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This study aims to assess the morphology and properties of fibers extracted from a wild natural plant largely available in Algeria known as Juncus effusus L. (JE). The morphology and diameter of the fiber bundles extracted from the stem of the JE plant were characterized by optical and scanning electron microscopy. The functional groups of the extracted lignocellulosic JE fibers were studied by FTIR, their thermal degradation behavior was investigated by TGA and their crystallinity was determined using X-ray diffraction technique. In addition, mechanical characterization was carried out using tensile tests on the lignocellulosic fiber in order to evaluate their strength, strain at break and Young's modulus. In view of the dispersion in the obtained experimental results, the latter were analyzed using the Weibull statistical laws with two and three parameters. [ABSTRACT FROM AUTHOR]

The paper describes from a statistical perspective the diameter-dependence tensile strength and Young’s modulus in 40 sisal fibres samples. The fibres tensile properties depend significantly upon their diameter, which has been determined using optical and SEM microscope techniques. Further characterisation of the sisal fibres has been carried out using FT-IR and DSC techniques. The fibres’ ultimate tensile strength and Young’s modulus have been evaluated using four different estimation methods from two and three-parameter Weibull distribution statistics. We show the significant sensitivity of the Weibull predictions versus the number of fibres samples used in the distributions, with the Weibull modulus m σ obtained from our results being 10% smaller compared to what is reported in open literature. The scatter of the mechanical properties of the sisal fibres shown in this work is also compared to analogous distributions present in other works. [ABSTRACT FROM AUTHOR]

The work describes the manufacturing and tensile static behaviour of natural fibres produced with novel extraction techniques. The fibres are extracted using two new methods, one consisting of immersing the blades of the Agave leaves in water for 10-13 days in a container, and another sustainable extraction process during which the Agave leaves are buried in earth for 90 days. Single fibre tensile tests have been performed at four gauge lengths to assess the effect of the gauge length over the tensile strength and Young's modulus. The results have been analysed through a two-parameter Weibull distribution to quantify the degree of variability in fibre strength and Young's modulus at different gauge lengths for the two extraction methods. Strong sensitivity of the mechanical properties of the fibres has been observed based on the production methods used. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stiffness loss model for cyclic fatigue of sandwich panels in 3-point bending. [•] Model is identified through reduced number of measured parameters. [•] Model allows assessing the fatigue life of sandwich panels with limited number of available data. [•] Comprehensive experimental investigation with fracture modes of composite sandwich panels. [ABSTRACT FROM AUTHOR]

Abstract: The work describes the quasistatic tensile and fatigue behaviour of as-received sisal fibres. Natural-based reinforced composites are gaining significant interest within the structural community, due to their interesting mechanical properties, recyclability and environmentally-sustainable production and use. Natural fibres such as sisal constitute an excellent reinforcement material, due to the low extraction costs from plants, and high level of recycling involved in their manufacturing process. In this work the diameter, Young’s modulus, strength and strain to failure over 15 different samples are measured and compared against data from open literature. Tensile cyclic fatigue loading at eight loading levels (from 0.6 to 0.95) has been carried out. The maximum forces involved (between 9N and 22N) are considerably higher than the ones used previously in open literature, and lead to significant dependence of the hysteresis loops, energy dissipation and S–N behaviour of the sisal fibres versus the cycle and loading ratio levels. The results obtained from this work can be used to predict from a fatigue and structural integrity point of view the behaviour of sisal-based reinforced composites with high load bearing capability, and extend the design envelope of this class of natural-reinforced materials. [Copyright &y& Elsevier]

Abstract: The work describes the fibre extraction, manufacturing and testing of biocomposites made from cactus fibres and polyester matrix. A novel fibre extraction process has been developed, allowing the production of fibres from cactus cladodes with three distinct architectures in terms of microstructure morphology. Biocomposites with polyester matrix have been fabricated, and subjected to tensile and flexural loading. The flexural mechanical properties have been also identified through cyclic (1.5Hz) 3-point bending tests at different loading ratios (0.60–0.95) and up to 106 cycles following the ASTM D790 standard. The cactus/polyester composites show a flexural modulus significantly higher compared to their tensile analogous, and large energy dissipation per unit volume at low cycles and high loading levels. [Copyright &y& Elsevier]

