Strength Of Glass-reinforced Plastics Research Articles

Glass-reinforced plastics based on matrices combining thermoplastics and thermosetting plastics

The conditions of fabrication and the physicomechanical properties of glass-reinforced plastics based on polysulfone combined in different ratios with epoxy resin and Rolivsan were investigated. It was found that realization of the strength of the fibers in glass-reinforced plastics based on three types of binders and mixtures of them at room temperature is approximately the same. The lower strength of glass-reinforced plastics based on polysulfone is determined by the lower concentration of fibers. Modification of thermosetting plastics with polysulfone significantly increases (by 5–8 times) the specific energy of delamination of the glass-reinforced plastics G1c, which should be manifested by an increase in their crack resistance and other operating characteristics. Modification of ED-20 with polysulfone and polysulfone with Rolivsan significantly increases the glass transition temperature of the polymer and affects the character of the temperature curves of the strength of the glass-reinforced plastics.

An Interlaminar Shear Test for Fibre-Reinforced Plastics

The measurement of the interlaminar shear strength of glass-reinforced plastic (GRP) laminates is proposed using an offset four-point bend test on a beam where two (P) of the four forces differ from the other two (Q) and the ratio λ = P/Q depends upon the relative positions along the beam. The paper describes the development of this test which appears simpler, more economic and more realistic in many aspects than other test methods. It is demonstrated theoretically and experimentally that the span length (L), thickness (t) and the ratio λ are important test parameters in determining whether the failure is by shear or by flexure. A test rig was designed and constructed to investigate the influence of these parameters and to determine the interlaminar shear strength of a GRP laminate. Specimens were made from polyester resin containing E-glass fibres in the form of chopped strand mat (CSM). Clear and repeatable interlaminar shear failures have been obtained where L/t was relatively small and Λ large. The crack formation mechanism was studied using photography.

Application of Metalliferous Epoxy Chelate Polymers for Composite Production

Abstract Based on the “theory of solidity” of glass reinforced plastics (GRP), the dependence of the mechanical strength of composites containing E-glass (%:54.0 SiO2, 17.5 CaO, 14.0 Al2O3, 8.0 B2O3, 4.5 MgO, 0.6 K2O, 0.2 Fe2O3, 0.1 F2) reinforcement and metalliferous epoxy chelate polymers (MECP) on the mass of the chelate hardeners produced by the reactions of some organic salts of the transition metals (Cu, Co, Cd, Ni, Zn, Fe, Mn) with aliphatic amines as the ligands has been studied. It has been found that the maximal values of the coefficient of solidity (S) corresponding to the maximal mechanical strength of GRP can be reached when 1 mol diglycidyl ether or Bisphenol-A is cured by 0.14 mol of the hardeners. Analysis of the dependence of GRP strength properties on the structures of chelate hardeners showed a predominant influence of the organic salt anion and, to a lesser extent, the metal cations. To a much lesser degree, the ligands can be explained by the dependence of the adhesional strength of t...

Variation of the strength of glass-reinforced plastic in thermal aging

Variation of the strength of glass-reinforced plastic in thermal aging

Experimental investigation of the strength of glass-reinforced plastics in biaxial compression in three planes of symmetry

Glass-reinforced plastics (GRP) with fiber (wound) and fabric (hot-molded textolites) reinforcement have been investigated in biaxial compression in the three planes of symmetry. The high strength in biaxial compression in the transverse plane, observed for all the GRP investigated, is explained. A method of investigating the tensile strength of the fiber components of the GRP from the results of testing a unidirectional composite in biaxial compression in the transverse plane is proposed. The possibility of a nondestructive estimation of the strength of GRP in biaxial compression at an arbitrary stress ratio is demonstrated.

Effect of local defects on strength of glass-reinforced plastics

Effect of local defects on strength of glass-reinforced plastics

Possibilities of a nondestructive one-parameter method of checking the strength of anisotropic glass-reinforced plastics in uniaxial compression

A nondestructive method of checking the strength of glass-reinforced plastics (GRP) in finished products is proposed. This method is based on the correlation, investigated by the authors, between the modulus of elasticity and the compressive strength determined by a standard method. Various orientations in the plane of reinforcement of glass-reinforced plastics with different ratios of the orthogonally arranged fibers are investigated. It is proposed to determine the modulus of elasticity from the propagation velocity of an ultrasonic pulse measured under conditions of one-sided access to the surface of the product.

Fatigue strength of glass-reinforced plastics (GRP) in shear in the plane of reinforcement

The results of an investigation of the fatigue strength of three grades of glass-reinforced plastic are described. It is shown that cyclic loading with gradually increasing stress amplitude can be used to determine the fatigue strength at a given ambient temperature and loading frequency.

