The solid core of the earth is an iron sphere with a diameter of ~ 2,500 km, at temperature of ~5,000K and pressure of ~350 GPa. This temperature far exceeds iron's melting point at ambient pressure but it is solid because of the Clausius Clapeyron equation. The mechanical properties and microstructure of the solid core are virtually unknown because of the impossibility of reaching it. Experiments at the National Ignition Facility of Lawrence Livermore National Laboratory on iron using high-powered pulsed lasers have reproduced the pressures and temperatures in the range of the earth core, albeit at a strain rate that is many orders of magnitude higher (10^6 s^-1). This is enabled by the observation of the growth rate of Rayleigh-Taylor instabilities on the surface of iron, which are dependent on the strength. The mechanisms of plastic deformation and constitutive relationships under laser compression and at the center of the solid core are evaluated analytically and computationally, enabling tentative conclusions. Nabarro- Herring and Weertman creep mechanisms are compared with dislocation glide and PTW predictions. Support: CMEC, NIF, LLNL

This study provides an in-depth review of the electrical properties of composite materials, encompassing metals, ceramics, polymers, and nanocomposites reinforced with nanometric particles. It examines critical electrical characteristics, such as conductivity and dielectric properties, and their implications for diverse applications. The analysis highlights the significant enhancement of electrical conductivity through the incorporation of metallic nanoparticles, which establish conductive networks within polymer matrices. By exploring the interactions between composite constituents, the study elucidates the behavior of these materials under varying conditions, offering valuable insights into their performance. This comprehensive review serves as a foundation for targeted future research, facilitating detailed investigations into specific composite types and their potential limitations. Furthermore, it enriches the existing literature by providing a broad perspective on the electrical properties of composites, paving the way for advancements in fields such as electronics, biomedical devices, and environmental technologies. This work underscores the importance of understanding component interactions to drive innovation and develop novel applications for composite materials.

The Cauxi sponge, a resident of the Amazon Basin, is a freshwater sponge with impressive adaptability. Belonging to the Demospongiae class, it can be considered a natural mineral-organic composite comprising sub-millimeter spicules embedded in an organic matrix, which acts as an adhesive layer. Two types of spicules are observed in a specimen from the Guaporé River: megascleres (about 150 µm long and 20 µm in diameter) and microscleres (50 µm long and 10 µm in diameter). Electron microscopy reveals that these spicules form a homogeneous, amorphous silica structure. We report the compressive strength of the spicules, obtained from micropillars, their modulus, revealed by nanoindentation, and their fracture toughness, tested using a pre-notch micro cantilever beam. The mesoporous nature of the biogenic silica is evaluated by SAXS data, showing pore sizes around 2.3 nm. Additionally, we revealed the shell structure of Cauxi gemmules, which are reinforced by short silica spicules acting as reinforcing struts. This discovery of mesoporous structures, synthesized under ambient conditions, inspires the design of artificial lightweight protective shell structures comprised of short fibers with disk-like extremities connected by an organic matrix.

Recycling natural fibers plays a crucial role in promoting environmental sustainability by reducing waste, conserving resources, and lowering the environmental impact of textile production. Natural fibers such as cotton, wool, and linen are biodegradable, but when disposed of in landfills, they contribute to pollution and resource depletion. By recycling these materials, we not only extend the life cycle of valuable resources but also decrease the demand for virgin fiber production, which often involves intensive water, energy, and chemical use. Additionally, recycling natural fibers supports a circular economy, encouraging more responsible consumption and production practices while helping to reduce greenhouse gas emissions and textile waste accumulation. On the other hand, the reinforcement of polymer matrices with natural fibers is opening new avenues for enhancing both the environmental and economic sustainability of the polymer industry, while also broadening their applications in engineering. This study investigates the additive manufacturing of composite materials reinforced with short coffee waste shells. A range of characterizations—including scanning electron microscopy and tensile testing—are presented, along with a statistical analysis of the tensile results using Weibull distribution. By incorporating this organic waste into engineered composites, the useful life of coffee shells is extended, contributing to environmental sustainability, and offering potential socio-economic benefits at the local level. The results demonstrate that the produced filaments possess promising mechanical strength and suggest the viability of scaling up the manufacturing process.