Abstract: This work presents a novel formulation for a Voronoi-type cellular material with in-plane anisotropic behaviour, showing global positive and negative Poisson’s ratio effects under uniaxial tensile loading. The effects of the cell geometry and relative density over the global stiffness, equivalent in-plane Poisson’s ratios and shear modulus of the Voronoi-type structure are evaluated with a parametric analysis. Empirical formulas are identified to reproduce the mechanical trends of the equivalent homogeneous orthotropic material representing the Voronoi-type structure and its geometry parameters. [Copyright &y& Elsevier]

Abstract: This work presents the results related to the behaviour of cylindrical concrete specimens reinforced by external wrappings made of unidirectional carbon fibre/epoxy and bidirectional glass/polyester layers. The specimens have been subjected to a new uni-axial compression technique, consisting in sequential loading of the same sample, with the first loadstep terminated prior to failure of the column. Four types of jacketed specimens by glass fibre (GFRP), and one by a carbon fibre (CFRP) composites have been examined. The results obtained show that the CFRP-reinforced columns provide a significant increase in ultimate compression stress compared to the GFRP-reinforced ones reinforced. The damage mechanisms of the columns wrapped by the composite layers strongly depend on the reinforcement chosen. The hybrid composite jackets proposed in this work show also a remarkable increase in compressive strength and maximum radial strains, coupled with a significant low cost of the raw materials involved. [Copyright &y& Elsevier]

Abstract: We present the experimental results related to the mechanical behaviour under tensile static, fatigue and compressive relaxation loading of closed cell PVDF electret foams under different loading ratio conditions. The specimens are statically loaded until 60% of their ultimate displacement, and subsequently subjected to cyclic loading under displacement control. The static tests show a stress–strain behaviour and failure mode similar to the one of other polymeric closed cell materials, such as polymetacrylimide-based foams. The fatigue tests show an evolution of the stiffness degradation over the levels of cycles characterised by three distinct phases. The behaviour of the energy dissipated versus the loading ratios and numbers of cycles applied is discussed in this paper, as well as the comparison between the compressive fatigue behavior recorded on similar classes of foams. The compressive relaxation behaviour shows a two-phase dependence over the loading time, with increasing modulus for higher loading ratios, and absence of an asymptotic modulus for long time exposure. [Copyright &y& Elsevier]

Abstract: In this paper, we present a comparative analysis between the cyclic loading tensile behaviour of conventional and auxetic thermoplastic PU foams. While the two types of foam share the same base material (open cell PU–PE), one batch is transformed into an auxetic one (i.e., negative Poisson’s ratio) using a special manufacturing process involving moulding and exposure to particular temperature profiles to stabilise the transformation of the microstructure. The effect of the stiffness degradation and accumulation of energy dissipation versus the number of cycles are discussed for different loading levels r. The results show that the fatigue behaviour until failure, subjected to cyclic loading depends on the loading levels and occur in three stages. The results obtained shows also that the auxetic foam have enhanced characteristics under static loading and tensile fatigue compared to the conventional parent phase form. [Copyright &y& Elsevier]

Abstract: This work presents a comparative analysis between the cyclic loading compressive behaviour of conventional, iso-density non-auxetic and auxetic (negative Poisson’s ratio) thermoplastic polyurethane foams. While the three types of foam share the same base material (open cell rigid PU), one batch is transformed into auxetic (i.e., negative Poisson’s ratio) using a special manufacturing process involving moulding and exposure to particular temperature profiles to stabilize the microstructure transformation. The specimens have been loaded in cyclic compression with a sinusoidal waveform in displacement control. The static tests show the specific stress–strain compressive mechanical behaviour of these auxetic thermoplastic foams, opposite to conventional ones and other similar data on auxetics available in open literature. The effect of the load loss, stiffness degradation, the evolution of dynamic rigidity and accumulation of energy dissipation versus the number of cycles are discussed for different loading levels. The analysis of the results shows that the fatigue behaviour until failure occurs in two stages, subjected to cyclic loading, depends on the loading level. The hysteresis loop tends to close itself as function as the number of cycles N, while the slope of the dynamic stiffness decreases with increasing N, therefore with decrease of dissipated energy. The energy dissipated by the auxetic foams is significantly higher than the one from conventional parent phase and the iso-density foams at every number of cycles and loading level. [Copyright &y& Elsevier]

