Axial Tensile Modulus Research Articles

Tensile properties and morphological insights into chemically modified fibres of Pseudoxytenanthera bamboo species as sustainable reinforcements in composites

This study evaluated the tensile properties of fibres from Pseudoxytenanthera ritcheyi and P. stocksii, with reference to the more commonly used Bambusa balcooa, in order to determine their viability as reinforcements in structural composite materials. Tensile tests were conducted on individual fibres under three distinct moisture conditions: ambient conditions, desiccated (fully dry) conditions, and saturated conditions for both untreated and chemically treated fibres. The investigation focused on comparing the axial tensile modulus and ultimate strength of bamboo fibres with varying gauge lengths. Notably, fracture morphology analysis using scanning electron microscopy (SEM) allowed a comprehensive correlation between natural fibre characteristics and their mechanical properties. A water absorption study was also conducted on these fibres. Additionally, thermogravimetric analysis was performed to assess the thermal stability of the fibres. The results indicate that Pseudoxytenanthera species exhibit promising potential for the development of high-performance, sustainable materials within the realm of composite materials. This research contributes to expanding the understanding of bamboo fibres and their suitability as reinforcements in structural composites, thus promoting advances in the field of composite material engineering.

Mechanical reliability of extruded PLA filaments

The mechanical characteristics of 3D printed polymer materials such as strength and stiffness depends on extruded filaments, which are fundamental building blocks. Currently there is a lack of studies on the effects of length scaling on the strength and reliability of extruded filaments. In this study, single extruded filaments (SEF), multiple extruded filaments without overlap (MEFWNO) and multiple extruded filaments with overlap (MEFWO) of Polylactic acid (PLA) material with different gauge lengths (5, 10 and 15 cm) are tested for axial tensile modulus, ultimate strength, failure strain and toughness. A probabilistic strength prediction model of individual extruded filaments, as well as extruded filaments with and without overlap is developed, wherein the 2-parameter Weibull distribution is used to determine the probability of failure of extruded filaments at various stresses. Reliability curves for tensile stress to failure and tensile strain to failure are developed for SEF, MEFWNO and MEFWO. Higher tensile strength, Young modulus, strain at failure and toughness are demonstrated for MEFWO compared to MEFWNO, enabling quantification of the effect of overlap between two adjacent extruded filaments. This data can further be used for analytical and numerical material constitutive modeling of 3D printed PLA with various deposition orientations and layups in components.

Axial Tensile Testing of Single Fibres

The mechanical and damage properties of single fibres used in fibrous composite have gained tremendous importance in recent years. These properties are used in determination of effective properties of composites by micromechanics. These are also used in the micromechanical damage modeling. Further, these properties are used as an indicator of the excellence of product by manufacturers. In the present study the axial tensile modulus, ultimate strength and failure strain of single fibres are determined for carbon and glass fibres. ASTM D3379-75 standard is followed and a number of fibers are tested for statistical analysis. The axial tensile moduli measured are 246.7 GPa and 93.3 GPa, respectively and strength are 3031.6 MPa and 2035.9 MPa, respectively for carbon and glass fibres. Further, the respective axial tensile failure strains are 0.0137 and 0.0224. The error in the measurement of axial modulus is below 8% while for axial tensile strength is below 1%.

The tensile properties of electrospun nylon 6 single nanofibers

AbstractIn this article, we have aimed to mechanically characterize the nylon 6 single nanofiber and nanofiber mats. We have started by providing a critical review of the developed mechanical characterization testing methods of single nanofiber. It has been found that the tensile test method provides information about the mechanical properties of the nanofiber such as tensile strength, elastic modulus and strain at break. We have carried out a tensile test for nanofiber/composite MWCNTs nanofiber mats to further characterize the effect of the MWCNTs filling fiber architecture. In addition, we have designed and implemented a novel simple laboratory set‐up for performing tensile test of single nanofibers. As a result, we have established the stress–strain curve for single nylon 6 nanofibers allowing us to define the tensile strength, axial tensile modulus and ultimate strain of this nanofiber. The compared values of the tensile strength, axial modulus and ultimate strain for nylon 6 nanofiber with those of conventional nylon 6 microfiber have indicated that some of the nylon 6 nanofiber molecule chains have not been oriented well along the nanofiber axis during electrospinning and through the alignment mechanism. Finally, we have explained how we can improve the mechanical properties of nylon 6 nanofibers and discussed how to overcome the tensile testing challenges of single nanofibers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1719–1731, 2010

Towards improved understanding of PEG-impregnated waterlogged archaeological wood: A model study on recent oak

