Tensile Fracture Strength Research Articles

Effect of repeated compaction of tablets on tablet properties and work of compaction using an instrumented laboratory tablet press

The repeated compaction of Avicel PH101, dicalcium phosphate dihydrate (DCP) powder, 50:50 DCP/Avicel PH101 and Starch 1500 was studied using an instrumented laboratory tablet press which measures upper punch force, punch displacement and ejection force and operates using a V-shaped compression profile. The measurement of work compaction was demonstrated, and the test materials were ranked in order of compaction behaviour Avicel PH101 > DCP/Avicel PH101 > Starch > DCP. The behaviour of the DCP/Avicel PH101 mixture was distinctly non-linear compared with the pure components. Repeated compaction and precompression had no effect on the tensile fracture strength of Avicel PH101 tablets, although small effects on friability and disintegration time were seen. Repeated compaction and precompression reduced the tensile strength and the increased disintegration time of the DCP tablets, but improved the strength and friability of Starch 1500 tablets. Based on the data reported, routine laboratory measurement of tablet work of compaction may have potential as a critical quality attribute of a powder blend for compression. The instrumented press was suitable for student use with minimal supervisor input.

Interactions Affecting the Mechanical Properties of Macromolecular Microsphere Composite Hydrogels

Macromolecular microsphere composite (MMC) hydrogel is a kind of tough hydrogel fabricated by using peroxidized macromolecular microspheres as polyfunctional initiating and cross-linking centers (PFICC). The contribution of chemical cross-linking (covalent bonding) and physical cross-linking (chain entanglement and hydrogen bonding) to the mechanical properties are understood by testing the hydrogels, which were swollen in water or aqueous urea solutions to different water contents. The as-prepared MMC gels exhibited moderate moduli (60-270 kPa), high fracture tensile stresses (up to 0.54 MPa), high extensibilities (up to 2500%), and high fracture energies (270-770 J m(-2)). The moduli of the swollen gels decrease dramatically, but there are no significant changes in fracture tensile strength and fracture strain, even slight increases. More interestingly, the swollen gels show much-enhanced fracture energies, higher than 2000 J m(-2). A gradual decrease in the hysteresis ratio and residual strain is also found in the cyclic tensile testing of the hydrogels that were swollen to different water contents. The covalent bonding determines the tensile strength and fracture energy of the MMC gels, whereas the physical entanglement and hydrogen bonding among the polymer chains contributes mainly to the modulus of the MMC gels, and they are also the main reason for the presence of hysteresis in the loading-unloading cycles.

Tensile Fracture Strength of Brisbane Tuff by Static and Cyclic Loading Tests

This research presents the results of laboratory experiments during the investigation of tensile strength–strain characteristics of Brisbane tuff disc specimens under static and diametral cyclic loading. Three different cyclic loading methods were used; namely, sinusoidal cyclic loading, type I and II increasing cyclic loading with various amplitude values. The first method applied the stress amplitude−cycle number (s–n) curve approach to the measurement of the indirect tensile strength (ITS) and fracture toughness (K IC) values of rocks for the first time in the literature. The type I and II methods investigated the effect of increasing cyclic loading on the ITS and K IC of rocks. For Brisbane tuff, the reduction in ITS was found to be 30 % under sinusoidal loading, whereas type I and II increasing cyclic loading caused a maximum reduction in ITS of 36 %. The maximum reduction of the static K IC of 46 % was obtained for the highest amplitude type I cyclic loading tested. For sinusoidal cyclic loading, a maximum reduction of the static K IC of 30 % was obtained. A continuous irreversible accumulation of damage was observed in dynamic cyclic tests conducted at different amplitudes and mean stress levels. Scanning electron microscope images showed that fatigue damage in Brisbane tuff is strongly influenced by the failure of the matrix because of both inter-granular fracturing and trans-granular fracturing. The main characteristic was grain breakage under cyclic loading, which probably starts at points of contact between grains and is accompanied by the production of very small fragments, probably due to frictional sliding within the weak matrix.

