The use of cellular foam as a core material in light-weight structural applications is of considerable interest. However, advances in this technology have been limited due to the lack of information concerning the macroscopic material behavior of cellular foams. Of particular interest in the design of composite structures is the shear modulus, G, of the core material, which must be established with a high degree of accuracy. Current ASTM test methods for shear modulus determination were researched and found inadequate for testing cellular foam materials. The difficulty in testing foam and the inaccuracies associated with the standard test methods established the need for the development of a test method for these materials. The test method (test fixture and test procedure) developed for cellular foam materials is presented. The design of the test fixture and the finite element analysis performed to determine fixture accuracy are discussed in detail. Additionally, the test procedure is presented, as well as the results for the 32 tests performed.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Francis Abbott Waldman. / M.S.

Thesis (M.E.)--University of Canterbury, 2007. / Typescript (photocopy). "May 2007." Includes bibliographical references (leaves 121-122). Also available via the World Wide Web.

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Thesis (MBA)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The polystyrene foam tray manufacturing industry started with a monopoly in 1954, and lasted for more than 29 years. During the last ten years the industry has grown extremely competitive, seeing many new players enter (and exit) and a reduction in industry profitability. This mini thesis attempts to analyze the polystyrene foam tray manufacturing industry in its current form and to quantify the external, new challenges it currently faces. It attempts to identify potential pitfalls for new entrants to the industry and to construct an ideal strategy suited best for the industry, based on an industry analysis. The polystyrene foam container industry background is discussed to determine its origins in South Africa. An industry and competitive analysis is done to assess the strategically relevant aspects of the industry's macro environment. A technique developed by Thompson and Strickland (1998: 68) is utilized. The scope of the macro environment in the mini-thesis was limited to the South African scenario. Ultimately, an ideal strategy, which would deal with all the relevant challenges of the industry, is proposed. The industry and competitive analysis revealed important dominant economic traits. Competition is concentrated in the country's economic hub, namely Gauteng, but regional manufacturing bases leads to extended market share in those areas. The product range spans over several hundred coloured, printed and laminated trays, but the fiercest competition across the board takes place in a few sizes white, commodity flat trays to the meat industry, which also forms the bulk of sales to the industry. The growth rate has been organic for the last few years, mainly due to the mature status of polystyrene foam tray products and the introduction of alternative (though more expensive) media. The external macro economic environment has also not been conducive to abnormally high growth (GDP in South Africa has drifted between 1% and 3% for the last few years). Five competitors exist, and two of these competitors have 80% of the market share, but are also the furthest away from the largest part of the market, namely Gauteng. Customers are divided into two groups, distributors and end users. Small competitors make extensive use of distributors (since they do not own their own distribution channels), while large competitors limit the use of distributors to limit the potential buying power of distributors. The barrier to entry for a new entrant wanting to acquire up to 5% of market share is around R 10m, which includes working capital. The industry profitability varies from losses to extreme profits in some years. This becomes a vicious circle, since the latter attracts new entrants, which in turn causes price wars. Rivalry amongst competitive sellers is excessive, specifically when new entrants appear on the scene. Price cutting, although a very blunt tool, is used almost exclusively to obtain a volume advantage. Substitute products do not really pose a threat in the South African economic situation where cost is all-important. No other packaging medium can compete with the wide range of applicability, low cost and strength of polystyrene foam. Where end-user markets are more affluent, substitute products may have a minor impact. The power of suppliers in the industry