A. Bledzki

Transversal strength tests and impact bending tests are performed on two glass fibre reinforced Epoxy systems and four different glass fibre sizings: PE, Silane, PU, and Epoxy. The influence of the very different fibre/matrix interfaces on the transversal strength is determined fast and with high significance. Although the transversal strength is best with Epoxy sizing, the damage tolerance is reduced. An intermediate interface strength is suggested for a well-ballanced behavior of GFRP.

ABSTRACT compounds of iron. By means of a skillful regulation of these processes it is possible to achieve a sufficient increase in the strength of adhesive boundary layers and, at the same time, an increase in interfacial bonding. From a comparatively wide selection of methods for regulation of Contact oxidation reactions in the presence of reactive polyfunctional compounds: isocyanates, silane derivatives, etc. [1] (which form links with oxygen-connecting groups of oxidized polymer and with active centers of the metal surface) are particularly signifcant to note. Nevertheless, our experience shows that the durability (including water-resistance) of adhesive joints achieved in this way is not quite sufficient. High water-resistance of adhesive joints of metals and curable epoxides is well-known. It has been proved [3] that two-link adhesives (TLA) in which curable epoxides act as components and provide a direct durable adhesive bond with steel could be very promising. The second component of TLA must serve as an intermediate agent which links together epoxide and polyolefine components. The purpose of this work is to find out further possibilities for making use of TLA to bind polyethylene with steel. Materials. The basic thermoplastic polyolefins used in the study were low-density polyethylene (PE) in a powder (average particle size is 0.150 ram) and pellet form (SU Standard 15803-02), as well as ethylenevinylacetate copolymer (EVAC) with a certain vinylacetate unit content, 12 % (SU Standard 11306-075) (see Table 1). Epoxides, bisphenol A - epichlohydrin condensates, with a content of epoxy groups 22 and 8 % respectively, were used. The latter (hard epoxide, HE) was prepared by polycondensation of the former (E) with resorcinol in the presence of triethanolamine. Hexamethilendiamine (HMD) as curing agent of E was used. Additives used were: polysocianate (PIC), a mixture of diphenylmethandiisocianate and polysocianates, with polymerization degree from 2 to 5 (SU standard, D grade), chlorsulphonated polyethylene (HSPE) (content of C1 - 27%, S - 2.4%) and melamine (MA) (as a cross-linking agent for HSPE). A cold-rolled steel (SU standard, grade 08kp) foil thickness - 0.20 mm, surface roughness profilometry 1.8 ffm) as metal substrate was used. Adhesives. For laminated TLA liquid E containing 12.0 mass % of HMD was used. Dispersed TLA were prepared m two stages. First, a PE powder was mixed with a proper amount of 10% PIC solution in acetone (manually, 20 rain) and subsequently dried at room temperature. A modified PE powder was mixed then with a proper amount of powdered HE (average size of particles was 0.150 ram), To prepare ultradispersed TLA, necessary additives were mixed into a melted basic polyolefine (PE, EVAC) on microrolls with subsequent compression moulding of sheets between cellulose triacetate films at 130~ (thickness - 1.0 mm). Tensile characteristics of adhesives were obtained using double-spade test specimens (length of main part - 10 ram, width - 5 mm, thickness - 1.0 ram) at room temperature; deformation rate 50 mm/min (average value of 12 measurements). Values of glass-transition temperature for cured E were obtained using Mettler DSC at a heating rate 10~ Surface Treatment of Metal Substrate. Traditional electrochemical etching (sulfuric acid aqueous solution 200 g/liter; current density 1.0 A/dm2; 1.5 min at 70~ with subsequent passivation (aqueous solution of CrO 3, 1%; at 1 min at 55~ Finalizing activities were a careful rinsing with distilled hot water (80~ 1 b/dm z) and drying in warm air stream (60~ Adhesive joints (AJ) (metal-polymer and polymer metal; see also Fig. 3) were made by compression at 0.4 MPa, fixed temperature and time. Peel strength testing was carried out for strips of AJ (length and width are 10 ram) at a deformation rate 50 mm/min and peel angle - 180 ~ (average value of 6-7 measurements).

