Biomimetic Use of Food-Waste Sources of Calcium Carbonate and Phosphate for Sustainable Materials-A Review.

Natural and renewable sources of calcium carbonate (CaCO3), also referred to as "biogenic" sources, are being increasingly investigated, as they are generated from a number of waste sources, in particular those from the food industry. The first and obvious application of biogenic calcium carbonate is in the production of cement, where CaCO3 represents the raw material for clinker. Overtime, other more added-value applications have been developed in the filling and modification of the properties of polymer composites, or in the development of biomaterials, where it is possible to transform calcium carbonate into calcium phosphate for the substitution of natural hydroxyapatite. In the majority of cases, the biological structure that is used for obtaining calcium carbonate is reduced to a powder, in which instance the granulometry distribution and the shape of the fragments represent a factor capable of influencing the effect of addition. As a result of this consideration, a number of studies also reflect on the specific characteristics of the different sources of the calcium carbonate obtained, while also referring to the species-dependent biological self-assembly process, which can be defined as a more "biomimetic" approach. In particular, a number of case studies are investigated in more depth, more specifically those involving snail shells, clam shells, mussel shells, oyster shells, eggshells, and cuttlefish bones.

Using Thermomechanical Properties to Reassess Particles' Dispersion in Nanostructured Polymers: Size vs. Content.

Nanoparticle-filled polymers (i.e., nanocomposites) can exhibit characteristics unattainable by the unfilled polymer, making them attractive to engineer structural composites. However, the transition of particulate fillers from the micron to the nanoscale requires a comprehensive understanding of how particle downsizing influences molecular interactions and organization across multiple length scales, ranging from chemical bonding to microstructural evolution. This work outlines the advancements described in the literature that have become relevant and have shaped today's understanding of the processing-structure-property relationships in polymer nanocomposites. The main inorganic and organic particles that have been incorporated into polymers are examined first. The commonly practiced methods for nanoparticle incorporation are then highlighted. The development in mechanical properties-such as tensile strength, storage modulus and glass transition temperature-in the selected epoxy matrix nanocomposites described in the literature was specifically reviewed and discussed. The significant effect of particle content, dispersion, size, and mean free path on thermomechanical properties, commonly expressed as a function of weight percentage (wt.%) of added particles, was found to be better explained as a function of particle crowding (number of particles and distance among them). From this work, it was possible to conclude that the dramatic effect of particle size for the same tiny amount of very small and well-dispersed particles brings evidence that particle size and the particle weight content should be downscaled together.

Dealing with the Effect of Air in Fluid Structure Interaction by Coupled SPH-FEM Methods.

Smoothed particle hydrodynamics (SPH) and the finite element method (FEM) are often combined with the scope to model the interaction between structures and the surrounding fluids (FSI). There is the case, for instance, of aircrafts crashing on water or speedboats slamming into waves. Due to the high computational complexity, the influence of air is often neglected, limiting the analysis to the interaction between structure and water. On the contrary, this work aims to specifically investigate the effect of air when merged inside the fluid-structure interaction (FSI) computational models. Measures from experiments were used as a basis to validate estimations comparing results from models that include or exclude the presence of air. Outcomes generally showed a great correlation between simulation and experiments, with marginal differences in terms of accelerations, especially during the first phase of impact and considering the presence of air in the model.

Dealing with Nap-Core Sandwich Composites: How to Predict the Effect of Symmetry.

The behavior of nap-core sandwiches was investigated with a special focus on the effect of symmetry in nap cores. A nap-core is, in general terms, a 3D-formed hollow structure made of knitted textile impregnated by a thermosetting resin. The molding process determines if the nap-core is double-sided (symmetric) or single-sided. The sandwich with nap-core owns various remarkable properties of a novel lightweight material, but the nap-core's complex structure makes the prediction of these properties a difficult task. While the analysis of a single-sided nap-core sandwich has been presented by the authors before, this study is focused on the simulation of symmetric nap-core sandwich. Overall, performance of the structure is examined with respect to several loading conditions. The simulation approach invokes a typical homogenization scheme to find the engineering properties of the nap-core's fabric with least computational time and memory resources. Results from experiments and simulations exhibit a good compatibility, which prove the fitness of the modeling method.

Structural Design and Manufacturing of a Cruiser Class Solar Vehicle.

Cruisers are multi-occupant solar vehicles that are conceived to compete in long-range (over 3,000 km) solar races based on the best compromise between the energy consumption and the payload. They must comply to the race's rules regarding the overall dimensions, the solar panel size, functionality, and safety and structural requirements, while the shape, the materials, the powertrain, and the mechanics are considered at the discretion of the designer. In this work, the most relevant aspects of the structural design process of a full-carbon fiber-reinforced plastic solar vehicle are detailed. In particular, the protocols used for the design of the lamination sequence of the chassis, the leaf springs structural analysis, and the crash test numerical simulation of the vehicle, including the safety cage, are described. The complexity of the design methodology of fiber-reinforced composite structures is compensated by the possibility of tailoring their mechanical characteristics and optimizing the overall weight of the car.

Mechanical Characterization of Gres Porcelain and Low-Velocity Impact Numerical Modeling.

The current investigation was conducted on gres porcelain stoneware, a robust, impermeable and aesthetically pleasing type of ceramic mainly used for flooring, characterizing its resistance to bending and low-velocity impact, both representative efforts to which flooring tiles are constantly subjected as a consequence of the fall of objects and microsubsidences. The mechanical characterization was made through experimental tests following an adapted low-velocity impact testing routine, and the model was by validated numerical simulation through the explicit code software LS-DYNA based on the Johnson⁻Holmquist constitutive material model. Specimens were tested before and after an annealing cycle industrially used to allow porcelain folding. The thermal treatment demonstrated to infer a decrease in mechanical resistance on the material, understood as a consequence of its elevated maximum temperature and fast cooling rate. The numerical model calibrated successfully allows predicting the behavior of gres porcelain before and after annealing against low-velocity impact.