A growing demand for research about ballistic armor shields follows the increase of violence around the world. Ultimately, different composite materials with polymeric matrices have already presented the minimum performance as an individual protection required with cheaper and lower density, such as those reinforced with natural lignocellulosic fiber (NLF). The Cyperus malaccensis, a type of sedge fiber, is already used in simple items like ropes, furniture, and paper, but has not yet been investigated as composite reinforcement for possible ballistic protection applications. Therefore, composite plates were prepared for the ballistic tests, one for each condition of 10, 20 and 30 vol% sedge fibers. Each plate has been subjected to 5 test-shots  using 7.62 mm commercial ammunition. The fibers were embedded under pressure in the epoxy resin matrix and cured at room temperature for 24 hours. The tested specimens were examined by scanning electron microscopy. Besides, analysis of variance was performed and the absorbed energy of all specimens were evaluated.

This research explores the radiological shielding performance of hybrid composites made from aramid and linen fabrics embedded in an epoxy polymer matrix, reinforced with bismuth oxide (Bi2O3), using Monte Carlo N-Particle (MCNP) simulations. The study aims to assess gamma radiation attenuation by analyzing photon flux across composite layers and energy deposition within the material. The MCNP code was utilized to simulate gamma photon interactions, investigating the effects of Bi2O3 concentration, layer thickness, and fabric arrangement. Bi2O3, known for its high atomic number and density, significantly enhances the composite’s radiation attenuation capabilities while maintaining structural integrity. The results indicate substantial reductions in photon flux and efficient energy absorption, driven by the combined properties of aramid’s mechanical strength, linen’s eco-friendliness, and Bi2O3’s superior radiation-blocking capacity. The simulations highlight how composite design influences shielding effectiveness, providing valuable insights into developing lightweight, durable materials for radiological protection in medical imaging, aerospace, and industrial applications. This work lays the groundwork for experimental validation and optimization of Bi2O3-reinforced hybrid composites, advancing the development of sustainable, high-performance solutions for radiation shielding and contributing to safer and more efficient protective technologies.

This work proposes for the first time to develop a nanocomposite from polymethyl methacrylate (PMMA) based microfibers and reduced graphene oxide (rGO), synthesized using the Solution Blow-Spinning (SBS) technique [1]. This technique allows the production of fibers with a small diameter using a thermoplastic polymer, being capable of producing microfibers on a large scale. The interest is related to the reduction of the diameter when compared to conventional fibers, as the diameter size of these materials directly affects their properties, which tend to improve as the contact surface increases, thereby improving wettability [2][3]. The use of graphene and graphene oxide as reinforcing materials in composites has attracted attention, as they tend to provide greater rigidity, strength and conductivity to the material [4]. Graphene oxide is obtained by functionalizing graphene through exfoliation, creating regions with sp2 and sp3 hybridized carbons [5], in addition to hydroxyl and epoxy functional groups. This structure improves the interaction with the polymer matrix, increasing the rigidity of the composite and making it conductive, with the advantage of reducing costs when using reduced graphene oxide (rGO). The results obtained from experimental tests of concentration and morphology through Scanning Electron Microscopy (SEM) during the development of the nanocomposite will indicate the feasibility of producing a pure PMMA nanocomposite (matrix) reinforced with rGO in powder form (filler) for applications such as conductive polymer composites via Solution Blow Spinning.

This study investigates the radiological protection capabilities of hybrid composites composed of aramid and linen fabrics embedded in an epoxy polymer matrix, reinforced with graphene oxide (GO), through Monte Carlo N-Particle (MCNP) simulations. The research focuses on evaluating the attenuation of gamma radiation by analyzing photon flux between composite layers and energy deposition within the material structure. The MCNP code was employed to model the interaction of gamma photons with the hybrid composite, considering variations in GO concentration, layer thickness, and fabric stacking configurations. The incorporation of GO enhances the mechanical and shielding properties of the composite, leveraging its high electron density and dispersion within the epoxy matrix. Results demonstrate significant photon flux reduction and optimized energy absorption, influenced by the synergistic effects of aramid’s high tensile strength, linen’s sustainability, and GO’s radiation interaction capabilities. The simulations reveal the impact of composite design on shielding efficiency, offering insights into lightweight, flexible materials for radiological protection in medical, aerospace, and industrial applications. This work establishes a foundation for experimental validation and further optimization of GO-reinforced hybrid composites, contributing to the development of sustainable and high-performance radiation shielding solutions.

