Development of fibre-metal laminates for improved impact performance

An analytical and experimental investigation into the low-velocity behaviour of GLARE Fibre-Metal Laminates (FMLs) has been performed. A quasi-static approach was developed to estimate the perforation energy absorbed between the constituents of GLARE. The analysis considered contact area increase during perforation and strain rate effect on material properties. Particular attention was paid to the effect of ply-angle orientation and aluminium position. Predicted maximum impact force, maximum displacement, and perforation energy related to impact velocity were within 10% of test results. Stacking composite plies oriented along the diagonal of the plate with more than 2 aluminium layers leads to a more impact resistant FML. The generic nature of the developed methodology can support the optimization of high-performance FML concepts.     

Study of the fire resistant behavior of unfilled and carbon nanofibers reinforced polybenzimidazole coating for structural applications

With increasing interest in epoxy‐based carbon fiber composites for structural applications, it is important to improve the fire resistant properties of these materials. The fire resistant performance of these materials can be improved either by using high performance epoxy resin for manufacturing carbon fiber composite or by protecting the previously used epoxy‐based composite with some fire resistant coating. In this context, work is carried out to evaluate the fire resistance performance of recently emerged high performance polybenzimidazole (PBI) when used as a coating material. Furthermore, the effect of carbon nanofibers (CNFs) on fire resistant properties of inherently flame retardant PBI coating was studied. Thermogravimetric analysis of carbon/epoxy composite, unfilled PBI and nano‐filled PBI shows that the carbon/epoxy composite maintained its thermal stability up to a temperature of 400°C and afterwards showed a large decrease in mass, while both unfilled PBI and nano‐filled PBI have shown thermal stability up to a temperature of 575°C corresponding to only 11% weight loss. Cone calorimeter test results show that unfilled PBI coating did not improve the fire retardant performance of carbon/epoxy composite. Conversely, nano‐filled PBI coating has shown a significant improvement in fire retardant performance of the carbon/epoxy composite in terms of increased ignition time, reduced average and peak heat release rate and reduced smoke and carbon monoxide emission. These results indicate that addition of carbon nanofibers to inherently flame retardant coating can significantly be helpful for improving the fire resistance performance of composite materials even with low coating thickness. Copyright © 2013 John Wiley & Sons, Ltd.     

Fluktuierende cyclopolyenyl---kobalt(I)-komplexe mit asymetrischer ring---kobalt-bindung

[Co(1-3-η-C₇H₉)(CO)₂(PPh₃)] and [Co(1,2,5,6,7-η-C₈H₉)(C₈H₈] exhibit in solution interconversion of their enantiomorphous structures generated by the asymetric ring---cobalt bonds. This stereochemical nonrigid behaviour has been studied by means of the ¹H nuclear magnetic double resonance method evaluating the activation parameters of the interconversion reactions.     

Einstein relation in n-i-p-i and microstructures of nonlinear optical, optoelectronic and related materials: Simplified theory, relative comparison and suggestions for an experimental determination

We investigate the Einstein relation for the diffusivity-mobility ratio (DMR) for n-i-p-i and the microstructures of nonlinear optical compounds on the basis of a newly formulated electron dispersion law. The corresponding results for III-V, ternary and quaternary materials form a special case of our generalized analysis. The respective DMRs for II-VI, IV-VI and stressed materials have been studied. It has been found that taking CdGeAs₂, Cd₃As₂, InAs, InSb, Hg_1−xCd_xTe, In_1−xGa_xAs_yP_1−y lattices matched to InP, CdS, PbTe, PbSnTe and Pb_1−xSn_xSe and stressed InSb as examples that the DMR increases with increasing electron concentration in various manners with different numerical magnitudes which reflect the different signatures of the n-i-p-i systems and the corresponding microstructures. We have suggested an experimental method of determining the DMR in this case and the present simplified analysis is in agreement with the suggested relationship. In addition, our results find three applications in the field of quantum effect devices.     

On the simulation of panel distortions due to hot curing adhesives

Hot curing one-part adhesives are often used to bond car body shells. The cure process of the adhesive, however, can lead to distortions, i.e. unwanted, visible deformations of the adherends. In case of outer car panels, these distortions are considered as visual defects, even though the structural integrity might not be affected. In order to avoid distortions by a proper control of the bonding process, a thorough understanding of the development of distortions is necessary. Finite element simulations can help to gain insight into this development. In this work, a simulation model is proposed and used to study the appearance of distortions in a steel sheet over different temperature cycles. The model takes chemical shrinkage and thermal deformation as well as gelation and stress relaxation into account. It was found that the heating rate can affect distortions. Lowering the cure temperature only lowers distortions for high temperature rates. Low heating rates can reduce distortions.     

π-Olefin-iridium-komplexe : II. Synthese und dynamisches verhalten von bis(η4-Cyclodien)-hydrido-iridium(I)-komplexen

By reaction of [Ir(COD)Cl]₂ (COD = 1,5-cyclooctadiene) with i-C₃H₇MgBr in the presence of cyclic dienes, complexes of the type [IrH(COD)L] (L = 1,3-cyclohexadiene, 2-methyl-],3-cyclohexadiene, 5-ethyl-1,3-cyclohexadiene, 1,3-cycloheptadiene) are obtained. The system IrCl₃/i-C₃H₇MgBr/1,3-C₆H₈ yields [IrH(1,3-C₆H₈)₂]. According to NMR spectroscopic investigations the pure hydrido forms exist in solution only at low temperatures while at room temperature dynamic H-addition—elimination equilibria of the type [IrH(η⁴-diene)(COD)] ? [Ir(η³-enyl)(COD)] and [IrH(η⁴-1,3-C₆H₈)₂] ? [Ir(η³-C₆H₉)-(η⁴-1,3-C₆H₈)], respectively, are observed; the hydrogen at the iridium atom is thereby transferred to the endo positions of the diene ligands.