Effect of Fibrillated Cellulose on Lime Pastes and Mortars

The use of nanocellulose in traditional lime-based mortars is a promising solution for green buildings in the frame of limiting the CO2 emissions resulting from Portland Cement production. The influence of the fibrillated cellulose (FC) on lime pastes and lime-based mortars was studied incorporating FC at dosages of 0%, 0.1%, 0.2% and 0.3wt% by weight of binder. The lime pastes were subjected to thermal and nitrogen gas sorption analyses to understand if FC affects the formation of hydraulic compounds and the mesoporosities volume and distribution. The setting and early hydration of the mortars were studied with isothermal calorimetry. The mechanical performances were investigated with compressive and three-point-bending tests. Furthermore, fragments resulting from the mechanical tests were microscopically studied to understand the reinforcement mechanism of the fibres. It was found that 0.3wt% of FC enhances the flexural and compressive strengths respectively by 57% and 44% while the crack propagation after the material failure is not affected.

Experimental study on mechanical behavior of orthotropic steel deck with adhesively bonded rigid pavement

The steel deck with rigid pavement has a lower risk of fatigue failure owing to the enhanced local rigidity. A reliable connection of steel plate and pavement and a convenient construction are critical concerns for this deck type. To seek a new application meeting the aforementioned requirements, this paper proposed a steel deck with adhesively bonded rigid pavement cast by non-reinforced ultra-high performance concrete (UHPC). To study the constructability and flexural properties of this deck type in a bridge deck system, four specimens including two with adhesively bonded connection and two reference ones with shear stud connection were fabricated and experimentally investigated by positive and negative bending tests. In addition, a simplified pretreatment of steel substrate was conducted before the application of epoxy resin to simulate the low quality of on-site construction. Experimental results indicate that the shear strength of the bonding connection with simplified steel pretreatment could decrease to half of that with strict preparation. Bending tests demonstrate that the adhesive bonding provides a more rigid connection between steel and concrete than shear studs did. The bonding failure load was 1.5 times the U-rib yielding load, indicating a high positive bending-carrying capacity of the deck. The adhesive provides better crack resistance than shear studs in negative bending. From a perspective on the bending behavior in the deck system, the adhesive bonding was reliable to obtain high bending capacities to resist actual vehicle loads. Besides, the non-uniform shrinkage of non-reinforced UHPC pavement can cause a 30% reduction of cracking strength.

Expanded (Black) Cork for the Development of an Eco-Friendly Surfboard: Environmental Impact and Mechanical Properties

Based on global needs for sustainable development, finding new sustainable materials that can replace oil-based ones for mass products is crucial nowadays. This paper focuses on employing an expanded cork-based composite to produce a surfboard. To evaluate the mechanical properties, uniaxial tensile and compression tests were performed on the skin and core materials, respectively. Bending tests were performed on the entire representative composite structure. Numerical models of the tests were arranged and validated from experimental results. From that, a surfboard prototype model was used to simulate some experimental conditions, permitting us to draw promising conclusions. An actual prototype was also produced. It was found that expanded cork performs very well when sandwiched between wood and polyester resin/glass fibre, being able to hold substantial loads and at the same time reduce weight and the environmental footprint of the composite by 62.8%. It can be concluded that expanded cork is an excellent candidate to replace oil-based foams in surfboard manufacturing. Despite a slight increase in weight, this sustainable material aligns with all the philosophies of surf practice worldwide.

Hybrid Finite-Discrete Element Modelling of Various Rock Fracture Modes during Three Conventional Bending Tests

The numerical techniques for modelling the rock fracture have been briefly reviewed. A hybrid finite-discrete element method (HFDEM) is proposed to simulate various fracture types of rock. A fracture model is implemented in the HFDEM for simulation of the three main fracture types. In addition, the influence of the strain rate is considered during the HFDEM modelling rock behavior. Then, two typical rock mechanism tests are employed to calibrate the HFDEM. The proposed method has well modelled the rock fracture processes and can obtain reasonable stress distribution and force–displacement curves. After that, the HFDEM is used to model three convention bending tests. The obtained rock fracture processes indicates that the HFDEM can simulate various fracture types. The obtained rock strengths and fracture toughness indicate that the HFDEM can reflect the influence of the strain rate. It is concluded that the HFDEM can model the entire and complete rock fracture process during the three convention bending tests, and it also can capture the rock’s behavior on the strain rate.

Experimental and numerical investigation on bending and compressive behavior of carbon-epoxy sandwich panel with novel M-shaped core

Present paper has experimentally and numerically investigated the mechanical behavior of composite sandwich panel with novel M-shaped lattice core subjected to three-point bending and compressive loads. For this purpose, a composite sandwich panel with M-shaped core made of carbon fiber has been fabricated in this experiment. In order to fabricate the sandwich panels, the vacuum assisted resin transfer molding (VARTM) has been used to achieve a laminate without any fault. Afterward, polyurethane foam with density of 80 kg/m3 has been injected into the core of the sandwich panel. Then, a unique design was presented to sandwich panel cores. The study of force-displacement curves obtained from sandwich panel compression and three-point bending tests, showed that an optimum mechanical strength with a considerable lightweight. It should be noted that the experimental data was compared to numerical simulation in ABAQUS software. According to the results, polyurethane foam has improved the flexural strength of sandwich panels by 14% while this improvement for compressive strength is equal to 23%. As well as, it turned out that numerical results are in good agreement with experimental ones and make it possible to use simulation instead of time-consuming experimental procedures for design and analysis.

A study of tensile and bending properties of 3D-printed biocompatible materials used in dental appliances

In the last years, a large number of new biocompatible materials for 3D printers have emerged. Due to their recent appearance and rapid growth, there is little information about their mechanical properties. The design and manufacturing of oral appliances made with 3D printing technologies require knowledge of the mechanical properties of the biocompatible material used to achieve optimal performance for each application. This paper focuses on analysing the mechanical behaviour of a wide range of biocompatible materials using different additive manufacturing technologies. To this end, tensile and bending tests on different types of recent biocompatible materials used with 3D printers were conducted to evaluate the influence of the material, 3D printing technology, and printing orientation on the fragile/ductile behaviour of the manufactured devices. A test bench was used to perform tensile tests according to ASTM D638 and bending tests according to ISO 178. The specimens were manufactured with nine different materials and five manufacturing technologies. Furthermore, specimens were created with different printing technologies, biocompatible materials, and printing orientations. The maximum allowable stress, rupture stress, flexural modulus, and deformation in each of the tested specimens were recorded. Results suggest that specimens manufactured with Stereolithography (SLA) and milling (polymethyl methacrylate PMMA) achieved high maximum allowable and rupture stress values. It was also observed that Polyjet printing and Selective Laser Sintering technologies led to load–displacement curves with low maximum stress and high deformation values. Specimens manufactured with Digital Light Processing technology showed intermediate and homogeneous performance. Finally, it was observed that the printing direction significantly influences the mechanical properties of the manufactured specimens in some cases.