Abstract: The authors discuss the use of an artificial neural network (ANN) to estimate fatigue lifetime of a sandwich composite material structure subjected to cyclic three-point bending loads. A total of 27 samples (three different loading levels for nine samples each) were investigated to provide training, validation and testing data for a series of multi-layer perceptron ANNs. The networks were implemented using both conventional maximum likelihood and Bayesian evidence based training algorithms. It was found that the Bayesian evidence based approach provided a superior and smoother fit to the experimental data. Completely independent fatigue tests were conducted at intermediate levels of loading to evaluate the capacity of the fitted ANN model to interpolate to previously unseen regions of data. Excellent agreement was obtained between the model predicted outputs and the new experimental data. The capability and estimation of predication error when using the Bayesian technique is discussed along with the application of the model to generate classical S–N lifetime curves. [Copyright &y& Elsevier]

Abstract: In this paper analytical and finite element (FE) simulations are carried out to calculate the in-plane Poisson’s ratio and Young’s moduli of a new centresymmetric honeycomb configuration under uniaxial loading. Opposite to similar re-entrant honeycomb structures studied in the past, the new re-entrant unit cell topology takes into account possible manufacturing constraints typical of production routes like Resin Transfer Moulding (RTM) or Rapid Prototyping (RP). The results obtained through the analytical and FE analysis show a significant decrease of the Poisson’s ratio for the internal cell angle between −20° and +20° compared to the classical re-entrant configurations exhibited in literature. The results also show that the presence of edge corners in the unit cell honeycomb configuration gives rise to a cellular structure with enhanced flexibility compared to the classical centresymmetric one. The results obtained by the analytical model show good agreement with the Gibson and Ashby rib-bending model when the honeycomb configuration reduces to the theoretical layout without modifications due to manufacturing constraints. [Copyright &y& Elsevier]

• The date palm mesh fibers have been incorporated into mortar. • The mechanical behavior of the bio-fiber reinforced mortar has been analyzed using 3-point bending tests. • A surface response methodology (SRM) has been developed to optimize the experimental results. • The optimized reinforced mortar provides a 50% increase of the flexural stress compared to the reference configuration. As part of local agricultural date palm waste valorization, this work describes bio-composites made with a cement matrix reinforced with short Mesh date palm fibers for non-structural civil engineering applications. The study focuses in particular on investigating the influence of four parameters on the bending and compression properties of the bio-fiber reinforced mortar: the fiber content, length, NaOH concentration and immersion times of those fibers in the chemical solution. For this purpose, flexural and compression tests have been carried out. An experimental design representing 27 combinations of the above four parameters has been established to minimize the number of experimental trials and build a surface response methodology (SRM) using the design expert software 12 code. The results obtained show that the incorporation of mesh date palm fibers into the mortar improve the mechanical properties of the bio-fiber reinforced mortar. The bending stress of beams with the bio-based reinforcement increases 27.5% compared to the reference configuration; the bending modulus conversely improves by 18.9%. Compression stress and modulus showed increases around 46.6% and 36.3%, respectively. The objective function used to optimize the mechanical properties provides however an increase in bending stress and modulus around 50.0% and 20.0%, respectively, compared to the reference mortar case. The parametric design of the bio-composites that provided the best compression performance was very close to the one identified by the minimum of the objective function. Confirmatory experimental tests results compared to those from the objective function model developed show good agreement, with 3.3% and 3.8% differences for the bending stress and modulus, respectively. [ABSTRACT FROM AUTHOR]

• Quasi-static and cyclic fatigue traction of long fibers of date palm fruit branches. • Characterization by SEM of the fiber of date palm fruit branches. • Analysis of load-displacement hysteresis curves. • Interpretation and discussion of S-N curves. This work describes the quasi-static tensile behavior and cyclic fatigue of technical fibers from date palm tested for the first time according to the authors' knowledge, which can be used in the reinforcement of green composites.The values of the stress and strain at failure and Young's modulus for18 samples tested under quasi-static tensile loading are compared with results reported in the literature for other fibers. Cyclic fatigue tests were performed at a frequency of 2 Hz under sinusoidal solicitation for different loading levels ranging from 0.6 to 0.95 corresponding to maximum recorded forces of 15.36 and 39.82 N, respectively. The evolution of the force as a function of the number of cycles was recorded. This allows us to follow the stiffness degradation. The load-displacement hysteresis curves show the influence of the number of cycles and the loading level on the size and shape of the hysteresis loops, allowing the calculation of the dissipated energy per cycle for the technical fibers. [ABSTRACT FROM AUTHOR]

