Cover:The picture on the cover shows a TEM image of the phase morphology and the mechanical properties of PMMA/SiO 2 nanocomposites. The indentation fracture mechanics is quite well applicable for evaluation of fracture toughness in combination with per-colation of the bound polymer layers around the SiO 2 particles.

An extended version of Strutinsky's macro~microscopic method is used to calculate effective potential energies for rotating, excited heavy compound nuclei undergoing fission.Nuclear deformation is parameterized in terms of Lawrence's family of shapes. A two~center single~particle potential corresponding to these shapes is employed, with BCS pairing added.Statistical excitation is introduced by temperature~ dependent occupation of (quasi-) particle energy levels. We calculate shell corrections to the energy, the free energy and the entropy as functions of deformation and temperature. The We have also calculated the effective potential for constant entropy rather than constant temperature. Although this isentropic process physically is more appropriate than the isothermal ocess, it has not been treated before. For the same amount of excitation energy in the spherical state of the compound nucleus, the isentropic barriers turn out higher than the isothermal ones. For both processes we have extracted the critical angular momentum (defined as the one for which the barrier approximately vanishes) as a function of excitation.

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Summary: Based on the results from agglomerate‐free PMMA nanocomposites with 10 and 20 wt.‐% spherical SiO2 nanoparticles, it has been shown that indentation fracture mechanics is a straightforward, powerful, cost‐effective and time‐effective tool for analyzing the fracture resistance of novel polymer materials, such as brittle nanostructured polymer‐ceramic hybrids. In contrast to pure PMMA, the R‐curve effect, i.e., the enhancement in crack resistance as a function of crack size, was not observed in the nanocomposites investigated. Fracture toughness was found to depend on the SiO2 nanoparticle content, and the maximum value was observed at 10 wt.‐%. A significant reduction in fracture toughness occurred at 20 wt.‐% SiO2 nanoparticles, which is associated with a percolation of the bound layers (interfacial layers) around the SiO2 particles. From DSC data, the thickness of the interfacial polymer layer was estimated to be about 9 nm.Hardness, elastic modulus and fracture toughness of PMMA/SiO2 composites as a function of nanoparticle fraction.magnified imageHardness, elastic modulus and fracture toughness of PMMA/SiO2 composites as a function of nanoparticle fraction.

Relationships between phase morphology and mechanical deformation processes in various electrospun polymer nanocomposite nanofibres (PNCNFs) containing different types of one-, two- and three-dimensional nanofiller have been investigated by transmission electron microscopy using in situ tensile techniques. From the study of the phase structure of electrospun PNCNFs, two morphological standard types are classified for the analysis of deformation mechanisms: the binary system (polymer matrix and nanofillers), and the ternary system (polymer matrix, nanofillers and nanopores on the fibres surface). According to these categories, deformation processes have been characterized, and different schematic models for these processes are proposed. The finding of importance in the present work is a brittle-to-ductile transition in polymer nanocomposite fibres during in situ tensile deformation processes. This unique feature in the deformation behaviour of electrospun PNCNFs provides an optimal balance of stiffness, strength and toughness for use as reinforcing elements in a polymer based composite of a new kind.