A new test method for measuring the longitudinal and shear moduli of fiber-reinforced composites.
Date
1998
Authors
Jalali Mosallam, Seyed Javad.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
The longitudinal and the shear moduli of fiber-reinforced plastic composites (FRPC) are commonly measured by separate test methods. This thesis introduces a new test method which enables one to measure these properties simultaneously. In the new test method, specimens with different span-to-depth ratios (L/h) are subjected to three-point bending. The method will be called the "Varying-Span Method" (VSM), since for a given material producing different L/h is simply achieved by changing the test span.
One of the common methods for evaluating the longitudinal modulus of FRPC is to conduct flexural tests on rectangular specimens. The longitudinal modulus is determined by a simple equation which is based on the Euler beam theory. Since this theory does not account for the shear deformation, the evaluated modulus is usually underestimated. The effect of shear deformation reduces when L/h of the specimen increases. However, since in general FRPC have low shear modulus, to eliminate the shear deformation effect from the evaluated modulus, one must use specimens with large span to depth ratios (say $L/h>$60, see for example, Zweben et. al. 1979). In the VSM, instead of eliminating the effect of the shear deformation from the result of the flexural test, the attribute is used to simultaneously evaluate both the longitudinal and the shear moduli of the material. In this method, the test is considered as a phenomenon with two unknowns, namely, the longitudinal and the shear moduli. Theoretically, these unknowns can be obtained by conducting at least two tests on specimens with different L/h.
Among the advantages of the VSM is its capability of measuring the through-the-thickness shear modulus of specimens with relatively small thickness (say 2 mm). For this, a special apparatus was designed and fabricated. The apparatus was used for the evaluation of the longitudinal and shear moduli of composites made of graphite/epoxy, Kevlar/epoxy and E-glass/epoxy. The results and their comparison with the values obtained by other common test methods are presented.
A review of the most popular methods for the measurement of the longitudinal and the shear moduli of FRPC is presented in this manuscript. The advantages and the disadvantages of each method are discussed. The exact elasticity solution of a beam subjected to three-point bending is developed. This solution is used as a means to assess the integrity of the VSM. The relevant theories with respect to the VSM are reviewed. The application of these theories is discussed and a solution which accounts for the local effect of the concentrated load and the reaction forces on the deformation of the beam is presented. Factors that influence the accuracy and efficiency of the proposed method are identified and investigated. The integrity of the method is examined and proved by theoretical and experimental investigations.
Thesis (Ph.D.)--DalTech - Dalhousie University (Canada), 1998.
One of the common methods for evaluating the longitudinal modulus of FRPC is to conduct flexural tests on rectangular specimens. The longitudinal modulus is determined by a simple equation which is based on the Euler beam theory. Since this theory does not account for the shear deformation, the evaluated modulus is usually underestimated. The effect of shear deformation reduces when L/h of the specimen increases. However, since in general FRPC have low shear modulus, to eliminate the shear deformation effect from the evaluated modulus, one must use specimens with large span to depth ratios (say $L/h>$60, see for example, Zweben et. al. 1979). In the VSM, instead of eliminating the effect of the shear deformation from the result of the flexural test, the attribute is used to simultaneously evaluate both the longitudinal and the shear moduli of the material. In this method, the test is considered as a phenomenon with two unknowns, namely, the longitudinal and the shear moduli. Theoretically, these unknowns can be obtained by conducting at least two tests on specimens with different L/h.
Among the advantages of the VSM is its capability of measuring the through-the-thickness shear modulus of specimens with relatively small thickness (say 2 mm). For this, a special apparatus was designed and fabricated. The apparatus was used for the evaluation of the longitudinal and shear moduli of composites made of graphite/epoxy, Kevlar/epoxy and E-glass/epoxy. The results and their comparison with the values obtained by other common test methods are presented.
A review of the most popular methods for the measurement of the longitudinal and the shear moduli of FRPC is presented in this manuscript. The advantages and the disadvantages of each method are discussed. The exact elasticity solution of a beam subjected to three-point bending is developed. This solution is used as a means to assess the integrity of the VSM. The relevant theories with respect to the VSM are reviewed. The application of these theories is discussed and a solution which accounts for the local effect of the concentrated load and the reaction forces on the deformation of the beam is presented. Factors that influence the accuracy and efficiency of the proposed method are identified and investigated. The integrity of the method is examined and proved by theoretical and experimental investigations.
Thesis (Ph.D.)--DalTech - Dalhousie University (Canada), 1998.
Keywords
Engineering, Civil.