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Abstract Dry carbon and glass fibre bundles were inserted into a ROHACELL® 71HERO Polymethacrylimide (PMI) foam core under a specific inclination angle and pin pattern in order to improve the impact damage tolerance and the fracture toughness of foam core sandwich. Impact tests were performed on pin-reinforced foam core sandwich panels with different pin-configurations at impact energies between 35 J and 70 J. X-ray computed tomography and ultrasonic C-scan were used to determine the damages in the foam core. At room temperature no cracks were observed in the foam core. Using carbon fibre pins led to the creation of thermally induced cracks in the foam core after impacts at −55 °C, which is critical for the integrity of the structure. The modification of the manufacturing process parameters and the use of glass fibre pins are two solutions to improve the impact behaviour at −55 °C by delaying the thermal cracks to higher impact energies. [ABSTRACT FROM AUTHOR]

Energetically weak points in thermally insulated building envelopes are formed by thermal breaks that are implemented to structurally connect external balconies to internal slabs. Current thermal breaks comprise stainless steel bars that penetrate the insulation layer and thus cause significant thermal losses. A new thermal break composed of highly insulating aramid and glass fiber-reinforced polymer (AFRP and GFRP) components and aerogel granulate insulation materials was developed and the first prototypes of the load-bearing components were experimentally investigated. The use of AFRP leads to an excellent thermal performance with linear thermal transmittance values of below 0.15 W/m K. The experimental prototype investigations confirmed the targeted ductile failure mode through concrete crushing in the component–concrete interfaces. The serviceability limit state conditions are met for a targeted balcony cantilever span of 4.0 m. The material-tailored components can be manufactured by fully automated processes such as filament and tape winding and pultrusion to economically produce large quantities within a short time. [ABSTRACT FROM AUTHOR]

The objective of this article was to experimentally evaluate timber–concrete composite beams in two different situations – with and without glass fiber reinforced polymer (GFRP). Four full-scale composite beams (5.4 m in length) were produced, two of which had reinforcement (nominal thickness of 10 mm) and two with no reinforcement. The fiberglass reinforcement was formed from the impregnation of unidirectional fiberglass cloth – effective thickness of 0.5 mm – with epoxy resin. The connection system consisted of steel hooks inclined at 45 degrees, bonded with epoxy adhesive to the holes previously drilled on the wood, whose apparent density at 12% moisture content was 0.79 g/cm 3 . The reinforced timber–concrete composite beams tested had performance efficiency of 79% and average rupture strength of 142.5 kN. Finally, the reinforced timber–concrete composite beams were analytically evaluated using the proposed method in Eurocode5, showing reasonable agreement with the experimental results. [ABSTRACT FROM AUTHOR]

The objective of this work is to enhance the mechanical properties of unidirectional [0] 8 and quasi-isotropic [0/±45/90] s glass-fiber-reinforced composites by ultrasonically dispersing alumina-nanoparticles in epoxy matrix. The well dispersed alumina-nanoparticles in epoxy resin significantly improved the mechanical properties of alumina-nanocomposites. Results from fracture characterizations of the nano-hybridized unidirectional laminates with different off-axis angles showed high improvements in the interfacial bond strength between nanophased epoxy and glass fiber. Therefore, the flexural strength, modulus, and fracture toughness of quasi-isotropic laminate are significantly improved. Results from free vibration tests showed that the beam free length has high effects on the natural frequencies and the both have insignificant effect on the storage moduli of the composite laminates. For the investigated materials, the storage moduli correlated well ( R 2 = 0.99962) with the flexural moduli. The damping ratios of the nano-hybridized quasi-isotropic and unidirectional laminates are improved by 62% and 60%, respectively. These improvements, which were achieved through conventional processing, are essentially for developing the structural components of automotive and aerospace industry. [ABSTRACT FROM AUTHOR]