Abstract To prevent deformation and cracking of waterlogged archaeological wood, polyethylene glycol (PEG) as a bulk impregnation agent is commonly applied. PEG maintains the wood in a swollen state during drying. However, swelling of wood can reduce its mechanical properties. In this study, the cellular structure of oak and cell wall swelling was characterized by scanning electron microscopy (SEM) of transverse cross-sections, and the microfibril angle of oak fibers was determined by wide angle X-ray scattering (WAXS). Samples of recent European oak (Quercus robur L) impregnated with PEG (molecular weight of 600) were tested in axial tension and radial compression. Mechanical tests showed that axial tensile modulus and strength were only slightly affected by PEG, whereas radial compressive modulus and yield strength were reduced by up to 50%. This behavior can be explained by the microstructure and deformation mechanisms of the material. Microfibril angles in tensile test samples were close to zero. This implies tensile loading of cellulose microfibrils within the fiber cell walls without almost any shear in the adjacent amorphous matrix. These results are important because they can help separate the impact of PEG on mechanical properties from that of chemical degradation in archaeological artifacts, which display only small to moderate biological degradation.

Mechanical characterization of single high-strength electrospun polyimide nanofibres

Ultimate tensile strength and axial tensile modulus of single high-strength electrospun polyimide [poly(p-phenylene biphenyltetracarboximide), BPDA/PPA] nanofibres have been characterized by introducing a novel micro tensile testing method. The polyimide nanofibres with diameters of around 300 nm were produced by annealing their precursor (polyamic acid) nanofibres that were fabricated by the electrospinning technique. Experimental results of the micro tension tests show that polyimide nanofibres had an average ultimate tensile strength of 1.7 ± 0.12 GPa, axial tensile modulus of 76 ± 12 GPa and ultimate strain of ∼3%. The ultimate tensile strength and axial tensile modulus of the electrospun polyimide nanofibres in this study are among the highest ones reported in the literature to date. The precursor nanofibres with similar diameters and molecular weights had an average ultimate tensile strength of 766 ± 41 MPa, axial tensile modulus of 13 ± 0.4 GPa and ultimate strain of ∼43%. The experimental stress–strain curves obtained in this study indicate that under axial tension, the precursor (polyamic acid) nanofibres behave as linearly strain-hardening ductile material without obvious softening at final failure, while the polyimide nanofibres behave simply as brittle material with very high tensile strength and axial tensile modulus. Furthermore, by using a transmission electron microscope, detailed fractographical analysis was performed to examine the tensile failure mechanisms of the polyimide nanofibres, which include chain scission, pull-out, chain bundle breakage, etc. X-ray diffraction analysis of the highly aligned polyimide nanofibres shows the high chain alignment along the nanofibre axis that was formed in the electrospinning process and responsible for the high tensile strength and axial tensile stiffness.

Processing and properties of poly(methyl methacrylate)/carbon nanofiber composites

Single wall carbon nanotubes, multiwall carbon nanotubes, as well as carbon nanofibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nanofibers used was 5 and 10% by weight, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using the small-scale melt processing fiber spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNFs. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. CNF reinforcement efficiency has been analyzed using the modified Cox model.

Novel uses of carbon composites for the fabrication of external fixators

A novel bone fractures external fixator has been developed by using carbon fibre reinforced epoxy resin components. Aim of the project was the design and fabrication of an external fixator lighter than metallic ones, X-rays transparent, with suitable mechanical properties, and sufficiently stable under vapour sterilization conditions. The hydrothermal stability of carbon fibre epoxy resin composites has been assessed by measuring the elastic and ultimate properties of a properly selected carbon fibre-epoxy resin system after prolonged simulated sterilization treatments in water at 120 °C. The suitability of filament winding as a technique appropriate to produce the tubular elements of the designed fixator has been investigated by determining the relationship between winding angle and required mechanical properties of the tubes. Filament wounded composite tubes have been obtained using a high tenacity PAN based carbon fibre and a DGEBA epoxy resin cross-linked by an anhydride based curing agent. Winding angles have been changed in the range from ±5° to 90°. The axial tensile modulus of composite tubes can be reasonably well predicted on the basis of the lamination theory, while the most promising among the analyzed failure criteria in terms of fitting with the experimental axial tensile strength data, seemed to be the Tsai-Wu criterion.

Processing and properties of poly(methyl methacrylate)/carbon nano fiber composites

Single wall carbon nanotubes, multi-wall carbon nanotubes, as well as carbon nano fibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nano fibers used was 5 and 10 wt%, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using small-scale melt spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNF. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. The CNF reinforcement efficiency has been analyzed using the modified Cox model.

