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Abstract. In this paper, acoustic emission (AE) monitoring with a wavelet-based signal processing technique is developed to detect the damage types during mode I delamination on glass/polyester composite materials. Two types of specimen at different midplane layups, woven/woven (T3) and unidirectional/unidirectional (T5), leading to different levels of damage evolution, were studied. Double cantilever beam (DCB) is applied to simulate delamination process for all specimens. Firstly, the obtained AE signals are decomposed into various wavelet levels. Each level includes detail and approximation that are called components and related to a specific frequency range. Secondly, the energy distribution criterion is applied to find the more significant components each one of which is in relation to a distinct type of damage. The results show that the energy of AE signals has been concentrated in three significant components for both of the specimens. There is a difference in energy distribution of similar components of two specimens. It indicates that there is a dissimilar dominant damage mechanism for two different interfaces during the delamination process. Additionally, the microscopic observation (SEM) is used to determine how the different fracture mechanisms are related to the dominant corresponding wavelet components.

A bis‐IndZrCl2 catalyst was synthesized and used for ethylene homo‐ and copolymerization. The activity of the catalyst increases with increasing Al/Zr ratio; optimum activity was reached at 60 °C. $\overline M _{\rm v}$ of the polymer decreased as the polymerization temperature increased; increasing reaction pressure increased both $\overline M _{\rm v}$ and catalyst activity. The copolymerization of ethylene with different α‐olefins was studied using the same catalyst system. The results indicate that under identical conditions there was a general decrease in the rate of polymerization as compared to the homopolymerization. The CCD and the lamellar thickness were investigated using DSC. The heterogeneity of the CCD increased with increasing comonomer content and molar mass.magnified image

The reinforcing effect of high structure carbon black (HSCB) and multi‐walled carbon nanotubes (MWCNTs) on natural rubber/styrene‐butadiene rubber blend processed using mechanical mixing was comparatively investigated. In‐depth analysis by dynamic mechanical analysis, the Eggers − Schummer model and Medalia's relationship showed that HSCB aggregates provided large internal pores leading to significant immobilized macromolecules in filled rubber. Additionally, a tubular immobilized rubber layer with a thickness of 8 nm was estimated for the rubber/MWCNT system based on dynamic mechanical analysis data. The mechanical performance of the HSCB filled blend was higher than that of the MWCNT filled blend at the same loading which was correlated to its higher bound rubber content. Both bound rubber content and filler anisotropy were found to govern the overall mechanical properties of rubber/MWCNT composites. Stress softening was correlated with rupture energy suggesting hysteretic failure mechanisms in both MWCNT and HSCB filled rubbers. © 2015 Society of Chemical Industry