Natural fibre composites have been trending in the industries recently due to their better recyclability, renewability, biodegradability. Fused Deposition Modelling (FDM) is one of the widely used ...additive manufacturing process for the fabrication of simple and complex structures. In this study, hemp/PLA 3D printed honeycomb sandwich structures were fabricated by FDM process and mechanical behaviour was characterized. Initially, the tensile behaviour of hemp fibre/PLA filaments and the 3D printed composite specimens with an infill angle of 0°/90°, -45°/ + 45° were investigated. Honeycomb cores were fabricated and their mechanical behaviour in flatwise, edgewise directions were analysed. Later, honeycomb sandwich structures were fabricated using core and skin parts. Compression and 4-Point bending tests were performed to characterize the mechanical behaviour. Analytical analysis was also performed to predict the mechanical properties of the honeycomb sandwich structure knowing the properties of the cell wall material. Some small-scaled automotive and aerospace prototypes were fabricated to assure the application of this methodology.
Natural fiber composites are widely used in a several industrial applications due to their outstanding biodegradability and recyclability. Thermal compression molding is a rapid and easy method to ...fabricate composite sheets. To better understand the manufacturing process and evaluate the mechanical properties of hemp woven fabrics reinforced thermoplastic composite at elevated temperatures, a detailed investigation is required. In this study, composite sheets were initially fabricated using hemp fiber fabrics (taffeta and serge 2×1) and polypropylene sheets by the thermal compression molding process. Mechanical tests (uniaxial, shear, and biaxial) were carried out at temperatures ranging from 20 to 160 ∘C in order to estimate the mechanical properties of composite sheets. Non-linear behavior was observed during the loading due to the unbalanced weaving pattern of hemp fabric. The biaxial behavior of the composite was estimated using a theoretical method for fabric strength prediction taking into account the interaction effect between the yarns. The experimental results demonstrate that, at high temperature, the polymer softens and the fiber reinforcements dismantle which resulting in a decrease in the mechanical properties of the composite. Two analytical models (Ha & Springer and thermal expansion coefficient) were also proposed to estimate the thermo-mechanical properties of natural fiber composites subjected to various temperatures.
This article exposes the beginnings of a new field which could be named as “plasmomechanics”. Plasmomechanics comes from the convergence between mechanics and plasmonics. Here we discuss a relatively ...recent topic whose technological aim is the development of plasmonic strain sensors. The idea is based on the ability to deduce Au nanoparticles (NPs) distance distributions from polarized optical extinction spectroscopy which could thus give access to material strains. Variations of interparticle distances distributions can indeed lead to variations of plasmonic coupling and thus to material color change as shown here experimentally and numerically for random Au NP assemblies deposited onto elastomer films.
A methodology for radiation lot acceptance at the board level is proposed. A worst case analysis of a dc/dc converter board has been performed per two analytical methods and per a Monte Carlo ...simulation. Six samples of the board have been tested to confront the analysis results with temperature effects (<inline-formula> <tex-math notation="LaTeX">- 55~^{\circ } </tex-math></inline-formula>C, <inline-formula> <tex-math notation="LaTeX">+ 25~^{\circ } </tex-math></inline-formula>C, and <inline-formula> <tex-math notation="LaTeX">+ 125~^{\circ } </tex-math></inline-formula>C), aging effects (1300 h at <inline-formula> <tex-math notation="LaTeX">120~^{\circ } </tex-math></inline-formula>C), and ionizing dose effects 20, 50, and 105 krad(Si). The tested board functions are found to be almost only dependent on the temperature, whereas significant degradation by aging and dose could be expected from the analysis.
Natural fibre reinforced composites are emerging as the alternative of synthetic composite materials in several applications due to their limited recyclability and biodegradability. In this study, ...the tensile behaviour of hemp yarns detached from taffeta and serge fabrics were investigated. Experimental analysis was performed to characterize the crimped yarn properties. Analytical analysis was carried out in order to model and predict the mechanical behaviour of hemp fibre yarns under tensile loading. An inverse optimization approach was also adapted to optimize the mechanical properties of the yarns numerically.