Thermoelectric and mechanical properties of melt spun and spark plasma sintered n-type Yb- and Ba-filled skutterudites

• N-type double filled skutterudites can be formed by a combination of melt spinning and spark plasma sintering, obviating annealing steps. • The consolidated billets have thermoelectric properties that are comparable to those produced using more time and energy intensive powder metallurgical methods. • We demonstrate that the here described preparation route is scalable to 80 g billets as evidenced by the comparable nature of the transport properties of specimens cuts from large samples to those of smaller lab-scale specimens. Here we present thermoelectric and mechanical properties of n-type filled-skutterudites produced by a combination of melt spinning of pre-melted charges with subsequent consolidation by spark plasma sintering, a process we refer to as MS-SPS. This combination of processing steps leads to phase-pure n-type filled-skutterudites and obviates more energy and time intensive annealing steps. We show that both the thermoelectric properties and the tensile fracture strength compare favorably to materials made by traditional methods. The process is scalable to at least 80 g billets, such that the transport properties measured on test bars harvested from these larger billets compare favorably to those measured on lab-scale billets (5 g total billet mass). ZT values approaching 1.1 at 750 K were observed in materials made by MS-SPS. In addition, the tensile fracture strength of test bars cut from an 80 g billet is ∼128 MPa at room temperature and decreases with increasing temperature. Fractography of the test bars reveals that the majority failed due to surface and edge flaws with few failures due to volume type flaws. This indicates that the powder metallurgical methods employed to produce these samples is mature.

Adhesion enhancement of Al coatings on carbon/epoxy composite surfaces by atmospheric plasma

Adhesion strengths between aluminium thin film coatings and manufactured carbon/epoxy composite surfaces were measured by assessing fracture tensile strengths using pull-off tests. The effect of the substrate roughness (nm to μm) of these composite surfaces on adhesion was studied by examining the surface free energies and adhesion strengths. The adhesion strengths of the coatings varied significantly. To improve the coating adhesion, each composite surface was treated with atmospheric plasma prior to deposition, which resulted in an increase in the surface free energy from approximately 40mJ/m2 to 70mJ/m2 because the plasma pretreatment led to the formation of hydrophilic CO and CO bonds on the composite surfaces, as demonstrated by X-ray photoelectron spectroscopy analyses. The adhesion strengths of the coatings were enhanced for all surface roughnesses studied. In our study, the effect of mechanical adhesion due to roughness was separated from the effect of modifying the chemical bonds with plasma activation. The adhesion ability of the pure resin was relatively weak. Increasing the surface roughness largely improved the adhesion of the resin surface. Plasma treatment of the pure resin also increased the surface adhesion. Our study shows that plasma activation effectively enhances the adhesion of manufactured composites, even when the surface roughness is on the order of microns. The ageing of the surface activation was also investigated, and the results demonstrate that atmospheric plasma has potential for use in the pretreatment of composite materials.

Comparison of the Characteristics of LDPE : PP and HDPE : PP Polymer Blends

Comparative studies have been made on the mechanical properties of High density polyethylene/polypropylene (HDPE : PP) and Low density polyethylene/polypropylene (LDPE : PP) binary blends. Morphological analysis has been also performed using SEM. Blends have been prepared by melt mixing in an extruder. Mechanical tests were performed on the two groups of binary blends. Binary blends (HDPE : PP) gave higher values of tensile strength, fracture strength, young modulus, hardness, creep rate and creep modulus than LDPE : PP. The blend of ratio 20%HDPE : 80%PP shows superior mechanical properties, this blend could bear a load of 846.9 N with an extension of 3.94 mm. SEM results indicated that 20HDPE : 80PP and 20LDPE : 80PP are immiscible blends.

Controlled cavitation to augment SWL stone comminution: mechanistic insights in vitro

