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In this study, the morphological, physical, and tensile properties of flax were experimentally investigated at three different scales (single fiber, yarn and unidirectional fabric). The cross-sectional area was determined directly using microscopic image and indirectly via linear density with gravimetric and vibroscopic methods. All specimens were tested in tension until failure. The results showed that measured properties and their variability were scale-dependent. The tensile strength and modulus of elasticity were gradually decreasing with the scale and the variabilities were decreasing when going from fibers to yarns and fabric. This difference in the properties should be considered for any multi-scale analysis of the flax reinforcement. The average failure strains of single fiber, yarn and fabric were 2% (±30%), 1.7% (±12%) and 1.7% (±2.8%), respectively. Due to the consistency of failure strain at different material scales, it can be recommended as design criterion. The results of this study can be used for better design and preparation of plant-based natural fiber reinforced polymer composites.

WOS: 000428487200012 Several formulations of wood-plastic composites and a particleboard were fabricated with combining zinc borate biocide at different retention levels during the manufacturing process. The treated specimens were exposed to a field test under protected above ground conditions for 7 years in southern Japan. During biannual inspections, the specimens were visually inspected and graded for decay and Formosan subterranean termite damage. While zinc borate retention levels tested were able to protect the particleboards from decay activity for 7 years, their efficacy was lower against termite attack. The retention levels tested up to 2% (w/w) helped to reduce termite damage noticeably but failed from full protection (e.g. rating 10) indicating higher zinc borate loadings are required in particleboards if they will be utilized in southern Japan climatic conditions. Wood-plastic composites were also more durable against fungal damage during the 7 years exposure period but this condition seems changed last 18 months since some lower decay ratings were recorded even for zinc borate embedded formulations. While termite destruction diminished significantly with zinc borate integrated formulations, higher retentions might be recommended as threshold for full protection in wood-polypropylene composites.

International audience; Composite processing strongly affects the size of lignocellulosic fibers, and consequently the mechanical properties of the final product. Using a reliable method for the analysis of fiber length and diameter distributions is thus crucial for the understanding of fiber behavior during processing. In this study, three different techniques, X-ray microtomography, 2D scanning and automated fiber analyzer, were compared in terms of their reliability for the characterization of dimensions of two kinds of lignocellulosic fibers, hemp and miscanthus, in polymer-natural fiber composites. Statistical analysis was employed to interpret fiber size distributions. The study confirmed that interpreting the dimensions of natural fiber is still a difficult task. The inherent limitations of the measuring methods make each technique complementary to the others in terms of length scale. The choice of the technique is, therefore, strictly dependent on fiber dimensions and the aim of the work.

Injection molded short fiber reinforced composites (SFRC) have different local fiber orientation distribution (FOD) at every point. SN curves of short fiber reinforced composites are known to depend on the fiber orientation distribution. Such materials also suffer from continuous loss of stiffness during cyclic loading. It is not known whether the loss of stiffness is different for SFRC with different FOD. A statistical analysis of the loss of stiffness curves is presented in this paper. Tension-tension fatigue experiments are performed and loss of stiffness is collected for every data point in the SN curve. A systematic method for comparing the loss of stiffness is developed. It is concluded that the difference in loss of stiffness curves for coupons of SFRC with different FOD is not statistically significant. (C) 2016 Elsevier Ltd. All rights reserved.

Talc is broadly used in the ceramic materials industry, either as a basic raw material, or as filler, due to its chemical inertia, fragmentation proneness, thermal stability, and refractoriness. The mechanical activation is frequently employed in the direct enhancement of talc properties, and thereby in the design of talc based composites with advanced performances. The differences in the set of the process parameters measured before and after talc activation via ultra-centrifugal mill Retsch ZM-1, and their influence on the grain-size distribution related characteristics have been investigated. The mechanical treatments are energetically unsustainable procedures, therefore the talc activation was optimized on basis of assessment of the process variables (number of rotor revolutions, current intensity, activation period, circumferential rotor speed and mill capacity) effect on the final quality of product parameters (mesh sizes, cumulative oversizes, average grain size, level of micronization kinetics, mesh size appropriate to 95% micronized product cumulative undersize and specific surface area). The activated product parameters in all experimental sequences were obtained by the analytical procedure based on Rosin-Rammler-Sperling equation. Response surface method, standard score analysis and principal component analysis were used as a means of the optimization. Developed models showed r2 values in the range of 0.714–0.908 and they were able to accurately predict quality parameters in a wide range of process parameters. Standard score analysis highlighted that the optimal sample was obtained using sieve mesh of 120 μm set of processing parameters (SS = 1.0). Multiple comparison tests revealed that the optimal variation in the processing parameters could reduce the negative effect of talc samples inherent properties on the final score and improve the activation procedure energetic and economic sustainability.