Nowadays natural fibre composites have gained great significance as reinforcements in polymer matrix composites. Composite material based on a polymer matrix reinforced with natural fibres is ...extensively used in industry due to their biodegradability, recyclability, low density and high specific properties. A study has been carried out here to investigate the fibre volume fraction effect of hemp fibre woven fabrics/PolyPropylene (PP) composite laminates on the tensile properties and impact hammer impact test. Initially, composite sheets were fabricated by the thermal-compression process with desired number of fabric layers to obtain composite laminates with different fibre volume fraction. Uniaxial, shear and biaxial tensile tests were performed and mechanical properties were calculated. Impact hammer test was also carried out to estimate the frequency and damping parameters of stratified composite plates. Scanning Electron Microscope (SEM) analysis was performed to observe the matrix and fibre constituent defects. Hemp fabrics/PP composite laminates exhibits viscoelastic behaviour and as the fibre volume fraction increases, the viscoelastic behaviour decreases to elastic behaviour. Due to this, the tensile strength increases as the fibre content increases. On the other hand, the natural frequency increases and damping ratio decrease as the fibre volume fraction increases.
Two strain localization modes: the Piobert-Lüders band propagation and the development of necking, were investigated in uniaxial tensile tests for a low alloyed and low carbon steel. These two ...macroscopic localization phenomena were simultaneously monitored by speckle interferometry (ESPI) and acoustic emission (AE). The coupling of these two experimental techniques gives complementary information about strain localization features and mechanisms. For Lüders bands, it was found that the acoustic activity heard during the travel of the Piobert-Lüders band varies in closely correlated to the tensile force fluctuations, the relations between strain rate, band velocity, band width and plastic strain were investigated. Although the strain rate in the wake of the wave front is not always zero, the acoustic activity remains concentrated in the wave front itself. For necking, the acoustic activity is found to decrease regularly through the homogeneous plasticity stage and the diffuse necking stage and then increases when the localized necking starts, while ESPI patterns show a gradual strain concentration.
Localization that occurs at the end of the tensile test of a ductile 316L stainless steel has been followed in detail by in-plane Electronic Speckle Pattern Interferometry (ESPI). A global ...description of the whole strain-rate field with an analytical function and physical descriptors such as band width, band inclination and maximum strain rate is proposed. The description with two straight bands of constant amplitude along the width of the specimens is valid from the beginning of the diffuse necking to the fracture of the specimens. It allows distinguishing between two localization scenarii which occur for specimens with a different width to thickness ratio, one with a fracture inclined along the width and the other with a fracture inclined in the thickness. For the former, the two bands keep a constant angle while for the latter, the two bands rotate progressively until they become perpendicular to the tensile direction. The bandwidth can be defined and monitored during the whole necking evolution.
Advances in technology have provided fresh generations of stiff polypropylene block copolymers for gravity sewerage applications. The aim of this study is to further enhance the stiffness of these ...materials through the incorporation of inorganic fillers. In this study, three talc filled PP and one glass fiber filled PP composites were characterized in order to be used as a middle layer in a three‐layer sewage pipe. The obtained results showed an increase of approximately more than 100% and 250% in tensile and flexural moduli by the use of 30%–50 wt% talc‐filled PP and 30 wt.% glass fiber‐filled PP, respectively. This high increase in the rigidity of the material would allow manufacturing pipes with improving ring stiffness. Composites filled with 30 wt% talc or glass fiber showed good filler‐matrix interaction and good filler distribution and dispersion. However, reduced filler‐matrix interaction was observed in the case of the composite filled with 50 wt% talc. In addition, the use of Differential Scanning Calorimetry analysis revealed that the addition of fillers enhanced the crystallization temperature of the polypropylene matrix. Furthermore, Thermogravimetric Analysis showed that the high modulus PP grade retained its thermal stability in the various composites.
Improvement of the ring stiffness of a plain pipe by the development of a multilayer composite pipe.
This paper investigates the characterization of the microstructure, hardness, and residual stress distributions of MIG-welded high-strength low-alloy S500MC steel. The T-joint weld for 10-mm-thick ...plates was joined using a two passes MIG welding technology. The contour method was performed to measure longitudinal welding residual stress. The obtained results highlighted a good correlation between the metallurgical phase constituents and hardness distribution within the weld zones. In fact, the presence of bainite and smaller ferrite grain size in the weld-fusion zone might be the reason for the highest hardness measured in this region. A similar trend of the residual stress and hardness distributions was also obtained.
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