is limited, since there is a manufacturing over capacity in the country, and there are no switching costs when changing from one supplier to another. The power of buyers, specifically ones that buy in bulk (distributors and the like), is thus quite strong. The main drivers of change include excessive movement in market pricing, product innovation, technological changes, increasing globalisation of the industry and changing societal concerns. Movement in market pricing is by far the most important and has the greatest affect on industry profitability, since the complete product range is affected. The latter four drivers affect mostly branded and speciality product. Strategic group mapping, combined with an in-depth analysis of each competitor, revealed that the largest two players, Kohler Versapak and Atlantic Forming, are definitely in the strongest position from a financial point of view. Although drawbacks such a corporate red tape, shareholder pressure and geographic location exist for these competitors, sheer financial strength to survive price wars will give them an edge. With the current amount of competitors and over capacity in the market there is bound to be some consolidation in the manufacturing industry. It seems that one of the larger two players (Kohler Versapak or Atlantic Forming) may acquire one of the smaller manufacturers in a bid to stabilize market prices. The most important key success factor is the ability to produce polystyrene foam trays at the lowest possible cost. The absence of switching costs, price wars and a manufacturing over capacity are all causes of the preceding success factor. Other less important success factors are distribution related (being close to the market is an advantage) and technology related (being able to develop advanced branded and functional trays). In its current status, where there is a supply-demand imbalance, the industry does not seem attractive. Although negative external forces such as environmental pressure, are limited, growth potential is limited and competition is fierce. In summary none of the competitors have attempted to utilize other tools than pricecutting to protect market share. From a geographic location point of view, Airshield and Mainpack are positioned best, but do not possess the financial momentum to optimally utilise their location in terms of finished product distribution and raw material acquisition. Atlantic Forming and Kohler Versapak seem to have expanded their product ranges to low profit and unprofitable products, while the other competitors have stayed focused on a few high volume items. It seems that it may have been a better idea for the larger players to utilize existing resources on other profitable media rather than expanding its interests in polystyrene foam trays. / AFRIKAANSE OPSOMMING: Polistireen skuim houer vervaardiging het in 1954 met 'n monopolie begin wat vir 29 jaar staande gebly het. Gedurende die laaste tien jaar het die polistireen skuim industrie baie kompeterend geraak, met heelwat kompeterende maatskappye wat die mark betree het (en uitgetree het), en 'n gevolglike afname in industrie profyt gehad het. Hierdie minitesis poog om die polistireen skuim bakkie industrie te analiseer in sy huidige vorm en om die eksterne uitdagings wat tans bestaan, te identifiseer. Die tesis poog verder om potensiele probleme te identifiseer wat nuwe kompeterende maatskappye in die industrie mag teëkom, en dan om 'n ideale strategie saam te stel, gebasseer op 'n industrie analise. Die polistireen skuim houer industrie is bespreek, sodat die oorsprong van die industrie in Suid-Afrika bepaal kon word. 'n Industrie en kompeterende analise is gedoen om die strategies belangrike aspekte van die industrie se makro omgewing te bepaal. Vir die bogenoemde analise is 'n tegniek soos ontwikkel deur Thompson en Strickland (1998: 68) gebruik. Die omvang van die makro omgewing in hierdie minitesis is beperk tot die Suid- Afrikaanse omgewing. Die uiteindelike ideale strategie sal al die relevante uitdagings van die industrie aanspreek. Die industrie en kompeterende analise het belangrike dominante ekonomiese eienskappe blootgelê. Markgerigte kompetisie is gekonsentreerd in die land se ekonomiese enjin, naamlik Gauteng, maar streeks gebaseerde vervaardigings aanlegte lei gewoonlik tot 'n verbeterde mark aandeel in 'n spesifieke streek. Die produk reeks bestaan uit honderde gekleurde, gedrukte en gelamineerde houers, maar die grootste kompetisie vind plaas oor slegs 'n paar plat, wit vleis bakkies - wat ook die grootste volume verkope in die industrie beslaan. Die groei tempo was organies vir die laaste paar jaar, hoofsaaklik as gevolg van die volwasse stand van polistireen skuim produkte en die