![]() ![]() Moreover, because of the stress gap between yielding (upsetting) stress and the fracture stress (tensile or compressive strength), at the the frature time point there is 2 certain layers (of course thinner than the half-height of the sample, located at the upper side and lower side the the section of the sample), and upper side layer has been yielded by compression, and lower side layer by tension, the left layer (sentral layer besides the central line) is still in elastic mode. stress 0 is at just the central line (plane), -Xmax at the upper surface of the sample. The flexural loading distributes in the sample at the summit section in a particular mode, say, below the central plane (line) it is a linear tension stress from 0 to Xmax (as you calculated as the fletural strength), and in the upper side of the section, it is a compression stress field: from -Xmax to 0. The relationship is really exist for an isotropic and homogeneous material, but both the plastic and elastic property might be absolutely same. Good luck to you on your way from unknowledge to the knowledge.! Maybe, Coulomb's (shear) modulus.? And it is too long story about the elastic characteristics of graphene containing materials, but the main idea you need to understand clearly in this case that these characteristics depend on the volume fraction of graphite/graphene inclusions extremely sharply. I don't know what you have termed as "flexural modulus". This is the specifity of all the transversely isotropic materials. However, be sure that the characteristics are different for two main directions. The full-text of the chapter is available on my account in the ResearchGate. You can find there the ratios between tensile, flexural and compressive strength characteristics as well, but also many other useful, in my opinion, things for your present and future studies. Concerning the similar materials I can refer you to Chapter 2 of the 1st Volume of my book on the UHTM (recently published). I am researching graphite/graphene containing materials for more than 40 years so, I can predict with the high degree of probability that your so-called "epoxy resin which is reinforced with graphene nano platelets" is a transversely isotropic material. All the real materials are anisotropic (!), if only you are doing your measurements properly and thoroughly. Hence the strength in two modes of testing may differ.Īn isotropic material (similar to ideal gas!) does not exist in the nature. A defect nearer top or bottom surface will have significant effect as compared to the same type of defect located nearer or on the neutral axis. In bending situation however defects will affect the strength differently depending upon their location. Only difference is if any defect is present in the specimen irrespective of its location it affects tensile strength in the same manner because uifom tensile stresses are produced across the whole cross section. In fact for ceramic materials tensile strength is obtained using 3 point bending set-up because tensile specimens for ceramic materials cannot be prepared. Hence when tested using tensile mode on a UTM we designate it as tensile strength and when tested on flexural loading set-up, we call it as flexural strength. Since the isotropic material fails in tensile portion the strength is nothing but its tensile strength. In isotropic materials, when the material fails, the corresponding load is taken for calculation of flexural strength. under bending tensile stresses are produced on the top layers zero stress at neutral axis and compressive stresses in layers below the neutral axis. When a material is tested in flexure, i.e. ![]()
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