Thermal deformation of unidirectionally reinforced hybrid composites. Report no. 1

Conclusion We conducted a dilatometric study of three types of hybrid unidirectionally reinforced composites (organic-glass-, organic-carbon-, and carbon-glass-fiber plastics), each of which was represented by several batches differing in the relative content of the two types of fibers. The tests were performed on a specially-designed laboratory prototype. It was shown that, for the materials studied, the coefficient of linear expansion can be controlled by means of hybridization — by combining several types of fibers with positive and negative values of the coefficient of linear expansion in one composite. Analytic expressions for the coefficient that were obtained by generalizing a three-phase model of a two-component composite with isotropic fibers to the case of a hybrid composite with anisotropic fibers satisfactorily describe the experimental data.Translated from Mekhanika Kompozitnykh Materialov, No. 2, pp. 229–236, March–April, 1989.     

Thermal expansion of a composite with a hybrid granular-fibrous filler

Conclusion The thermal deformation of LDPE with a granular-fibrous filler was studied experimentally within a broad temperature range. We analyzed the effect of fillers on characteristics of relaxational transitions in LDPE as determined from dilatometric tests. A method was proposed for calculating the effective CLE of a composite with allowance for aggregation of a powdered filler and the statistical distributions of the length and orientation of the anisotropic fibers. The method was substantiated experimentally. Results were also presented of a theoretical analysis of the effect of the parameters of the fiber distributions f(l.) and (, ) and the relative volume contents of granular and fibrous fillers on _ij for the composite. It was established that aggregation of the granular filler may produce a hybrid effect consisting of maximum suppression of thermal expansion of the binder by the combination filler relative to a two-component composite.Translated from Mekhanika Kompozitnykh Materialov, No. 2, pp. 237–246, March–April, 1989.     

Thermal conductivity of unidirectionally reinforced hybrid composites

Conclusion The thermal conductivity of organic-glass, organic-carbon, and carbon-glass plastic in dependence on the volumetric content of organic, glass, and carbon fibers was experimentally investigated. The solution for transverse thermal conductivity of unidirectional hybrid composite, obtained in [8] by generalizing the method of self-congruence to the case of a triphase model, is in satisfactory agreement with the experimental data.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 817–822, September–October, 1990.     

Thermal deformation of unidirectional hybrid composites. 2

Conclusions A variant of the solution of the problem of the thermorheologically complex temperature strain of a hybrid composite containing viscoelastic thermorheologically simple components with differing functions for temperature-time reduction in addition to elastic components, is proposed. An experimental study is conducted on unidirectional specimens of organic- and glass-fiber-reinforced plastic, organic- and carbon-fiber-reinforced plastic, and carbon- and glass-fiber-reinforced plastic at a constant rate of temperature change in the 20–150 °C range. Satisfactory correspondence is obtained between predicted and experimental data.For previous communication, see [1].Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 969–979, November–December, 1989.     

Nonlinear moisture deformation of a composite with a densified reinforcement

Conclusion An analytical method is presented for estimation moisture deformation of densified in technological pressing wood-based composite material with nonlinear swelling properties. This includes modelling of the processing effects as well as interfacial bonding. By using the multilayer model supported on the laminate analogy the optimum particle alignment has been estimated for a real composite production process.Published in Mekhanika Kompozitnykh Materialov, Vol. 30, No. 3, pp. 314–320, May–June, 1994.     

Elastoplastic deformation of flexible reinforced plates with a reduced shear strength

The problem of the elastoplastic deformation of reinforced plates taking account of their reduced shear strength is formulated in rectangular Cartesian and cylindrical systems of coordinates within the framework of deformation-type constitutive relations based on the first version of Timoshenko's theory. The mechanical behaviour of annular plates with different helical reinforcement structures is investigated and it is shown that the use of classical theory to calculate the elastoplastic bending of relatively thick and, in some cases, relatively thin reinforced plates leads to an unjustified prediction of the compliance of thin-walled composite structures that is too low. The calculations carried out demonstrate the development of considerable shear deformations in the binder of such plates, that have to be taken into account, since it determines the deformation characteristics of the structures studied. The results of calculations obtained using two structural models are compared.     