Resistance of glass-reinforced plastics to long-term shear failure

The time dependencies of the strength of glass-reinforced plastics in shear under steady, continuous and alternating loads are examined. Failure under steady and continuous loading is depicted by means of an exponential model of the build-up of damage.

Investigation of the adhesion strength of carbamide resins

The adhesion of carbamide resin to clean or treated fiber glass surfaces has been determined. The effect of this adhesion on the strength of glass-reinforced plastics is examined.

Choice of optimal structure of glass laminates with random reinforcement. I

The effect of structural parameters — length, diameter, and distribution of the reinforcing elements — on the mechanical characteristics of glass-reinforced plastics is investigated with reference to the case of glass laminates with randomly distributed, straight, uncut glass fibers in parallel planes. It is shown that the reduced strength of these laminates as compared with unidirectional material is associated with the redistribution of the load between the fibers and the resin and the relative reduction in the number of fibers in the cross section. A formula is proposed for estimating the strength of glass-reinforced plastics with a random distribution of the fibers in parallel planes.

Statistical strength of glass-reinforced plastics

The failure of glass-reinforced plastics is treated as an aggregate of successive failures of the individual fibers. A method of estimating the statistical strength from the distribution curve is proposed.

Effect of certain technical and geometric factors on the properties of glass-reinforced plastics

Experimental data are used as the basis for a discussion of some of the technical factors affecting the strength of filament-wound glass-reinforced plastics (GRP): winding speed, tension on the glass, life of resin. A relationship between the strength of GRP and these factors is demonstrated. The effect of the thickness and diameter of the test piece on the tensile strength of GRP material is examined.

Estimation of the stability of the strength of glass-reinforced plastics in conical shells

On the basis of a statistical analysis of the test data it is shown that there is a difference between the mechanical characteristics (in tension and compression) of laminated glass-reinforced plastics obtained under laboratory and industrial conditions by impregnation under pressure in a closed mold. The stability of the strength properties of the glass-reinforced plastic in various conical shells, produced in large batches, is considered. Certain experimental relations between the material properties and the total number of shells produced are also established.

Statistical analysis of the results of humidity-temperature tests of glass reinforced plastics (GRP)

The effect of moisture and temperature factors on the strength of glass-reinforced plastics (GRP) is examined. In view of the considerable dispersion of the experimental data, a statistical method is used for analyzing the test results. The tensile strength distribution law for KAST-V glass laminate under various humidity and temperature conditions is analyzed.

Study of the strength of glass-reinforced plastics in the plane stress state

The method and results of an experimental study of the limit plane stress state of glass-reinforced plastics are discussed. A description is given of a special apparatus for testing tubular specimens under hydrostatic pressure, longitudinal load, and twisting moments in conditions of proportional (simple) loading. It is shown that the experimental results are in good agreement with theoretical calculations based on the theory of the strength of anisotropic materials proposed in [1].

Long-time static strength of glass-reinforced plastics in oil media

Long-time static strength of glass-reinforced plastics in oil media

A study of the causes of the reduced strength of glass-reinforced phenolformaldehyde plastics

A study of the curing kinetics of phenolformaldehyde resin in the presence of glass and quartz has shown that one of the chief causes of the reduced strength of glass-reinforced plastics based on phenol-formal-dehyde resin is the difference in the rate and degree of cure in layers close to the fibers and in the bulk of the resin. This is caused by the presence on the surface of the fibers of a hydrate sheath with increased concentration of hydroxyl ions and by the presence of hydrogen bonds between the oxyphenyl groups of the resin and the silanol groups on the surface of the fibers. Chemical treatment of the glass fibers has the effect of diminishing those factors responsible for the reduced rate and degree of cure, and in spite of the lower surface energy of the fibers, the strength of the glass-reinforced plastic increases.

Effect of reinforcing elements on the deformation and strength of glass-reinforced plastics in tension

The problem of extension of a bar of constant cross section containing reinforcing elements in the form of rods arranged parallel to the generators of the lateral surface is considered. A solution is obtained by the Muskhelishvili method. This solution is analyzed and approximate formulas are proposed for the averaged characteristics of materials (especially glass-reinforced plastics) as a function of the relative contents and mechanical properties of the components. The formulas obtained closely reflect a number of known experimental facts.

Strength of glass-reinforced plastics in the complex stress state

A new criterion of strength is proposed for anisotropic materials of the glass-reinforced plastic type. This criterion takes into account not only the different ultimate strengths in tension and compression in each direction but also the dependence of the ultimate shear strengths on the sign (direction) of the shear stresses. The criterion is given in tensor invariant form, so that it can be rewritten for any direction of the glass fibers. The criteria proposed by other authors, in particular, R. Hill's condition of plasticity [1], follow from the new generalized criterion as special cases. The results of experiments conducted both by the authors of the present article and by other investigators provide good confirmation of the proposed criterion.