• Vascular bundles (VBs) and fiber strands (FSs) have been extracted from date palm rachis. • The morphology, surface roughness, physicochemical and thermal properties were analyzed. • The low density of VBs and FSs promotes lightweight applications. • FSs have tensile strength (530.5 ± 115.2 MPa) more than 4 times higher than VBs. • This research qualifies VBs and FSs for use as reinforcement in composite materials. Date palm rachis fibers are rich in cellulose, relatively inexpensive, and readily available in Algeria. The aim of this study is to investigate the morphology, structure, mechanical and physicochemical characteristics of both vascular bundles and fiber strands extracted from date palm rachis. The difficulties encountered are associated to the extraction of the fibers without damaging them. The study focuses on the morphological and surface roughness analysis using optical and scanning electron microscopies (SEM), and a non-contact 3D profiler. The chemical, physical and thermal properties have been studied using Fourier-transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The mechanical properties were accessed by tensile tests and they were analyzed using two-parameter Weibull distribution. [ABSTRACT FROM AUTHOR]

In rural, arid, and desert areas such as in southern Algeria, constructions are generally based on the use of raw earth due to its availability, abundance, and low price. In addition, raw earth-based constructions require continuous repairs and restorations. Therefore, this work aims to develop a new eco-friendly, low-cost, and sustainable composite, which is adapted to the local climate and meets the structural requirements of earthen constructions. The new composite blocks are made from compressed raw earth and reinforced with date palm stems (DPS), moistened, and then statically compacted. The use of DPS is part of the recovery process of date palm waste that can be used as reinforcement in blocks and can also lead to the improvement of the mechanical and thermal performance. The chemical and mineralogical composition of the raw earth is first determined by X-ray fluorescence and X-ray diffraction, while its physical, chemical and mechanical properties are also determined using different international standards. Two varieties of DPS, namely the Teggaza and Telemso ones are tested under tensile loading, where the latter shows better mechanical properties compared to classical reinforcements in compressed earth blocks (CEB). Thirty reinforced CEB formulations have been here developed, with different weight content of DPS fibres (0.5, 1, 1.5 and 2 wt%), length (1, 2 and 3 cm), morphology (smooth, rough, and mixed) and DPS with four types of treatments (immersion, boiling, autoclaving and hornification). This work also provides an analysis of the mechanical characteristics of the composite blocks by highlighting the influence of the different parameters (i.e., percentage, length, morphology, and treatment of the DPS) on the bending and compressive strengths after drying for 7 and 28 days. [ABSTRACT FROM AUTHOR]

The work describes the mechanics of novel woven jute fibers reinforced polyester (JFRP) laminates under uniaxial and multi-axial static and fatigue loading cases. JFRP laminates with 25% fiber volume fraction (FVF) have been manufactured using a hand-layup molding technique at a low pressure. Static uniaxial tests have shown that these novel bio-reinforced laminates have an ultimate tensile strength around 42 MPa under tensile loading and 7.5 N-m under torsional loading. The Multi-axial (tension/torsion) static tests yield an ultimate strength of 21.7 MPa and 5 N-m for tensile and torsion loading conditions, respectively. Fatigue tests have been carried out under displacement and angular control at three different loading levels with a frequency of 5 Hz. The fatigue tests results are extensively analyzed using stiffness degradation behavior, hysteresis loops, energy dissipation and strain versus number of cycles (ɛ-N) diagrams. The fatigue endurance limit (over one million cycles) for JFRP is achieved at a stress level of 65% of ultimate displacement. The implication of this work is the use of these materials in areas such as car and aircraft interiors promises to significantly reduce weight, cost and carbon footprints without sacrificing performance. [ABSTRACT FROM AUTHOR]

Steel pipelines are increasingly essential for many applications, including the transport of oil, natural gas, and soon hydrogen gas. Steel pipelines are subject to harsh operating conditions. Corrosion is considered to be the most common type of failure in steel pipelines. This report focuses on corrosion and assessment in gas and oil pipelines. The most common method of repairing corroded pipelines by composite repair is included in the review. Based on conservative codes and deterministic and reliable FEM approaches, different tool designs and models of corroded pipelines without and with repair are summarized and compared. The evaluation of defects in determining the failure pressure of pipelines and the study of the contribution of composite wrap repair to corroded pipelines are discussed. • Review paper. • Failure pressure prediction of corroded pipelines. • Repairing corroded pipelines. • Composite wrap contribution based on synthetic and natural fibers. • Conservative codes, deterministic and reliability FEM design of corroded pipelines approaches. [ABSTRACT FROM AUTHOR]