WOS: 000333506500068, This paper presents test results of six concrete beams reinforced with longitudinal carbon fiber reinforced polymer (CFRP) bars and without vertical shear reinforcement. All beams were tested under a two-point loading system to investigate shear behavior of CFRP reinforced concrete beams. Beam depth and amount of CFRP reinforcement were the main parameters investigated. All beams failed due to a sudden diagonal shear crack at almost 45 degrees. A simplified, empirical expression for the shear capacity of FRP reinforced concrete members accounting for most influential parameters is developed based on the design-by-testing approach using a large database of 134 specimens collected from the literature including the beams tested in this study. The equations of six existing design standards for shear capacity of FRP reinforced concrete beams have also been evaluated using the large database collected. The existing shear design methods for FRP reinforced concrete beams give either conservative or unsafe predictions for many specimens in the database and their accuracy are mostly dependent on the effective depth and type of FRP reinforcement. On the other hand, the proposed equation provides reasonably accurate shear capacity predictions for a wide range of FRP reinforced concrete beams. (C) 2013 Elsevier Ltd. All rights reserved.

WOS: 000328801200006 The decay and termite resistance and effects of a robust leaching process on the efficacy of zinc borate-incorporated particleboard were examined. Particleboards (300 x 300 x 15 mm) prepared from particles of mixed wood species generated from demolished construction materials were incorporated with zinc borate at target retentions of 0%, 1%, 1.5% and 2% of the particle weight. An in-line treatment method was utilized to introduce the powdered chemical during the blending stage. ICP analysis indicated that the amount of zinc borate was not lost during manufacturing. Standard static bending tests demonstrated that there was no significant loss in mechanical properties. The decay and termite tests indicated that the efficacy of zinc borate at a higher retention was enough to suppress the biological activity, even after application of a robust leaching process. (C) 2013 Elsevier Ltd. All rights reserved. Japan Society for the Promotion of Science (JSPS)Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [P07171]; RISH, Kyoto University The first author extends his appreciation to Japan Society for the Promotion of Science (JSPS) for supporting this study through a post-doctoral fellowship grant (P07171), to RISH, Kyoto University, for support under the Visiting Professor program between April 1 and June 30, 2012, and to the late Dr. Kunio Tsunoda (who passed away on October 5th, 2011) for moral support at the initiation of the project and Ms. Nuriye Peachy for English proof readings of the manuscript.

Composites manufacturing involves many sources of uncertainty associated with material properties variation and boundary conditions variability. In this study, experimental and numerical results concerning the statistical characterisation and the influence of inputs variability on the main steps of composites manufacturing including process-induced defects are presented and analysed. Each of the steps of composite manufacturing introduces variability to the subsequent processes, creating strong interdependencies between the process parameters and properties of the final part. The development and implementation of stochastic simulation tools is imperative to quantify process output variabilities and develop optimal process designs in composites manufacturing.

In the recent past, experimental results of bond tests performed by several researchers on the performances of Fiber Reinforced Polymer (FRP) applied according to Near Surface Mounted (NSM) strengthening technique showed that mechanical properties of materials and surface properties of FRP reinforcement as well as the grooves geometry and the test set up can affect the bond of this strengthening system. An experimental program aimed to compare the bond behavior of different types of FRP materials applied on concrete blocks according to Externally Bonded Reinforcement (EBR) and NSM strengthening techniques has been presented and discussed in a previous paper, showing that the NSM technique could represent a sound alternative to EBR systems since it allows the FRP tensile strength to be better exploited. Herein the results of bond tests on different types of NSM reinforcement are analyzed in terms of bond-slip relationships in order to show the appropriateness of using simplified bilinear relationships. Moreover, further experimental results of bond tests available in literature and characterized by different types of bond failures have been selected and joined to those widely analyzed in this paper in order to provide an experimentally calibrated relationship predicting the maximum debonding strain in the FRP NSM reinforcement. (C) 2011 Elsevier Ltd. All rights reserved.

Natural fibres are studied as alternatives for man-made fibres to reinforce composites while keeping the weight lower. The assessment of the value of some commonly available tropical fibres for the composite industry starts with the determination of the strength, E-modulus and strain to failure through single fibre tensile tests. The mean strength and standard deviation is calculated following the normal and Weibull distribution resulting in the questionable benefit of applying the Weibull distribution. Furthermore, a correction method assesses the real fibre elongation from the measured clamp displacement. This procedure seems to be useful for strong, brittle fibres to produce more reliable results for the E-modulus and strain to failure.