Stone comminution in shock wave lithotripsy (SWL) has been documented to result from mechanical stresses conferred directly to the stone, as well as the activity of cavitational microbubbles. Studies have demonstrated that the presence of this cavitation activity is crucial for stone subdivision; however, its exact role in the comminution process remains somewhat weakly defined, in part because it is difficult to isolate the cavitational component from the shock waves themselves. In this study, we further explored the importance of cavitation in SWL stone comminution through the use of histotripsy ultrasound therapy. Histotripsy was used to target model stones designed to mimic the mid-range tensile fracture strength of naturally occurring cystine calculi with controlled cavitation at strategic time points in the SWL comminution process. All SWL was applied at a peak positive pressure (p+) of 34 MPa and a peak negative pressure (p-) of 8 MPa; a shock rate of 1 Hz was used. Histotripsy pulses had a p- of 33 MPa and were applied at a pulse repetition frequency (PRF) of 100 Hz. Ten model stones were sonicated in vitro with each of five different treatment schemes: A) 10 min of SWL (600 shocks) with 0.7 s of histotripsy interleaved between successive shocks (totaling to 42 000 pulses); B) 10 min of SWL (600 shocks) followed by 10 min of histotripsy applied in 0.7-s bursts (1 burst per second, totaling to 42 000 pulses); C) 10 min of histotripsy applied in 0.7-s bursts (42 000 pulses) followed by 10 min of SWL (600 shocks); D) 10 min of SWL only (600 shocks); E) 10 min of histotripsy only, applied in 0.7-s bursts (42 000 pulses). Following sonication, debris was collected and sieved through 8-, 6-, 4-, and 2-mm filters. It was found that scheme D, SWL only, generated a broad range of fragment sizes, with an average of 14.9 ± 24.1% of the original stone mass remaining > 8 mm. Scheme E, histotripsy only, eroded the surface of stones to tiny particulate debris that was small enough to pass through the finest filter used in this study (<2 mm), leaving behind a single primary stone piece (>8 mm) with mass 85.1 ± 1.6% of the original following truncated sonication. The combination of SWL and histotripsy (schemes A, B, and C) resulted in a shift in the size distribution toward smaller fragments and complete elimination of debris > 8 mm. When histotripsy-controlled cavitation was applied following SWL (B), the increase in exposed stone surface area afforded by shock wave stone subdivision led to enhanced cavitation erosion. When histotripsy-controlled cavitation was applied before SWL (C), it is likely that stone surface defects induced by cavitation erosion provided sites for crack nucleation and accelerated shock wave stone subdivision. Both of these effects are likely at play in the interleaved therapy (A), although shielding of shock waves by remnant histotripsy microbubble nuclei may have limited the efficacy of this scheme. Nevertheless, these results demonstrate the important role played by cavitation in the stone comminution process, and suggest that the application of controlled cavitation at strategic time points can provide an adjunct to traditional SWL therapy.

Nonlinear tensile deformation behavior of melt-extracted Co69.5Fe4.5Cr1Si8B17 amorphous wires

Metallic glasses often show excellent mechanical and physical properties due to their random atomic packing. But as a new kind of potential engineering material, metallic glasses have challenged the traditional processing methods. In this letter, continuous Co69.5Fe4.5Cr1Si8B17 metallic glassy wires at micrometer scales with a smooth surface and negligible fluctuation in diameter were prepared by the melt-extraction method. Their mechanical properties were evaluated by carrying out tensile tests. The Co69.5Fe4.5Cr1Si8B17 metallic glassy wires show high tensile fracture strength of the order of 2.8GPa and perform nonlinear deformation behavior prior to fracture. The tensile failure of the glassy wires was controlled by both the normal stress and shear stress.

Mechanical and thermo‐physical properties of high‐density polyethylene modified with talc

AbstractThe aim of this study was to examine the physical, mechanical, and thermo‐physical properties of high‐density polyethylene (HDPE) modified with talc. Different weight fractions of talc (up to 35 wt %) were compounded with an HDPE matrix containing 2.5 wt % of carbon black (CB) in a twin‐screw compounder. The composites were then processed by injection moulding to obtain specimens for testing. The results indicate that CB causes a significant decrease in the toughness, while talc not only enhances the thermal conductivity and thermo‐physical properties of the composites but can also play a role in compensating for the negative effects of CB on impact resistance. The experimental data show that the presence of CB reduces the impact resistance of HDPE by up to 34%, while addition of up to 8 wt % talc can return this value to close to that of pure HDPE. No significant effect on the composite tensile yield and fracture strength was observed for either component at all concentrations. The thermal conductivity, thermal diffusivity, and specific density values of the composites increased almost linearly, but the increase in moisture absorption in the long term showed nonlinear behavior in the concentration range of the experiment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

동적하중 하에서 석회암의 변형 및 파괴거동에 관한 실험적 연구

Information on the deformation behavior and fracture strength of rocks subjected to dynamic loadings is important to stability analyses of underground openings underground vibration due to rock blasts, earthquakes and rock bursts. In this study, Split Hopkinson Pressure Bar (SHPB) system was applied to estimate dynamic compressive and tensile fracture strengths of limestone and also examine deformation behavior of limestones under dynamic loadings. A micro-focus X-ray CT scanner was used to observe non-destructively inside the impacted limestone specimens. From the dynamic tests, it was revealed that the limestone have over 140MPa dynamic compressive strength and the strain-rate dependency of the strength. Dynamic Brazilian tensile strength of the limestone exceeds 21MPa and shows over 3 times static Brazilian tensile strength.

