S0263-8223(03)00060-6 |title=Hygrothermal studies on syntactic foams and compressive strength determination |author1=Gupta, Nikhil |author2=Woldesenbet, Eyassu |date=September 2003 |volume=61 |issue=4 |pages=311–320 |journal=Composite Structures}}<!--URL: https://d1wqtxts1xzle7.cloudfront.net/75413366/s0263-8223_2803_2900060-620211130-29259-15hzmp6-libre.pdf--></ref>

The matrix material has more influence on the [[tension (physics)|tensile]] properties. [[Tensile strength]] may be highly improved by a chemical surface treatment of the particles, such as [[silanization]], which allows the formation of strong bonds between glass particles and epoxy matrix. Addition of fibrous materials can also increase the tensile strength.{{Citation needed|date=August 2012}}

==Applications==
[[File:Syntactic foam sphere.jpg|thumb|Syntactic foam sphere used as a subsurface float in [[Mooring (oceanography)|oceanographic mooring]].]]
Current applications for syntactic foam include buoyancy modules for [[marine riser tensioner]]s, [[remotely operated underwater vehicle]]s (ROVs), [[autonomous underwater vehicle]]s (AUVs), deep-sea exploration, [[hull (watercraft)|boat hulls]], and [[helicopter]] and [[airplane]] components.

''[[Cement]]itious'' syntactic foams have also been investigated as a potential lightweight structural composite material. These materials include glass microspheres dispersed in a ''cement'' paste matrix to achieve a closed cell foam structure, instead of a metallic or a polymeric matrix. Cementitious syntactic foams have also been tested for their mechanical performance under high strain rate loading conditions to evaluate their energy dissipation capacity in crash cushions, blast walls, etc. Under these loading conditions, the glass microspheres of the cementitious syntactic foams did not show progressive crushing. Ultimately, unlike the polymeric and metallic syntactic foams, they did not emerge as suitable materials for energy dissipation applications.<ref>{{Cite journal|date=2019-01-01|title=Strain rate-dependent compressive behavior and failure mechanism of cementitious syntactic foams|url=https://www.sciencedirect.com/science/article/abs/pii/S0958946518302713|journal=Cement and Concrete Composites|language=en|volume=95|pages=70–80|doi=10.1016/j.cemconcomp.2018.10.009|issn=0958-9465|last1=Bas|first1=Halim Kerim|last2=Jin|first2=Weihua|last3=Gupta|first3=Nikhil|last4=Luong|first4=Dung D.|s2cid=139598037|url-access=subscription}}</ref> Structural applications of syntactic foams include use as the intermediate layer (that is, the core) of [[sandwich panel]]s.

Though the cementitious syntactic foams demonstrate superior specific strength values in comparison to most conventional cementitious materials, it is challenging to manufacture them. Generally, the hollow inclusions tend to buoy and segregate in the low shear strength and high-density fresh cement paste. Therefore, maintaining a uniform microstructure across the material must be achieved through a strict control of the composite [[rheology]].<ref>{{Cite journal|date=2018-07-01|title=In-situ micro-CT characterization of mechanical properties and failure mechanism of cementitious syntactic foams|url=https://www.sciencedirect.com/science/article/abs/pii/S0958946517303323|journal=Cement and Concrete Composites|language=en|volume=90|pages=50–60|doi=10.1016/j.cemconcomp.2018.03.007|issn=0958-9465|last1=Bas|first1=Halim Kerim|last2=Jin|first2=Weihua|last3=Gupta|first3=Nikhil|last4=Behera|first4=Rakesh Kumar|s2cid=140068274|url-access=subscription}}</ref> In addition, certain glass types of microspheres may lead to an [[Alkali–silica reaction|alkali silica reaction]]. Therefore, the adverse effects of this reaction must be considered and addressed to ensure the long-term durability of these composites.<ref>{{Cite journal|date=2021-04-01|title=Chemical stability of hollow glass microspheres in cementitious syntactic foams|url=https://www.sciencedirect.com/science/article/abs/pii/S0958946520304327|journal=Cement and Concrete Composites|language=en|volume=118|pages=103928|doi=10.1016/j.cemconcomp.2020.103928|issn=0958-9465|last1=Bas|first1=Halim Kerim|last2=Jin|first2=Weihua|last3=Gupta|first3=Nikhil|s2cid=234059434|url-access=subscription}}</ref>

Other applications include;
*Deep-sea buoyancy foams. A method of creating submarine hulls by [[3D printing]] was developed in 2018.<ref>{{Cite web|url=https://engineering.nyu.edu/news/3-d-printing-breakthrough-lightweight-syntactic-foams-could-help-submarines-dive-deeper|title=3-D Printing Breakthrough for Lightweight Syntactic Foams Could Help Submarines Dive Deeper {{!}} NYU Tandon School of Engineering|website=engineering.nyu.edu |date=February 6, 2018 |language=en|access-date=2018-09-22}}</ref>
*Thermoforming plug assist
*Radar transparent materials
*Acoustically attenuating materials
*Cores for [[sandwich composite]]s<ref>{{cite journal |first1=Md Mainul |last1=Islam |first2=Ho Sung |last2=Kim |title=Sandwich composites made of syntactic foam core and paper skin: manufacturing and mechanical behavior |journal=Journal of Sandwich Structures and Materials |date=2012 |volume=14 |issue=1 |pages=111–127 |doi=10.1177/1099636211413564|s2cid=135970284 }}</ref><ref>{{cite journal |first1=Md |last1=Arifuzzaman |first2=Ho Sung |last2=Kim |title=Novel flexural behaviour of sandwich structures made of perlite foam/sodium silicate core and paper skin |journal=Construction and Building Materials |volume=148 |date=1 September 2017 |pages=321–333 |doi=10.1016/j.conbuildmat.2017.05.073}}</ref>
*Blast mitigating materials
*Sporting goods such as bowling balls, tennis rackets, and [[soccer ball]]s.<ref name=lm6>{{dead link|date=July 2015}}{{Cite web|url=http://www.cefic.be/templates/shwNewsFull.asp?NSID=543&HID=2&P=7|title=Performing Plastics - How plastics set out to conquer the world of sports|access-date=2009-08-10|publisher=European Chemical Industry Council|date=3 February 2005|first=Johann|last=Thim}}{{Dead link|date=June 2018 |bot=InternetArchiveBot |fix-attempted=no }}</ref>

==References==
{{Reflist}}

==External links==
*{{Commons category-inline}}

{{DEFAULTSORT:Syntactic Foam}}
[[Category:Composite materials]]
[[Category:Foams]]
[[Category:Materials science]]