Yu. A. Gorbatkina

Comparison of Fracture Energies of Epoxy-polysulfone Matrices and Unidirectional Composites Based on Them

The fracture energies of modified epoxy matrices and unidirectional glass (GFRP)-, organic (OFRP)-, and carbon (CFRP)-fiber-reinforced plastics based on them are compared. The unidirectional composites were fabricated by winding. Epoxy-polysulfone compositions were used as matrices containing from 5 to 20 wt.% of PSK-1 polysulfone. The matrices were cured with triethanolaminotitanate. It is shown that the fracture mechanisms of GFRP, OFRP, and CFRP in shear differ, which is supposedly related to the nature of fibers. The fracture energy of reinforced plastics is mainly determined by the impact strength of matrix. The delamination energy GIRcm of GFRP, OFRP, and CFRP increased monotonically with content of polysulfone in the matrix. A marked growth in GIRcm was observed at a content of polysulfone exceeding 10 wt.%. The crack resistance of the composites under investigation increased two times. The fracture toughness of GFRP and OFRP was 3-4 times higher than that of CFRP at any concentration of polysulfone. A growth in GIRm of the matrices started when the content of PSK-1 exceeded 5 wt.%, and at 15-20 wt.% of PSK-1, the values of GIRm increased four times. In all the cases investigated, a correlation between the crack resistance of reinforced plastics and that of polymeric matrices was observed.

Organic fiber reinforced plastics based on complex hybrid matrices including polysulfone and carbon nanotubes as modifiers of epoxy resins

Organic Fiber Reinforced Plastics (OFRP) based on aramid fibers are as a rule used in constructions working under extremal conditions. In view of this, the possibility of increasing the resistance of OFRP to destruction by modifying matrices with thermoplastic polymers and carbon nanotubes (CNTs) offers much promise. In this work, we present the results obtained in a study of the properties of OFRP based on Rusar fibers and epoxy matrices containing either CNTs or a thermoplastic (PSK-1 polysulfone) or both these components simultaneously. The data obtained substantiate the possibility of using epoxypolysulfone matrices for the preparation of wound composites. This modification noticeably increases crack and impact resistance of OFRP based on aramid fibers without decreasing the glass transition temperature, as when matrices are plasticized by rubber and active diluents. The strongest effect of polysulfone introduced into an epoxy matrix is observed at a large (20 wt %) content of PSK-1. The modification of epoxypolysulfone matrices by CNTs also increases the shear strength of OFRP and almost does not change the fracture toughness and compression strength. The introduction of CNTs into epoxy matrices is less effective and can increase crack growth resistance of OFRP by approximately 30% only at a large (1%) content of CNTs. Small CNT admixtures (0.3–0.6%) do not influence the fracture toughness. Possible mechanisms of the changes observed are considered.

ADHESION OF DISPERSEDLY FILLED EPOXIDES TO SOLIDS

The adhesive strength τ of dispersedly filled epoxy resin/150-μm steel wire joints as a function of filler concentration C has been studied. The fillers were mineral and carbon-containing powders with micron-, submicron-, and nanosize particles (aerosil, clay, aluminum oxides, industrial carbon black, schungite, and carbon nanotubes). It is shown that, in many cases, the τ–C relationships are described by curves with a maximum as the filler concentration C increases. Mechanisms responsible for the synergism of the adhesive strength are considered.

Rheological and Physicomechanical Properties of Epoxy-Polyetherimide Compositions

The effect of polyetherimide on the viscosity and physicomechanical characteristics of epoxides was investigated. It is shown that the introduction of polyetherimide increases the viscosity of the ED-20 oligomer and enables one to increase the crack resistance of cured resin four times, its impact resistance 1.5 times, and the total impact energy two times. The improvement in these properties is related to structural changes of the composition with increasing concentration of the thermoplastic.

The kinetics of thermal degradation and the structure of bisphenol-A epoxy binder modified by active plasticizer

The kinetics of thermal degradation and the molecular mobility of a bisphenol-A epoxy binder obtained by curing the oligomer ED-20 in the presence of various amounts of epoxidized diethylene glycol as an active plasticizer were studied. It was shown that polyepoxies modified with this plasticizer formed a one-phase system; as the plasticizer mass fraction is increased, the properties of the binder change—the glass transition temperature decreases while the spin-spin relaxation times and the rate constants of thermal degradation increase, a result that is due to an increase in the length and molecular mobility of interjunction chains in modified samples.

Adhesive strength of bonds of polymers with carbon fibres at different loading rates

AbstractThe effect of the loading rate on the strength of the interface of bonds of UKN-5000-P carbon fibres ≈7 μm in diameter with thermosetting (EDT-10 epoxy binder) and thermoplastic (PSK-1 polyarylene sulfone) matrices was investigated. The adhesive strength τ0 of the bonds was determined in shear of a monofilament relative to the polymer layer (pull-out method). It was found that the adhesive strength τ0 of the systems investigated is a linear function of the logarithm of the rate of increase in shear stressesn

Change of adhesion properties of epoxy oligomer modified by polyarylene ether ketone in the process of curing

dot tau :tau _0 = C_1 + C_2 log dot tau

Carbon nanotubes as modifiers in epoxypolysulfone matrices for wound organic-fiber-reinforced plastics

n. Constants C2 characterizing the kinetics of failure of the interface were determined. A comparison of the data obtained with previously published results showed that in quasistatic loading, the linear correlation between τ0 and log holds for polymer—fibre bonds with different components.