Investigation of Structure and Properties of PET Multifilament Irradiated with UV in Different Atmosphere

Changes of mechanical properties and chemical structure of polyester (PET) fibers are studied through UV simulated accelerated ageing experiments with N2, air and O3 as the atmosphere. The structure, thermal stabilities and tensile strength are obtained by FTIR, DTA-TG, XRD, SEM and micro-mechanics test. The difference of degradation process in various atmospheres is discussed in this paper. The results show that the fracture tensile strength of PET multifilament decreases with the increase of UV irradiation time. And oxidation and then decarbonylation take place on the surface. Besides, Melting temperature (Tm), the temperature of quality loss by 10% (T10) and the crystallization also decrease. However, in O3 atmosphere the oxidation develops very quickly and fully, therefore, the carbonyl on the surface is eliminated and decreases significantly, and the tensile strength decreases much faster than those in N2 and air. The skin layer of irradiated fibers appears serious damaged. The mechanism of chemical degradation for samples irradiated in N2 environments is similar to those irradiated in air.

Tensile failure of two-dimensional quasi-brittle foams

Stress redistribution caused by damage onset and the subsequent local softening plays an important role in determining the ultimate tensile strength of a cellular structure. The formation of damage process zones with struts dissipating a finite amount of fracture energy will require the macroscopic stress to be increased in order to continue structural damage. The goal of this paper is to investigate the influence of the fracture energy of the solid on the tensile fracture strength and the strain to fracture in quasi-brittle two-dimensional foams using a microstructural model. We analyze the mesoscopic damage and failure mechanisms in uniaxial tension. Relative density, strut cross-sectional profile, solid’s fracture strain, and fracture energy are varied systematically. The effect of the specific fracture energy on the peak behavior has been shown to be captured by the ratio of the fracture energy to the stored elastic energy. We have also explored the net section strength variation in the presence of a central crack at two different fracture energies. Comparison is made between two structurally identical quasi-brittle and ductile strain hardening foams to identify the differences in the damage mechanisms.

Dependence of tensile fracture strength of high-density wet snow on density and liquid-water content

Dependence of tensile fracture strength of high-density wet snow on density and liquid-water content

Use of spherical indentation technique for measurement of property variations of γTiAl

Abstract

Tensile properties of high strength polyacrylonitrile (PAN)-based and high modulus pitch-based hybrid carbon fibers-reinforced epoxy matrix composite

The tensile properties of high strength polyacrylonitrile-based (IM600) and high modulus pitch-based (K13D) hybrid carbon fibers-reinforced epoxy matrix composite (CFRP) were investigated. Fiber orientation of the hybrid CFRP specimen was set to [0(IM600)/0(K13D)]2S. The fiber volume fraction of the hybrid CFRP specimen was 55.7 vol% (IM600: 29.3 vol%, K13D: 26.4 vol%). The tensile stress–strain curve of the hybrid CFRP specimen shows a complicated shape (jagged trace). By the high modulus K13D CFRP layers, the hybrid CFRP specimen shows the intermediate modulus in the initial stage of loading. Subsequently, when the K13D CFRP layers begin to fail, the high strength IM600 CFRP layers would hold the load (strength) and the material continues to endure high load without instantaneous failure. Because higher strength fiber can help the load for a certain time after failure occur, the hybrid composite could be considered one example of a material possessing preventing instantaneous failure. The Weibull statistical distributions of the mono (IM600 and K13D) and the hybrid CFRP specimens were also examined. The Weibull modulus for the mono CFRP specimens was calculated to be 22.9 for the IM600 CFRP specimen and 14.4 for the K13D CFRP specimen, respectively. The Weibull modulus for the hybrid CFRP specimen was calculated to be 39.6 for the initial fracture strength and 20.6 for the tensile fracture strength, respectively. The Weibull modulus for the initial fracture strength is higher than that for the K13D CFRP specimen and the Weibull modulus for the tensile fracture strength is almost similar to that for the IM600 CFRP specimen.

Effect of curing temperature on properties and solvent welding strength of ovalbumin

AbstractEffect of curing temperature on properties of ovalbumin has been investigated. Functional basis, crosslinking degree, tensile strength, and hardness increases with rising curing temperature. The increase of visible transmittance and the decrease of absorption accompany with increasing wavelength. The absorptive peak shows at 440–450 nm and the wavelength of the absorptive peak increases with the rising curing temperature. The relationship of joint strength with solvent welded joints of ovalbumin to their microstructure is also investigated. Ovalbumin can promote joint strength after the treatment of distilled water and curing. Comparing joint strength with fracture morphology, the smoother fracture surface morphology is related to the maximum tensile and shear joint strength, respectively. The joint strength is increasing with curing temperature and compressive stress, and the joint strength of treatment with 150°C curing temperature and 0.12 kgf/mm2 compressive stresses are larger than its original tensile fracture strength of cured ovalbumin at same curing temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Mechanical Properties of Bamboo-like Boron Nitride Nanotubes by In Situ TEM and MD Simulations: Strengthening Effect of Interlocked Joint Interfaces

