Effect of stability of the structural parameters of laminated reinforced plastics on their strength properties
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As a result of the completed analysis, we estimated the effect of scatter of the strength properties of the layers, instability of the layers' strain properties, and instability of the geometry of the structure on the strength properties of multidirectional LRP's in a plane stress state. It was established that instability of the structural parameters produces two negative tendencies: a reduction in the mean values of LRP strength and an increase in their scatter. From the viewpoint of ensuring the reliability of structures (structural elements) made of such materials, these tendencies reinforce one another and are thus even more dangerous. It follows from this that the production method employed should not only (or not even mainly) solve the problem of increasing the values of the parameters of the materials (and their semifinished structural elements), it should also address the problem of alleviating their instability — improving the “quality of production.”
The numerical analysis established the limits at which it is necessary to account for instability of structural parameters in engineering calculations: for the strain properties of the layers — a coefficient of variation of the elastic modulus greater than 10%; for the scatter of the angles of orientation of the layers — a standard deviation greater than 5 °. These numerical results and the computer program developed may prove useful in evaluating the actual properties of structural parameters determined in indirect tests of LRP's, as well as in more adequately comparing empirical data with corresponding calculations based on structural theories. The development of such an approach to analyzing the strength properties of multidirectional LRP's in bending also holds promise.
KeywordsStandard Deviation Stress State Elastic Modulus Computer Program Empirical Data
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- 1.M. R. Gurvich and A. M. Skudra, “Effect of the geometry of the structure on the distribution of multilaminate three-directional reinforced plastics,” Mekh. Kompozitn. Mater., No.5, 805–812 (1988).Google Scholar
- 2.M. R. Gurvich, “Evaluating the reliability of reinforced plastics in a plane stress state,” in: Mechanics of Composite Materials [in Russian], Riga (1988), pp. 110–120.Google Scholar
- 3.I. M. Sobol', Monte Carlo Numerical Methods, Moscow (1973).Google Scholar
- 4.S. E. Yamada and C. T. Sun, “Analysis of laminate strength and its distribution,” J. Compos. Mater.,12, No. 3, 275–284 (1978).Google Scholar
- 5.V. D. Protasov, A. F. Ermolenko, A. A. Filipenko, and I. P. Dimitrienko, “Study of the load-carrying capacity of complex cylindrical shells by computer modeling of the fracture process,” Mekh. Kompozitn. Mater., No. 2, 254–261 (1980).Google Scholar
- 6.M. Yemura and H. Fukunara, “Probabilistic burst strength of filament-wound cylinders under internal pressure,” Carbon Reinforced Epoxy Systems. Pt. IV, Materials Technology Series, Vol. 12, 102–119 (1984).Google Scholar
- 7.M. R. Gurvich, “Effect of thickness on the strength distribution of laminated reinforced plastics,” in: Mechanics of Composite Materials [in Russian], Riga (1988), pp. 121–128.Google Scholar