Non-linear oscillations of a thin-walled composite beam with shear deformation

A geometrically non-linear theory is used to study the dynamic behavior of a thin-walled composite beam. The model is based on a small strain and large rotation and displacements theory, which is formulated through the adoption of a higher-order displacement field and takes into account shear flexibility (bending and warping shear). In the analysis of a weakly nonlinear continuous system, the Ritz’s method is employed to express the problem in terms of generalized coordinates. Then, perturbation method of multiple scales is applied to the reduced system in order to obtain the equations of amplitude and modulation. In this paper, the non-linear 3D oscillations of a simply-supported beam are examined, considering a cross-section having one symmetry axis. Composite is assumed to be made of symmetric balanced laminates and especially orthotropic laminates. The model, which contains both quadratic and cubic non-linearities, is assumed to be in internal resonance condition. Steady-state solution and their stability are investigated by means of the eigenvalues of the Jacobian matrix. The equilibrium solution is governed by the modal coupling and experience a complex behavior composed by saddle noddle, Hopf and double period bifurcations.     

Elastic characteristics of a cement-based composite reinforced with steel grid ribbons

A method is proposed for the estimation of elastic characteristics of a cement mortar orthogonally reinforced with punched steel grid ribbons. The method proposed takes into account the geometry of grids, the distance between ribbons, and the elastic properties of cement mortar and steel.     

Elastic characteristics of a cement-based composite reinforced with steel grid ribbons

A method is proposed for the estimation of elastic characteristics of a cement mortar orthogonally reinforced with punched steel grid ribbons. The method proposed takes into account the geometry of grids, the distance between ribbons, and the elastic properties of cement mortar and steel.Riga Technical University, Riga, LV-1047 Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 173–180, March–April, 1999.     

Prediction of the deformation properties of a polymeric composite with a granular-fibrous filler

Conclusion A variant of calculation of the characteristics of the deformation properties of a hybrid composite containing a complex disperse filler in the form of granular particles and short fibers was proposed. The effect of aggregation of the granular filler, the statistical distributions of the fibers by lengths and orientation in the material, and the anisotropy of the fibers are taken into consideration in the calculation. The statistical distribution of the orientation of the fibers is given by a function proportional to the distance from the center to the surface of a triaxial ellipsoid in the corresponding direction. The uniform random distribution of the fibers in bulk and in the plane is a special case of this distribution. The results of the analysis of the effect of the parameters of the statistical distributions of the length and orientation of short fibers on the elasticity characteristics of a composite are reported. The dependence of the creep of the composite on the ratio of the concentration of the components of the complex filler was determined, and the efficiency of partial replacement of a granular filler by a short-fiber filler to inhibit creep of the composite was demonstrated. The possibilities of predicting the long-term creep were experimentally confirmed on the example of LDPE filled with ground limestone and short glass fibers.Presented at the Sixth All-Union Conference on the Mechanics of Polymer and Composite Materials (Riga, November, 1986).Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 898–909, September–October, 1987.     

Elastic displacements of a cement-based composite beam reinforced with punched steel grids

Using Mohr's method, a procedure is proposed for calculating the elastic displacements of a cement-based composite beam reinforced with punched steel grid ribbons. The approach proposed takes into account a possible asymmetry of the structure, the geometry of grids, and the elastic properties of cement mortar and steel.Riga Technical University, Riga, LV-1047, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 181–186, March–April, 1999.     

Elastic displacements of a cement-based composite beam reinforced with punched steel grids

Using Mohr's method, a procedure is proposed for calculating the elastic displacements of a cement-based composite beam reinforced with punched steel grid ribbons. The approach proposed takes into account a possible asymmetry of the structure, the geometry of grids, and the elastic properties of cement mortar and steel.