This paper presents the design, development and testing of a low-cost Structural Health Monitoring (SHM) system based on MEMS (Micro Electro-Mechanical Systems) triaxial accelerometers. A new control system composed by a myRIO platform, managed by specific LabVIEW software, has been developed. The LabVIEW software also computes the frequency response functions for the subsequent modal analysis. The proposed SHM system was validated by comparing the data measured by this set-up with a conventional SHM system based on piezoelectric accelerometers. After carrying out some validation tests, a high correlation can be appreciated in the behavior of both systems, being possible to conclude that the proposed system is sufficiently accurate and sensitive for operative purposes, apart from being significantly more affordable than the traditional one.

This paper presented an experimental structural-scale test campaign used to analyze the flexural behavior of low-grade maritime pine (Pinus pinaster Ait.) duo timber beams reinforced with an internal glass fiber-reinforced polymer (GFRP) sheet. For this purpose, thirty (30) unreinforced duo beams and thirty (30) duo beams internally reinforced with a unidirectional GFRP sheet with an areal mass of 1200 g/m² were produced and tested. The addition of a low GFRP reinforcement ratio (1.07%) in the tension zone of the duo beams provided an average improvement of 8.37% in bending stiffness (EI) and an increase of up to 18.45% in ultimate moment capacity. In addition to this improved bending behavior, the internal GFRP reinforcements seemed to decrease the influence of wood singularities and wood heterogeneity on mechanical properties, which allowed for better characteristic values to be reached and for the achievement of results with less variability.

Research Highlights: The novelty of this study is the development of an accurate wood density estimation method based on a relatively brand new semi-destructive testing technique (drilling chips extraction). This method is especially crucial in the assessment of existing timber structures. Background and Objectives: Probing, drilling, and coring are non-destructive and semi-destructive techniques commonly used for timber density estimation in existing timber structures. Most of these techniques show poor or medium accuracy or are so expensive or destructive. This paper aims to obtain accurate estimation models for wood density in existing structures using the easy to use drilling chips extraction technique. Materials and Methods: 300 specimens (95 × 65 × 200 mm³) from ten softwood and hardwood species covering a wide range of density (from 350 to 980 kg·m⁻³) were tested after conditioning. The Wood Extractor device based on the drilling chips extraction technique was used in the radial and the tangential direction. Mass of the chips collected (drilling residue) from each drill was recorded. Results: Density obtained from drilling residue was not statistically significantly different between radial and tangential directions avoiding take into account direction when measuring. The density obtained in the whole specimens is slightly higher than the density obtained by drilling residue being this difference uniformly through the range of densities studied. Two different estimation models were presented with high determination coefficients (96% and 97%) and low standard errors. These results were similar to those obtained by other authors using core drilling but causing less damage. Conclusions: Drilling chips extractor is a simple, reliable and inexpensive method to estimate density in existing structures with accuracy.

Research Highlights: The novelty of this study is the deep analysis of the morphologic, geometric and mechanical performance of longhorn beetle larvae mouthparts. Furthermore, a metal nano identification of jaw reinforced parts was made. Background and Objectives: Analysis of insect mechanical properties has shown an important application in the develop of bionic technologies such as new materials, industrial machines and structural concepts. This study aims to determine the mechanical and geometric properties of longhorn beetle (Stromatium unicolor Olivier 1795) larvae mouthparts to improve the development of innovative cutting tools. In addition, this study obtains a nano identification of metals in the cuticle of the mouthparts, which will enable the development of new nontoxic and sustainable preservation agents against xylophagous insects based on nanoparticles. Materials and Methods: five third-larval-stage samples of Stromatium unicolor were used to study its mandible morphologic, geometric and mechanical properties. To this end, mouthparts were analyzed by several microscopic techniques using a scanning electron microscope, a stereomicroscope and an optical microscope. Composition analysis was performed using with two Analytical-Inca X-ray detectors, dispersive energy spectroscopy and dispersive wavelength spectroscopy. Results: The main geometric parameters of the insect jaw are the edge angle (β = 77.3°), maximum path depth of the insect (120 μm), length (800 µm) and mouthpart movement, which were identified and measured. The chemical analysis results of the jaw tissues shows the presence of zinc and manganese. Conclusions: The geometry and angles of the mouthparts can be applied in the fabrication of bionic self-sharpening cutting tools. Molecular compounds that form the reinforcing elements in the jaws can be used to develop wood preservatives based on nanometals and metal absorption and metabolism inhibitors.

In this study, dynamic hardness tests on solid and engineered wood flooring specimens of Eucalyptus globulus Labill. and Eucalyptus grandis W. Hill ex Maiden hardwoods were performed because nowadays, these fast-growing hardwoods are still scarcely employed for this use. Furthermore, another two examples of hardwood commonly applied on wood flooring, Quercus robur L. and Hymenaea courbaril L., were also tested. To compare their properties, a dynamic impact hardness test based on the impact of steel balls, with several diameters, and drop heights was developed. Accordingly, 120 solid wood flooring specimens and 120 engineering wood flooring specimens were producing with these four hardwood species. Dynamic impact tests were made with three steel balls of different diameters (30–40–50 mm), and they were carried out from five different drop heights (0.60–0.75–0.90–1.05–1.20 m). The impact of the steel ball drew the size of the footprint on the surface and this mark was measured with a digital caliper for both dimensions, diameter and depth, as footprint diameter (FD) and indentation depth (ID). Data from 3000 samples, corresponding to 120 different individual groups (4 species × 3 ball diameters × 5 drop height × 2 floor type) were analyzed. Results indicated that the variability of ID (CV between 19.25–25.61%) is much greater than the values achieved for FD (CV between 6.72–7.91%). Regarding the fast-growing hardwood species tested, E. globulus showed a similar behavior to traditional hardwood applied on wood flooring in Europe, Q. robur, and it could be a promising growth in the flooring industry. However, E. grandis showed the worst values compared to traditional hardwood in all test configurations.