Discrete Element Method for the thermal field: Proof of concept and determination of the material parameters

The physical behaviour of materials and complicated components is nowadays numerically predicted by using the Finite Element Method (FEM). Another method, older than the finite element idea, is the Discrete Element Method (DEM), with which it is possible to make continuum-based calculations not only in the mechanical field but also in the thermal field, as will be shown in this paper.One major drawback of the FEM is that continuum-based methods are unable to include the stochastically distributed microscopic effects in the macroscopically oriented calculations. The Discrete Element Method is one method with which these effects can be considered.For making realistic fracture and life time predictions for components at high temperatures, it is important to adapt the DEM for the thermal field. This paper describes the mathematical proof of the 2D Discrete Element Method (or Lattice Model) for the thermal field. It will specifically be shown that the heat flux inside the framework can be transferred to the heat conduction equation. Furthermore, some examples demonstrate how the heat flux can be calculated with this method and how the corresponding material parameters are found and implemented. Also, as will be shown in this paper, anisotropic or orthotropic heat flux effects can be integrated in the DEM model.     

Synthesis,characterization, and cure of allyl and propargyl functionalized indene as a thermoset composite matrix resin

Two highly functionalized resins were synthesized by the phase transfer reaction of indene with propargyl bromide or allyl chloride in the presence of strong base. The resins consisted of a mixture of tri- and tetrafunctional indenes with 60–80% of the product being tetrafunctional. The allylated (AL) and propargylated (PL) indene resins were thermally cured without added catalysts. Both resins exhibited a broad, highly exothermic cure with a peak energy at 320°C for AL resin and 282°C for PL resin. Thermal degradation of cured AL resin was found to begin at approximately 400°C with a carbon yield of 20% of its initial weight at 1000°C. Carbon yields for cured PL resin were excellent, with 68% retention of weight at 1000°C. Unidirectional, carbon fiber composites were fabricated from the substituted indene resins. AL–carbon fiber composites gave modulus values of 126 GPa and strength values of 967 MPa, while PL–carbon fiber composites gave modulus values of 116 GPa and strength values of 935 MPa in three-point bending tests. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 475–482, 1998     

Oxokohlenstoffe und verwandte Verbindungen. 27. Synthese von Dihydrocyclobuta[a]naphthalen-1,2-dionen und Cyclobuta[a]naphthalen-1,2-dionen durch Anellierung von Alkoxy-(1-alkenyl)benzolen mit 3-Chlor-3-cyclobuten-1,2-dion. Anwendungsbereich und Grenzen

Oxocarbons and Related Compounds. 27. Synthesis of Dihydrocyclobuta[a]naphthalene-1,2-diones and Cyclobuta[a]naphthalene-1,2-diones via Annulation of Alkoxy-(1-alkenyl)benzenes with 3-Chloro-3-cyclobutene-1,2-dione. Scope and Limitations The reaction of alkoxy-(1-alkenyl)benzenes with semisquaric chloride ( 3 ) has been investigated systematically. 1,2-Dialkoxy- and 1-alkoxy'-2-alkoxy″-4-(1-alkenyl)benzenes ( 6a–j ) and ( 11a–i ) react with 3 to give the 3,4-dihydrocyclobuta[a]naphthalene-1,2-diones ( 8a–j ) and ( 12a–i ). Treatment of the dihydrocyclobuta[a]naphthalene-1,2-diones with 1.2 equiv. bromine effects dehydrogenation and affords cyclobuta[a]naphthalene-1,2-diones ( 9a–e ) and ( 13b–f ). Any efforts to extend this annulation reaction to dimethoxy-(1-alkenyl)benzenes with the methoxy groups in other than the 1,2-positions, e. g. 14a, b, 16a, b have been unsuccessful. The reaction of 1,2,3-trimethoxy-4-(1-propenyl) [and 4-(1-butenyl)]-benzenes ( 18a ) and ( 18b ) with semisquaric chloride ( 3 ) leads to the elimination of HCl and CH₃OH and gives 5,6-dimethoxy-3-methyl [and 3-ethyl]-cyclobuta[a]naphthalene-1,2-diones ( 20a ) and ( 20b ). The reaction pathway of this novel annulation reaction is discussed.     

Charge engineering of a protein domain to allow efficient ion-exchange recovery

We have created protein domains with extreme surface charge.These mutated domains allow for ion-exchange chromatographyunder conditions favourable for selective and efficient capture,using Escherichia coli as a host organism. The staphylococcalprotein A-derived domain Z (Z_wt) was used as a scaffold whenconstructing two mutants, Z_basic1 and Z_basic2, with high positivesurface charge. Far-ultraviolet circular dichroism measurementsshowed that they have a secondary structure content comparableto the parental molecule Z_wt. Although melting temperatures(T_m) of the engineered domains were lower than that of the wild-typeZ domain, both mutants could be produced successfully as intracellularfull-length products in E.coli and purified to homogeneity byion-exchange chromatography. Further studies performed on Z_basic1and Z_basic2 showed that they were able to bind to a cation exchangereven at pH values in the 9 to 11 range. A gene fusion betweenZ_basic2 and the acidic human serum albumin binding domain (ABD),derived from streptococcal protein G, was also constructed.The gene product Z_basic2–ABD could be purified using cation-exchangechromatography from a whole cell lysate to more than 90% purity.     

Molecular composites based on thermosetting matrix polymers: Poly(p-phenyleneterephthalamide)-epoxy

Poly(p-phenyleneterephthalamide) (PPTA) reinforced molecular composites that utilize a thermosetting epoxy as the matrix polymer have been prepared by an in situ polymerization process. The properties of these molecular composites were compared with those of Kevlar pulp-filled composites that utilized the same matrix formulation. Study of the curing reactions of these systems using Fourier transform infrared, dynamic mechanical analysis, and nuclear magnetic resonance spectroscopy indicated some differences in the reactivity and ultimate polymer structure of these two systems. A comparison of the properties indicated increased tensile strength, modulus, and heat resistance for the molecularly reinforced material over the conventional fiber-filled system. Examination of the morphology of the molecular composite system showed that aggregated PPTA molecules are formed during the in situ polymerization process. This aggregation phenomenon was found to be due to formation of a liquid crystalline polymer solution during processing and final cure. These findings indicate the possibilities that exist in molecular composite processing for simultaneous control of the properties of the matrix and the reinforcement.     

Interaction of titanium diboride/boron nitride evaporation boats with aluminium

Hexagonal boron nitride/titanium diboride composites are widely used as evaporation boats for aluminium deposition to produce functional and decorative layers on different target materials. The lifetime of such a material is limited mainly by the interaction of the metal with the ceramic substrate, but the corrosion mechanism has still not yet been thoroughly investigated and understood. In this article the corrosion mechanism for the evaporation boats used was investigated using thermodynamic calculations, FESEM, EDX and XRD phase analysis. The analysis showed that hexagonal boron nitride (hBN), which is thermodynamically less stable than TiB₂, is passivated during the application process through the formation of AlN surface layers, whereas the thermodynamically more stable TiB₂ phase dissolves and Ti-rich components precipitate in cooler regions of the evaporation boats.