Functionalised multi‐walled carbon nanotubes for epoxy nanocomposites with improved performance

BACKGROUND: Carbon nanotubes (CNTs) are fast becoming key components in the production of high‐strength composite materials. Two methods to prepare nanocomposites by covalent bonding between an epoxy matrix and functionalised CNTs that acted as cross‐linkers during polymerisation were investigated. RESULTS: In the standard method, 1 wt% functionalised CNTs was dispersed in epoxy, hardener was added and the composite was cured. In the masterbatch approach, 1 wt% functionalised CNTs was mixed with epoxy in the presence of triethylamine accelerator, then cured. This yielded partially cured epoxy; additional hardener was required to achieve complete curing. Improvements were observed in storage modulus (E′), flexural modulus (E_B), wear resistance and hardness. Thermal stability did not change appreciably for samples prepared by either the standard or masterbatch methods. Variations in the results obtained as a function of preparation method, functionalised CNTs and hardener used are discussed. CONCLUSION: Epoxy nanocomposites having improved mechanical properties were obtained by incorporating functionalised CNTs. Better interaction between the epoxy and CNT was achieved using the masterbatch method; this was attributed to covalent bonding between the CNTs and epoxy. However, optimisation of the CNTs, accelerator and hardener used in composite preparation is required to obtain improved physical properties. Copyright © 2009 Society of Chemical Industry     

Failure mechanisms and qualification testing of passive components

New electronic architectures and mechatronic integration in automotive and oil-field applications lead to increasing requirements concerning operating temperatures and vibration levels. At the same time, reliability and lifetime have to fulfil strong demands.In the European funded project PROCURE (Program for the development of passive devices used in rough environments) a generic spectrum of passive components needed for electronic control units has been developed. The failure mechanisms, the technological challenges, and the test requirements are highlighted below.     

The Bauschinger effect in the supercooled austenite of SAE 52100 steel

During the heat treatment and the welding of steel components, the interactions between the thermal and phase transformation strains result in cyclic loading of the component, which often results in plastic deformation. Although this has long been a well-known fact, the cyclic hardening behavior of supercooled austenite was not investigated up to now. In this study, tension–compression tests were performed on the supercooled austenite of SAE 52100 ball bearing steel at several temperatures using Gleeble3500® thermomechanical testing machine. The results were compared with conventional hardening models used in heat treatment and welding simulation. The results indicate that the metastable austenite exhibits a complicated cyclic hardening behavior that can only be partially reproduced by commercial simulation software. In the outlook, it is concluded that more complicated cyclic hardening models should be implemented for better prediction of distortion and residual stresses after heat treatment or welding.     

When and How Narratives Persuade: The Role of Suspension of Disbelief in Didactic Versus Hedonic Processing of a Candidate Film

This study examined how exaggeration in a biographical film about a political candidate affects attitudes toward the candidate, as well as how this attitudinal effect is contingent on goal‐oriented processing strategies and mediated by suspension of disbelief (SOD), a tolerant audience response to a perceived lack of realism. On the basis of a randomized 2 (portrayal of the candidate: mildly positive vs. exaggerated) by 2 (modal processing strategy: didactic vs. hedonic) factorial experiment, we found an indirect effect for exaggeration on attitude through SOD as a function of processing strategy. Implications of the study findings for narrative persuasion theory and research are discussed.