ABSTRACT:Correlation between the morphology and the impact toughness was studied for ternary-phase polypropylene (PP)/glass bead (GB)/ethylene-propylene rubber (EPR) composites containing 5-40 vol % of rigid filler at a fixed volume fraction ratio EPR/GB equal to 0.33. The three following types of phase morphology were obtained: (1) separate dispersion of phases and weak GB-PP adhesion; (2) separate dispersion of phases and high GB-PP adhesion; and (3) encapsulation of GB particles by elastomer shell. Maleated PP or EPR was used for the preparation of second and third types of composites, respectively. Binary composites with either rigid or rubbery phases were prepared as model systems. Young's modulus values of composites containing GB encapsulated by a soft interlayer stay close to neat PP modulus and are located in the bounds corresponding to ternary systems with phase-separate distribution and rubber-modified PP. Notched impact strength was measured by Izod and three-point bending tests. Systems with the phase-separate distribution both with weak and with high adhesion exhibit quasi-brittle fracture. The encapsulation of GB particles by elastomer results in significant improvement of the toughness. An increase in core-shell inclusion fraction leads to intense matrix yielding within a specimen bulk and brittle-ductile transition similar to the rubber-toughened PP. A criterion of brittle-ductile transition was proposed on the basis of load-time curve analysis, which is an accumulation of critical plastic deformation on a crack initiation stage. The stress of start of local failure microprocesses at the inclusion-matrix boundary was found to play the dominating role in energy-dissipating mechanisms. The lowering of the stress at which a local matrix yielding starts at elastomer shell-PP interface compared to the stress of GB debonding is a main source of intensive energy adsorption at the initiation stage in the system with encapsulated GB. The optimal stiffness-toughness balance can be obtained by coating the rigid particles with an elastomer shell.

The role of rigid particle size in the deformation and fracture behavior of filled semicrystalline polymer was investigated with systems based on polypropylene (PP) and model rigid fillers [glass beads, Al(OH) 3 ]. The regularities of the influence of particle content and size on the microdeformation mechanisms and fracture toughness of the composites at low and high loading rates were found. The existence of the optimal particle size for fixed filler content promoting both maximum ultimate elongation of the composite at the tensile and maximum toughness at impact test was shown. The decrease of the toughening effect with both decreasing and increasing particle size regarding the optimal one was explained by dual role of particle size, correspondingly as either "adhesive" or "geometric" factors of fracture. The adhesive factor is due by the increase of debonding stress with the particle size decrease and the voiding difficulty resulting in the restriction of plastic flow. The geometric factor consists in the dramatic decrease of the composite strength at break if the void size exceeds the critical size of defect (for a given matrix) at which the crack initiation occurs. The analysis of the filled polymer toughness dependencies upon the particle size revealed that a capacity of rigid particles for the energy dissipation at the high loading rate depends on two factors: (i) ability of the dispersed particles to detach from matrix and to initiate the matrix local shear yielding at the vicinity of the voids and (ii) the size of the voids forming. Based on the findings it was concluded that the optimal minimal rigid particle size for the polymer toughening should answer the two main requirements: (i) to be smaller than the size of defect dangerous for polymer fracture and (ii) to have low debonding stress (essentially lower compared to the polymer matrix yield stress).

The proposed study focuses on the inverse and forward kinematic analysis of a novel 6-DOF parallel manipulator with a circular guide. In comparison with the known schemes of such manipulators, the structure of the proposed one excludes the collision of carriages when they move along the circular guide. This is achieved by using cranks (links that provide an unlimited rotational angle) in the manipulator kinematic chains. In this case, all drives stay fixed on the base. The kinematic analysis provides analytical relationships between the end-effector coordinates and six controlled movements in drives (driven coordinates). Examples demonstrate the implementation of the suggested algorithms. For the inverse kinematics, the solution is found given the position and orientation of the end-effector. For the forward kinematics, various assembly modes of the manipulator are obtained for the same given values of the driven coordinates. The study also discusses how to choose the links lengths to maximize the rotational capabilities of the end-effector and provides a calculation of such capabilities for the chosen manipulator design.

We represent a classical Maxwell-Bloch equation and relate it to positive part of the AKNS hierarchy in geometrical terms. The Maxwell-Bloch evolution is given by an infinitesimal action of a nilpotent subalgebra n+ of affine Lie algebra [Formula: see text] on a Maxwell–Bloch phase space treated as a homogeneous space of n+. A space of local integrals of motion is described using cohomology methods. We show that Hamiltonian flows associated with the Maxwell–Bloch local integrals of motion (i.e. positive AKNS flows) are identified with an infinitesimal action of an Abelian subalgebra of the nilpotent subalgebra n− on a Maxwell–Bloch phase space. Possibilities of quantization and lattice setting of Maxwell–Bloch equation are discussed.

The objective of this study is to investigate the use of an air atmospheric plasma jet for the treatment of sized basalt fibers, used in the fabrication of continuous fiber‐reinforced polypropylene filaments. The plasma treatments were carried out both at a laboratory scale, as well as in‐line during the production of fiber‐reinforced filaments. The latter was carried out at a fiber processing speeds of approximately 15 m/s, just immediately before the polymer coating of the fiber by extrusion. After the air plasma treatment, the water contact angle of the sized basalt fiber decreased from 86° to <10°. X‐ray photoelectron spectroscopy analysis demonstrated that the treatment yielded enhanced levels of oxygen functionality on the fiber surface. After coating with polypropylene, it was observed that there was consistently more homogeneous polymer layer deposited onto the plasma‐activated fiber, compared with that on the unactivated control fiber. The resulting polymer filament with embedded basalt fiber was used to fabricate mechanical test specimens by three‐dimensional printing (fused filament fabrication method). Both three‐point bending tests and short beam strength tests were performed. A comparison study was carried out between test specimens fabricated using sized basalt fiber, with and without the plasma pretreatment. The flexural modulus and maximum shear stress were found to increase by 12% and 13%, respectively, for composite's fabricated using the plasma pretreated basalt fibers. This increased mechanical strength is likely to be due to an increase in interfacial bond strength between the polymer and fiber, with an associated reduction in the level of air incorporation around the basalt filaments as demonstrated using computed tomography analysis.