Understanding the influence of interfacial structures on the nanoarchitecture mechanical properties is of particular importance for its mechanical applications. Due to a small size of constituting nanostructural units and a consequently high volume ratio of such interfacial regions, this question becomes crucial for the overall mechanical performance. Boron nitride bamboo-like nanotubes, called hereafter boron nitride nanobamboos (BNNBs), are composed of short BN nanotubular segments with specific interfaces at the bamboo-shaped joints. In this work, the mechanical properties of such structures are investigated by using direct in situ transmission electron microscopy tensile tests and molecular dynamics simulations. The mechanical properties and deformation behaviors are correlated with the interfacial structure under atomic resolution, and a geometry strengthening effect is clearly demonstrated. Due to the interlocked joint interfacial structures and compressive interfacial stresses, the deformation mechanism is switched from an interplanar sliding mode to an in-plane tensile elongation mode. As a result of such a specific geometry strengthening effect, the BNNBs show high tensile fracture strength and Young's modulus up to 8.0 and 225 GPa, respectively.

Tensile deformation and failure of North American porcupine quills

Although the mechanical properties of some keratin-based biological materials have been extensively studied (i.e., wool) and others are beginning to be studied (e.g., horn, hooves and avian quills), data on the properties of porcupine quill are less common. Porcupine quill is a keratin-based biological material composed of a cylindrical outer shell with an inner foam core. The present paper reports on the physical characteristics, tensile properties and fracture behavior of North American porcupine quills conditioned at relative humidities of 65% and 100%. Increasing the water content decreased the tensile stiffness and strength and increased the strain at fracture of the porcupine quills. The tensile fracture strength of porcupine quill was found to be 146 MPa at 65% RH and 60 MPa at 100% RH. Although these values compare favorably with reported values for African porcupine quill, reported values of the tensile strengths of wool with similar moisture contents are considerably higher. The initial moduli of porcupine quill (2700 MPa at 65% RH and 1000 MPa at 100% RH) compare favorably to those reported for wool but are considerably less than previous reports for African porcupine quill. The engineering strains at fracture were measured as 25% at 65% RH and 49% at 100% RH and these values are also comparable to other keratin-based mammalian materials. Scanning electron microscopy of the fracture surfaces of porcupine quills revealed that the cylindrical outer shells of quills are composed of 2–3 layers with distinctly different fracture characteristics, especially when the samples contain 100% RH. The outer layer of the porcupine quill shell appears to resist the plasticizing effects of moisture and appears to exhibit considerably less ductility than the inner layers, perhaps due to the presence of hydrophobic lipids in the outer layer.

Temperature Dependent Tensile Fracture Stress of &lt;I&gt;n&lt;/I&gt;- and &lt;I&gt;p&lt;/I&gt;-Type Filled-Skutterudite Materials

While materials with excellent thermoelectric performance are most desirable for higher heat to electrical energy conversion efficiency, thermoelectric materials must also be sufficiently mechanically robust to withstand the large number of thermal cycles and vibrational stresses likely to be encountered while in service, particularly in automotive applications. Further these TE materials should be composed of non-toxic and naturally abundant constituent elements and be available as both n- and p-type varieties. Skutterudite based thermoelectric materials seemingly fit this list of criteria. In this contribution we report on the synthesis, tensile fracture strengths, low temperature electrical and thermal transport properties, and coefficients of thermal expansion (CTE), of the n-type skutterudite La{sub 0.05({+-}0.01)}Ba{sub 0.07({+-}0.04)}Yb{sub 0.08({+-}0.02)}Co{sub 4.00({+-}0.01)}Sb{sub 12.02({+-}0.03)} and the p-type Ce{sub 0.30({+-}0.02)}Co{sub 2.57({+-}0.02)}Fe{sub 1.43({+-}0.02)}Sb{sub 11.98({+-}0.03)}. Both materials have tensile fracture strengths that are temperature independent up to 500 C, and are in the range of {approx}140 MPa as measured by a three point bend flexure test fixture described herein. The CTE's were measured by dual rod dilatometry and were determined to be 10.3 ppm/C for the n-type material and 11.5 ppm/C for p-type up to 450 C.

Weibull analysis of fracture strength for Zr55Ti2Co28Al15bulk metallic glass: Tension–compression asymmetry and porosity effect

Abstract