The work describes the out-of-plane properties of a curved wall honeycomb structure evaluated using analytical models and finite elements techniques. Out-of-plane properties are calculated using a theoretical approach based on energy theorems and validated using a full-scale finite element technique to simulate transverse shear tests. The effects of the curvature of the walls and the depth of the honeycomb cells on the out-of-plane elastic constants are evaluated and excellent agreement is observed between theoretical and numerical models. These curved cell wall honeycombs feature specific (i.e., relative density weighted) highly tailorable upper shear bounds that shift their maximum values with the radiuses of the curved cell walls at different internal cell angles. Finally, it is also shown that these honeycombs exhibit a particular topology with a specific upper boundary independent of the non-zero curvature cell wall adopted and only dependent upon the internal cell angle. [ABSTRACT FROM AUTHOR]

In this paper, analytical and 3D numerical models are developed to investigate the mechanical behavior of sandwich pipe under internal pressure loading. The suggested models provide an exact solution for stresses, strains and displacement on the sandwich pipe, which is made of epoxy material for the core layer and reinforced materials with an alternate-ply for the skin layers. The aim of this analysis is to evaluate the potential applications of jute and pineapple leaf fiber (PALF) bio-fibers in order to replace glass synthetic fibers generally employed in sandwich pipes. In this subject, a failure analytical analysis was developed using TSAI-WU criterion. The results of stress, strain and displacement distribution through the thickness are presented for the analytical and numerical models. The comparison between the both models results show a very good agreement. In order to increase the rigidity of a biocomposite sandwich and reduce the gap compared with a synthetic sandwich, a gradual reinforcing of layer numbers was chosen, which permitted the best behavior. The ultimate pressure and safety factors obtained by increasing biocomposite layers are significant for composite transportation pressure pipelines, especially for sandwich pipe based on PALF/epoxy. • We aim at modeling a sandwich pipe under internal pressure loading using analytical and 3D numerical models for failure analysis. • The structure is a made of epoxy material for the core layer and reinforced materials with an alternate-ply for the skin layers. • Evaluate the potential applications of bio-fibers in order to replace synthetic fibers generally employed in sandwich pipes using TSAI-WU criterion. • Substituting synthetic fibers by bio-fibers yields a satisfactory result by increasing the number of layers. [ABSTRACT FROM AUTHOR]

Abstract: This study focuses on the mechanical response of a hybrid solution dedicated to gaseous hydrogen storage. This solution is made of a carbon/epoxy composite overwrapped on a metal liner first coated with intermetallic material. The composite helps to reinforce the structure, while the liner prevents it from any leakage. In case of deficiency, the intermetallic material behaves as a sponge and interrupts the leakage by absorption and micro-cracks reduction. This hybrid solution or this specific use of intermetallic material has never been presented before. The laminate composite is anisotropic, whereas the liner is an elastic–plastic material. The intermetallic is purely thermo elastic and its study is limited to its mechanical contribution. Using these hypotheses, the suggested analytical model provides an exact solution for stresses and strains on the cylindrical section of the hybrid solution submitted to thermomechanical static loading and hydrogen leakage. The swelling effect of the intermetallic on the behavior of the structure is then investigated. [Copyright &y& Elsevier]

Due to the viscoelastic properties of cork and polymeric matrices, stress relaxation and creep behaviour of multiphase composites incorporating cork are important properties that should be considered at the design stage. For this purpose, composites with the same lay-up but with different fibres were manufactured with neat epoxy resin and epoxy resin filled with cork powder. It was concluded that higher values of relaxation and creep displacement occur when Kevlar fibres are used in place of carbon fibres and, for both, when cork powder was introduced into the resin. Considering the strain correspondent to 150 MPa for Kevlar composites, the difference observed between the initial and final bending stress is around 19.1 MPa for laminates with neat resin and 13.5% higher for laminates with matrix filled by cork powder. In terms of creep and comparatively to the neat resin, the displacement increases 24.6% when the resin incorporates cork powder. Regardless of whether the resin was pure or filled with cork powder, the same trend was observed for carbon composites, but with less expressive values for the same comparisons previously established. Finally, the maximum error obtained between the theoretical and experimental results of 0.6% for all conditions tested shows that the Kohlrausch-Williams-Watts (KWW) function can be used to accurately predict the relaxation stress response. In terms of creep response, this function was compared with the Findley model and, regardless of the success obtained with both, the best predictions are reached with the KWW model. [ABSTRACT FROM AUTHOR]