Estimation of the axial tensile modulus of a particle-reinforced composite fiber with variable radius

The modulus of a fiber is difficult to measure, especially when the radius of the fiber changes along the length. The use of an arithmetic average radius or volume average radius to calculate fiber modulus leads to an underestimate of the modulus. A model for measuring and calculating the true tensile modulus of a fiber that has large radius variation is proposed. The model has been used to calculate the modulus of a Wollastonite particle-reinforced polypropylene fiber. The difference between the modulus calculated from the model and that from either the arithmetic or volume-average radius increases linearly as the coefficient of variation (CV) of the fiber radius increases, especially when CV< 5%. When the evenness of the fiber increases, i.e. CV → 0, the difference between the three methods for calculating the axial tensile modulus is negligible.

Influence of porosity and fibre coating on engineering elastic moduli of fibre-reinforced ceramics (SiC/SiC)

Porosity generally has a large influence on the modulus of monolithic ceramics. Little, however, is known about its influence in fibre-reinforced ceramics. In the present investigation the influence of porosity on the elastic moduli, i.e. the longitudinal modulus E L , the transverse modulus E T and the longitudinal shear modulus G LT , of unidirectional SiC/SiC ceramic matrix composites is studied. SiC fibres (Nicalon NLM 202) with pyrocarbon coatings of different thicknesses were chemically vapour impregnated by SiC. The axial tensile modulus proved to be little influenced by a porosity content of 13–14%. In fact, the measured modulus was 4–7% smaller than the value predicted with the classical linear rule of mixtures making use of elastic constants of each component and assuming porosity does not reduce the moduli of the different components. On the other hand, the shear and transverse moduli are excessively reduced by the presence of porosity. For a porosity content of 14%, the reduction is roughly 50 and 60% compared with theoretical values for pore insensitive and dense material computed with the model of composite cylinder assemblage and the polarization extremum principle. Finally, the influence of pore morphology on the elastic moduli is discussed.

Tensile and Compressive Properties of Poly(P-Phenylene Benzobisoxazole) Fiber

Axial tensile modulus, compressive modulus and compressive strength of poly(p-phenylene benzobisoxazole) fiber were measured with a Tecam Micro-tensile Testing Machine. This machine was configured to allow direct tension and compression testing of a single fiber at extremely small gauge length. The measured tensile and compressive moduli were analyzed for machine compliance corrections and possible gauge length error. Results were discussed for the effects of non-uniform stress distribution and fiber misalignment. By comparing the axial compressive strengths measured from various single fiber characterization techniques, direct compression furnished data closer to that measured from composite compressive tests.

X-ray Diffraction Studies of the Axial Tensile Modulus of Rigid-Rod Polymer Fibers

ABSTRACTWe report the design and use of a device to measure the axial tensile modulus of high modulus fibers by following the change in the meridional X-ray spacings as a function of applied tension. The device, which mounts on a Picker 4-circle automated diffractometer, applies tension to the fiber sample by a cantilever arrangement. Tension is measured by a strain gauge bridge on the cantilever arm. The tension is adjusted and read by the control computer, a VAX 11/730. Measurements made on PBZT and PBO fibers before and after heat treatment are reported. For PBZT fibers (as spun, and heat treated at 525° C and 650° C) with tensile moduli of 186, 283 and 290 GPa, the X-ray determined moduli are 348, 385 and 395 GPa. For PBO fibers (as spun and heat treated at 600° C and 665° C) with tensile moduli of 166, 318 and 290 GPa, the X-ray determined moduli are 387, 477 and 433 GPa. These modulus values are to be compared with theoretical values presented by Wierschke in the previous paper and sonic modulus values discussed by Jiang et al in the following paper.

Microstructure of high modulus solid state extruded polyethylene: 1. Electron microscopy studies of 12, 24 and 36 × EDR

The microstructure of a series of solid state extruded polyethylenes for two molecular weights ( M w = 59 000 and 200 000) were examined by electron microscopy. The sample extrusion draw ratio varied from 12–24–36 ×. The axial tensile modulus increases almost linearly with draw ratio from 10 GPa (12 ×) to 40 GPa (36 ×). The extrudates consist of ribbon-like aggregates of 120–250Ådiameter microfibrils. Dark field electron microscopy indicates an increase of the average axial crystallite size with increasing extrusion draw ratio. The 12 and 24 × lower molecular weight samples have microstructures similar to conventionally drawn fibres, i.e. crystalline regions alternate with noncrystalline regions along the fibre axis. The low molecular weight 36 × sample and the high molecular weight 24 × sample contain broader crystalline size distributions and a small component of very long crystals (1000–8000Å). Moreover, individual fibrils of these highest modulus extrudates do not display fibre symmetry but consist rather of sequences of diffracting crystallites (crystallite colonies) indicating, by their coherence, the presence of thin intercrystalline bridges or needle crystals.