ABSTRACT In real composite materials an additional phase may exist between the fiber and the matrix. This phase, commonly known as the interphase, is a local region that results from the matrix bonds with the fiber surface or the fiber sizing. The differing thermal expansions or contractions of the fiber and matrix cause thermally induced stresses in composite materials. In the present study, a four-cylinder model is proposed for the determination of residual thermal stresses in unidirectional composite materials. The elastic modulus of the interphase is a function of the interphase radius and thickness. The governing equations in terms of displacements are solved in the form of expansion into a series [1]. The effective elastic characteristics are obtained using the finite element approach. The effect of the interphase thickness and different distributions of the interphase Young's modulus on the thermal residual stress field in unidirectional composite materials is investigated.

Identification of elastic properties of unidirectional glass/epoxy laminates from the measured eigenfrequencies has been performed. The stiffness of the laminates has been investigated by a mixed numerical/experimental method employing the vibration test of plates. Elastic constants of laminates have been determined by using an identification procedure based on experiment design, the finite-element method and the response-surface approach. Elastic properties of

ABSTRACT: This article presents the investigations on the cell morphology, surface roughness, impact properties, and odor concentration of microcellular wood fiber reinforced PP composites in injection molding process with different chemical foaming agents. The ...

Polycarbonate microfoams produced by physical blowing agents usually have an unacceptable surface quality. The surface is rough and the visual difference in the surface quality is striking. However, the surface quality can be improved by the gas counterpressure technology.Polycarbonate has a high elongation at break but a low notched impact strength. Earlier, the microfoams showed higher notched impact strength, but a considerably reduced elongation at break. Foams produced by the gas counter-pressure technology have both these positive mechanical properties.

The interlaminar fracture behavior of unidirectional glass fiber reinforced composites with fiber surface treatment has been investigated in modes I and II and for fixed mode I to mode II ratio of 1.33. The data obtained from these tests have been analyzed by using different analytical approaches. The present investigation is focused on the influence of the glass fiber surface

ABSTRACT The influence of mixing process (in a two-roll mill, high-speed mixer, or twin-screw extruder) on the strength properties of polypropylene/wood fiber composites was studied. The best results were obtained for composites compounded in a twin-screw extruder. The water uptake and the influence of moisture on the flexural strength (σfl) and modulus (Efl) were studied by immersion of the composites in water at 20, 50, and 90°C. Most strongly the moisture affected the value of Efl, but the degree of water uptake and the change in σfl and Efl also depended on temperature and the presence of a modificator—maleated polypropylene (MAH). MAH improved the strength properties of the composites both in dry and wet states and also decreased the extent of water uptake and swelling in cyclic (soaking/drying) tests.

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ABSTRACT The correlation between mechanical and Theological properties of low-density polyethylene (LDPE) waste and LDPE/HDPE (high-density polyethylene) waste blends with different degrees of degradation has been investigated. To predict the suitability of PE wastes for a blown-film extrusion process, parameters such as melt flow index, morphology of the extrudate's surface, and melt elongation at break were determined. For the binary blends of LDPE/HDPE waste, the melt flow index ratio of the components was also used. Blown-film extrusion of this PE waste is possible only within the defined critical values of these parameters.

... The thickness of the specimen was 2h = 3 mm with the symmetric split. Precracks of length from 4 mm to 10 mm by loading with the crack opening mode were introduced before testq , so that the initial position of the crack tip was at the middle of the half span of the beam. ...