Abstract: In the last decades, FRP composites have been widely used for constructing entire civil structures. One of the challenging issues for building with pultruded FRP composites is understanding the behaviour of bolted joints. In this paper, the results of a numerical analysis performed on different types of bolted composite joints with different geometry and subjected to tensile loads are reported. The aim of this study is to examine the distribution of shear stresses among the different bolts by varying the number of rows of bolts as well as the number of bolts per row. The study also considers the presence of variable diameter washers and their influence on the bearing stresses of composites with different fibre orientations. For verification of the validity of the analytical models, numerical results are compared to experimental results reported elsewhere. The results of this study showed that in multi-bolt joints, the load is not distributed equally due to varying bolt position, bolt-hole clearance, bolt-torque or tightening of the bolt, friction between member plates and at washer-plate interface. The results also indicated that in the presence of washers, the stress distributions in the fibre direction, varying fibre inclinations, are decreasing for each value of washer pressure. [Copyright &y& Elsevier]

Abstract: In this study, nano glass fibre-reinforced polymer (nano-GFRP) composite reinforcing bars (rebar) for concrete structures were fabricated, and their performance during prolonged exposure to water and alkaline solutions was evaluated. Nano-GFRP rebar was prepared using the pultrusion method by adding nanomaterials to vinyl ester resin. The nanomaterials, including silica (SiO2), alumina (Al2O3), and silicon nitride (Si3N4), were added to vinyl ester resin at 1, 3, and 5wt.%. After exposure to water and alkaline solutions for 50 and 115days, tensile strength tests were carried out, and the moisture diffusion coefficient was determined and compared with that of general GFRP rebar. The results indicated that the tensile residual strengths of nano-GFRP rebar and general GFRP rebar were almost the same after exposure to water, whereas the tensile residual strength of nano-GFRP rebar was higher than that of general GFRP rebar after exposure to alkaline solution. The moisture diffusion coefficient of the alumina and silicon nitride samples increased slightly after exposure to alkaline solution, but the silica sample had a higher moisture diffusion coefficient; however, the moisture diffusion coefficients of all nano-GFRP rebar samples were comparable to that of general GFRP rebar. [Copyright &y& Elsevier]

Abstract: The design of concrete structures reinforced with glass fibre reinforced polymer (GFRP) bars is influenced by their reduced stiffness and brittleness. In hyperstatic structures, the methodology used in force analysis depends on the ductility of the structural systems, which in this case, being essentially provided by the concrete, can be potentially increased by confining concrete in critical zones. This paper presents experimental and numerical investigations about the flexural behaviour of continuous beams reinforced with GFRP bars, namely of their service and failure responses, and the effect of increasing concrete confinement in critical cross-sections. A calculation procedure to quantify the confinement effect in beams due to the reduction of the spacing between shear stirrups is first presented. The experimental investigations comprised a comparative study in which two-span concrete beams reinforced with either GFRP or steel bars were tested in bending. In the former, the effect of reducing the shear stirrups spacing was analyzed together with the under- and over-reinforcement at the central support and midspan cross-sections, respectively. The development of a crack hinge in the continuity support zone highlighted the better performance of beams under-reinforced on the top layer with GFRP bars compared to “equivalent” beams reinforced with steel, namely at the resistance level. In addition, the confinement at critical zones increased significantly the strength and ductility. The numerical investigations included the development of non-linear finite element models for all beams tested – numerical results are in good agreement with test data and seem to confirm the confinement effect observed in the experiments. [Copyright &y& Elsevier]

Abstract: This paper focus on the design of a GFRP truss-like structure for dismountable bridges with maximum span of 30m. The bridge structure is composed of a deck supported by prestressed trussed beams which are mounted by assembling GFRP tubular profiles and steel joints with bearing type connections. Experimental tests were carried out on short profiles to determine their compressive strength at the connections and on two 1:2.3 reduced models of the trussed beam structure: a short 1.3m span cantilever beam and a 13.0m span simple supported beam. The main results obtained from the performed experimental tests on short profiles and on the cantilever beam are presented herein. It is shown that a non-linear behaviour can be generated on the trussed cantilever beam by decompression of tubular members and that collapses are induced by buckling of diagonal members. [Copyright &y& Elsevier]