Installation Error in Determining the Longitudinal Elasticity Modulus of Unidirectional Fiberglass

The purpose of the work is to estimate the effect of installation error in the form of eccentricity of the working area and grip zone on the measured value of the longitudinal elasticity modulus under tension of rods made of unidirectional fiberglass. The research methodology included the development of a calculation scheme and analysis of the stress-strain state of a statically indeterminate rod subjected to axial tension. The radial displacement of the end of the rod with rigidly clamped edges is equal to the installation eccentricity of the working part relative to the grip zone. Additional axial deformations of the rod are determined by the energy method using the Mohr integral. The effect of the transverse force on the longitudinal deformations of the rod was neglected due to its smallness. An analytical dependence was obtained for determining longitudinal deformations caused by the influence of the bending moment from an eccentrically applied tensile force. The calculation assessment of additional deformations was carried out using the example of rods with a circular cross-section and strips of rectangular cross-section, made of unidirectional fiberglass with deformation properties identical to those of fiberglass reinforcement with a nominal diameter of 6 mm, manufactured in accordance with СТБ [STB – Standards of the Republic of Belarus] 1103–98. It is shown that for rods with a ratio of length l to diameter d or thickness h of at least 30, additional longitudinal deformations of the rod, determining the error in measuring the modulus of longitudinal elasticity, do not exceed 1 % in the entire considered range of axial loads. A more noticeable contribution is observed for short rods (l/d = 20) at a level of tensile axial stresses of 200 MPa and less. The research results can be used in engineering practice and in the educational process in the training of specialists in the construction and chemical engineering profile.

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