Assessement of tensile strength of graphites by the Iosipescu coupon test

Abstract

Polycrystalline graphites are widely used in the metallurgical, nuclear and aerospace industries. Graphites are particulated composites manufactured with a mixture of coke with pitch, and changes in relative proportions of these materials cause modifications in their mechanical properties. Uniaxial tension tests must be avoided for mechanical characterization in this kind of brittle material, due to difficulties in making the relatively long specimens and premature damages caused during testing set-up. On other types of tests, e.g. bending tests, the specimens are submitted to combined stress states (normal and transverse shear stresses). The Iosipescu shear test, is performed in a beam with two 90° opposite notches machined at the mid-length of the specimens, by applying two forces couples, so that a pure and uniform shear stress state is generated at the cross section between the two notches. When a material is isotropic and brittle, a failure at 45° in relation to the beam long axis can take place, i.e., the tensile normal stress acts parallel to the lateral surface of the notches, controls the failure and the result of the shear test is numerically equivalent to the tensile strength. This work has evaluated a graphite of the type used in rocket nozzles by the Iosipescu test and the resulted stress, ~11 MPa, was found to be equal to the tensile strength. Thus, the tensile strength can be evaluated just by a single and simple experiment, thus avoiding complicated machining of specimen and testing set-up

Graphite Modified Polylactide (PLA) for 3D Printed (FDM/FFF) Sliding Elements

“…Up to 7.5% graphite for samples conditioned at 40 • C and up to 5% for samples conditioned in a climate oven, fracture stress and fracture strain were virtually unchanged within the levels of standard deviation. For higher loadings, the strain at the breaking of the modified samples was lower than that of the reference sample, which is due to low tensile fracture strain of the graphite itself, which is below 0.5% [43]. Therefore, graphite particles embedded in PLA either undergo fracture before the failure of the sample itself or they have too little adhesion to the matrix and get pulled out of the material during sample straining, failing to serve a role of a reinforcing filler, especially at high loadings.…”

Sticky or not sticky? Measurements of the tensile strength of microgranular organic materials

“…They show similar slopes as paraffin, which has the smallest slope among the used materials in this study. From Manhani et al (2007) an additional data point for graphite was retrieved (open pentagon in Figure 4). They used a highly compacted graphite sample with a median grain size of 838 µm whose volume filling factor was around 0.77 and measured a tensile strength of 11.7 MPa.…”

“…Compared with literature values, the specific surface energy of graphite AF matches pretty well the results of earlier studies (the values range between 0.063 ± 0.007 J/m 2 (Ferguson et al 2016) and 0.260 ± 0.029 J/m 2 (Girifalco & Lad 1956), see also Han et al 2019). However, as mentioned before, Manhani et al (2007) measured the tensile strength of a compact graphite sample whose volume filling factor is about 0.77. Their result of a tensile strength of 11.7 MPa falls in the regime we would expect, but due to the different grain size with a median of 838 µm, we cannot extrapolate our data to it.…”

Impact experiments of exotic dust grain capture by highly porous primitive bodies

“…4 shows the relationshi p between the MW/PD ratio and the initial dynamic pressure, normalized by the projectile's tensile strength. We also plotted the results of various projectile s into aerogel, as obtained in previous studies (Burchell et al, 2008;Hörz et al, 2009;Kearsley et al, 2012;Niimi et al, 2012), using the tensile strength of soda-lime glass, copper (60 MPa, 195 MPa, respectively;Kaye and Laby, 1986 ), alumina (258 MPa;Shackelford and Alexander , 2000 ), carbonaceous chondrite meteorit es (637, 614, 614 MPa for Allende, Murchison, Orgueil, respectively ; Tsuchiya ma et al, private communicati on, 2012), and graphite (10.9 MPa; Manhani et al, 2007 ). The MW/ PD ratio increases with increasing dynamic pressure.…”