bekendstelling van alternatiewe produkte. Die eksterne makro ekonomiese omgewing het ook nie bygedra tot bogemiddelde groei nie (BBP in Suid-Afrika het tussen I% en 3% gewissel vir die laaste paar jaar). Vyf produseerders van polistireen skuim houers ding mee in die mark, en twee van hulle besit 80% van die totale mark aandeel, alhoewel hulle ook die verste vanaf grootste mark, naamlik Gauteng, is. Kliënte word in twee groepe verdeel, naamlik verspreiders en eind-gebruikers. Klein produseerders maak meestal gebruik van verspreiders omdat hulle nie oor hulle eie verspreidings kanale beskik nie. Groter produseerders beperk die gebruik van verspreiders om uiteindelik potensiële koopkrag van verspreiders te beperk. Vaste kapitaal, asook lopende kapitaal om ongeveer 5% van die mark te bekom, is ongeveer R10m. Die industrie profyt variëer tussen verliese tot oorgrote profyt in sommige jare. Hierdie variasie vorm 'n afbrekende sirkel, aangesien oorgrote profyt potensiële nuwe produseerders aantrek wat dan weer tot prys oorloë lei. Mededinging tussen kompeterende produseerders is oormatig sterk, spesifiek wanneer nuwe produseerders die mark betree. Alhoewel prys verlaging 'n redelike kru metode is om markaandeel te bekom, word dit amper uitsluitlik gebruik. Alternatiewe, duurder vervangings produkte is nie werklik 'n gevaar vir polistireen skuim produkte in Suid-Afrika nie, aangesien prys die belangrikste element is. Geen ander verpakkingsmedia kan meeding met die toepasbaarheid, lae koste en sterkte van polistireen skuim nie. Slegs in sekere wel-gestelde segmente van die mark kan alternatiewe produkte 'n minimale impak op die polistireen skuim mark toon. Die mag van verskaffers in die industrie is beperk, aangesien daar 'n geweldige oorkapasiteit in die land is en omdat daar geen oorskakelingskoste bestaan wanneer daar van een verskaffer tot 'n ander geskuif word nie. Die mag van kopers, en spesifiek die wat in grootmaat koop, is dus redelik sterk. Die hoofdrywers van verandering sluit in sterk beweging in mark pryse, produk innovasie, tegnologiese veranderinge, toenemende globalisering van die industrie en veranderende sosiale standaarde. Variëerende beweging van markpryse is by verre die belangrikste en het ook die grootste effek op industrie profyt, aangesien die hele produk reeks geraak word. Die laaste vier drywers affekteer meestal handelsmerk produkte en spesialiteits produkte. Strategiese groep kaarte, gekombineerd met 'n indiepte analise van elke produseerder, het aangedui dat die twee grootste kompeteerders, Kohler Versapak en Atlantic Forming, definitief in die sterkste posisie is vanaf 'n finansiële oogpunt gesien. Alhoewel negatiewe punte soos korporatiewe sloering, aandeelhouer druk en geografiese posisie teen die twee mededingers tel, sal blote finansiele mag om prys oorloë te deurstaan hulle die oorhand gee. Met die huidige hoeveelheid oorkapasiteit in die mark moet daar uiteraard konsolidasie in die vervaardigings industrie plaasvind. Dit is waarskynlik dat een van die groter spelers (Kohler Versapak of Atlantic Forming) van die kleiner mededingers mag bekom in 'n poging om die mark te stabiliseer. Die mees belangrike sleutel sukses faktor is die vermoë om polistireen skuim bakkies teen die laagste koste te vervaardig. Die afwesigheid van oorskakelingskoste, die aanwesigheid van prys oorloë en vervaardigings oorkapasiteit is almal oorsake van die genoemde sukses faktor. Ander minder belangrike sukses faktore is verspreidings verwante (om nabyaan die mark te wees is 'n voordeel) en tegnologie verwante (om handelmerk produkte en moderne funksionele produkte te kan ontwikkel) faktore. In die mark se huidige vorm is daar nie 'n vraag-aanbod balans nie, en lyk die industrie nie aantreklik nie. Alhoewel negatiewe eksterne kragte soos omgewings druk beperk is, is groei potensiaal ook beperk en kompetisie agressief. Opsommendergewys het geen van die mededingers ander metodes as prys verlaging probeer gebruik om mark aandeel te beskerm nie. Vanaf 'n geografiese oogpunt gesien, is Airshield en Mainpack die beste geposisioneer, maar hulle het nie die finansiële momentum om hulle posisie optimaal te benut in terme van klaar produk verspreiding en rou material aankope nie. Atlantic Forming en Kohler Versapak het hulle produk reeks uitgebrei na lae profit en verlies-lyende produkte, terwyl ander mededingers gefokus gebly het op 'n paar hoë volume items. Dit lyk asof dit beter sou gewees het vir die groter spelers om bestaande bronne te gebruik het op ander winsgewinde media as om verder uit te brei in polistireen skuim.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVIALABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 118-119. / by Jane Ellen Martini. / M.S.