ABSTRACT Die kritische Einstellung der deutschen Öffentlichkeit zu Umweltfragen hat auch die Welt der Gerüche erfasst.In den letzten Jahren haben die Bewertung und Verminderung von Gerüchen bei der Anwendung von Kunststoffen zunehmend an Bedeutung gewonnen. War es zunächst die Verpackungsbranche, die Produkte für Lebensmittelverpackungen olfaktometrisch untersuchte, so zeigt in den letzten Jahren die Automobilindustrie zunehmendes Interesse für Geruchsbestimmung und Messung, nicht zuletzt wegen des zunehmenden Einsatzes von naturfaserverstärkten Werkstoffen im Fahrzeuginnenraum.Naturfaserverstärkte Kunststoffe haben neben Vorteilen gegenüber glas- und kohlefaserverstärkten Systemen (mechanisches Verhalten/Gewicht, ausgeglichene CO2-Bilanz) auch Eigenschaften, die das Anwendungsspektrum einschränken können. Hierzu werden Emissionen und Geruchsentwicklung gezählt, die unter bestimmten Temperatur- und Feuchtigkeitsbedingungen auftreten können. Auch bei Verbundmaterialien stellt sich die Frage, welche Einzelkomponenten, Verfahrensschritte oder Kombinationen beider für einen bestimmten Geruch verantwortlich sind.Der Weg zur Geruchsneutralität von Kunststoffen ist generell schwierig, da geeignete Herstellungsmethoden oder auch Zusätze nur in langen Versuchsketten ermittelt werden können und nach wie vor die menschliche Nase wichtiger als alle physikalischelektronischen Messverfahren ist.Die Frage der Herkunft von Gerüchen und nach deren Bedeutung für Wohlbefinden und Gesundheit wird gestellt und zwingt nicht nur die Kunststoffindustrie zur Reaktion. Deshalb sind beide, Kunststoff- und Automobilindustrie, bemüht, auf die Tendenzen des Marktes zu reagieren, und es ist das Ziel der Autohersteller möglichst geruchsneutrale Neuwagen auszuliefern.Possibilities of Odour Measurement and Reduction of Natural Fibre PlasticsThe critical attitude of the German public concerning environmental questions has also invaded the world of odours.The evaluation and reduction of odours when using plastic materials has gained increasing significance in the last years. The packaging industry that produces wrapping materials for food and other consumables was the first to test for odours. During the last years the automobile industry has also shown increased interest in pinpointing and measuring odours, not only because of the increased usage of natural fibre reinforced plastics in car interiors, but also because of the general increase of concern over clean air.Natural fibre reinforced plastics, besides having advantages compared to glass- and carbon reinforced materials (mechanical properties/weight, CO2-equilibrium) also have properties that limit their application possibilities. Emissions and unpleasant odours at certain temperature and humidity conditions are of concern. To determine the origin of odour in bonded materials the single component, production step or their combination causing it has to be found.To achieve odour neutrality in plastics is difficult since production methods or additives can only be determined through prolonged testing and where the human nose is still more important than all the physical electronic measuring methods.The origin of odours and their importance for the well being and health of the population is questioned and forces not only the plastics industry to react. The is why both, plastics- and automobile industries are trying to react to the tendencies of the market place and it is the goal of the auto industry to deliver the most odour-neutral new car.

ABSTRACT Verschiedene Glasfasertypen weisen gegenüber aggressiven Umgebungsmedien eine unterschiedliche Chemikalienresistenz auf. Durch die Einwirkung saurer oder alkalischer Medien können einige Elementarglasfasern ausgelaugt werden, was sich optisch verfolgen lassen kann, andere Glasfasern wiederum zeigen kaum optische Veränderungen. Mit Hilfe der Röntgenmikroanalyse besteht nun die Möglichkeit die durch den Auslaugprozeß hervorgerufene chemische Veränderung der Glasfaserzusammensetzung verschiedener Typen quantitativ bzw. semiquantitativ zu erfassen. Dadurch lassen sich Korrosionsvorgänge an einzelnen Elementarglasfasern besser beschreiben als bisher.Investigations of the Local Composition of Glass Fibers with the Help of the Scanning Electron MicroanalysisVarious glass-fiber types show different chemical resistance in the surrounding of aggressive media. Through the influence of inorganic acid or alkali media certain elementary glass fibres can be leached. This effect can be seen optically in some kinds of glass-fibers. Other glass-fiber types show no optical change in the surface, although there is an aggressive attack Now it is possible to understand the leaching process in glass-fibers with the help of the scanning electron microanalysis. In that way corrosion procedures of various glass-fiber types can be better described.