This thesis addresses a new technique of foaming on polymer-paperboard composites which combines the advantages of traditional polymeric foam with the environmental benefits of paperboard. Paperboard is sandwiched between two extruded polymeric layers of different densities. On application of heat, one face is foamed by the evaporating moisture in the board; the other face serves as a barrier. This work is directed at gaining a better understanding of the fundamental processes in foaming polymers on paperboard. The ultimate goal is to be able to produce uniform bubbles of a predetermined size on the surface so as to give optimum heat insulation and good tactile properties. Bubble growth was studied as a function of paperboard properties, polymer melt index, extrusion speed, polymer thickness, temperature and moisture content. The foam quality (thickness) is also related to the cell size distribution and various factors affecting it are identified. A combination of experimental techniques such as high speed imaging, infrared thermography and scanning electron microscopy is used for this purpose. Foaming on paper-polymer composites is caused by water vapor escaping through the pores present in the paperboard substrate and then foaming the polymer. The vapor driving force which dominates foaming and overcomes the less significant viscoelastic and surface tension opposition forces depends on the paperboard properties as well as on the ability of the polymer to bond with the paperboard. It was found that the bubble size distribution directly relates to the pore size distribution on the paperboard. The bubble size was also controlled by the thickness of the polymer layer and its ability to bond with the paperboard. Coalescence subsequently led to thicker foams due to the formation of larger sized bubbles.

Shape memory polymer (SMP) materials have the ability to remain in a deformed state and then recover their initial/cast shape. This property has significant potential in many different fields, including aerospace and bio-medical, in which a shape change is desirable and actuation may not be required. SMP materials have been made into nano-reinforced composites and also foamed to improve desired properties for specific applications. SMP foams offer two clear advantages over non-foam SMP materials in applications for the biomedical and aerospace fields. The key advantages are lower density and significant compressibility. The significance of this is that components made out of SMP foam are lighter than traditional SMP materials, more compressible and exhibit minimal transverse change during deformation and shape recovery. This increases the performance and efficiency of devices using SMP foam material. The need for a set of design criteria, models, and limits for the use of shape memory polymer foams was proposed. The effect of temperature and strain on the mechanical behavior, compression, tensile, cyclic compression, constrained recovery and free strain recovery of the material was used to determine the operational limits of the material. Next, the damage mechanism and viscoelastic effects in compressive cycling were determined through further mechanical testing and with the incorporation of three dimensional structure mapping via micro-CT scanning. The influence of microstructure was determined by testing the basic thermomechanical, viscoelastic and shape recovery behavior of foams with relative densities of 20, 30 and 40 percent. A similar suite of tests was then performed on the base epoxy material to generate the material properties necessary to fit constitutive equations to enable computational modeling. This data was then combined with three dimensional microstructures generated from micro-CT scans to develop material models for shape memory foams. These models were then validated by comparing model results to the experimental results under similar conditions.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 152-167).