A growing demand for research about ballistic armor shields follows the increase of violence around the world. Ultimately, different composite materials with polymeric matrices have already presented the minimum performance as an individual protection required with cheaper and lower density, such as those reinforced with natural lignocellulosic fiber (NLF). The Cyperus malaccensis, a type of sedge fiber, is already used in simple items like ropes, furniture, and paper, but has not yet been investigated as composite reinforcement for possible ballistic protection applications. Therefore, composite plates were prepared for the ballistic tests, based on the condition of 30 vol% alkali treated sedge fibers. A total of seven plates have been subjected to seven test-shots  using 7.62 mm commercial ammunition. The fibers were embedded under pressure in the epoxy resin matrix and cured at room temperature for 24 hours. The tested specimens were examined by scanning electron microscopy. Besides, analysis of variance (ANOVA) was performed and the absorbed energy of all specimens were evaluated, based on a confidence level of 95%.

Natural lignocellulosic fibers (NLFs) have been widely studied as sustainable alternatives to synthetic fibers, standing out for being renewable, biodegradable, economically viable and for presenting good specific mechanical properties [1-3]. In this context, the present study aimed to evaluate the flexural strength of polyester matrix composites reinforced with short jute and piassava fibers. The fibers were used in their natural form, without surface treatment, cut to a length of 15 mm, and incorporated into the matrix by manual molding (hand lay-up) using silicone molds, without the application of pressure. The specimens were produced with randomly distributed discontinuous fibers, with mass fractions adjusted to the mold volume. The bending tests indicated that the pure polyester composite presented a bending stress of 112.12 ± 17.58 MPa, while the composites reinforced with jute and piassava fibers reached 59.16 ± 8.37 MPa and 62.48 ± 5.89 MPa, respectively, representing reductions of approximately 47% and 44% in relation to the pure matrix. Fractographic analysis of the rupture surfaces revealed that the failure of the composites was predominantly governed by fiber pull-out and low interfacial adhesion between fiber and matrix, also associated with the presence of internal voids resulting from the manual molding process. These factors contributed to the reduction of the mechanical efficiency of the composites, highlighting the need for surface treatments of the fibers and improvements in processing to optimize structural performance.

Hydroxyapatite is a mineral composed of hydrated calcium phosphates. As it is the main mineral component of human bone, it is widely used in the fabrication of alloplasts for bone tissue regeneration treatments, known as scaffolds [1][2]. Scaffolds serve as a cellular matrix for the development of new bone tissue; therefore, they must have a porous structure, adequate mechanical strength, and be composed of biocompatible material [3]. To meet these criteria, additive manufacturing techniques, such as fused deposition modeling (FDM) 3D printing, are employed as an alternative for controlling structure and mechanical strength. However, if the printer operates by extruding thermoplastic material, it is necessary to synthesize polylactic acid (PLA) filament loaded with hydroxyapatite to incorporate the bioceramic into the scaffold [4]. Hydroxyapatite can be obtained through various synthesis routes or from synthetic or natural resources. In this study, hydroxyapatite was extracted from the byproduct of the Arapaima gigas fish and used to produce filaments for 3D printing. The scales were subjected to chemical treatment with NaOH and thermal treatment with sintering at 600 ºC in an oxygen-rich environment. The characterizations performed were TG, DTG, DSC, FTIR, and SEM. After these characterizations, the sample was subjected to a thermal treatment at 700 ºC, followed by the same analyses. The filaments were produced by extrusion and were loaded with 1% w/w of hydroxyapatite extracted from the scales of Arapaima gigas. The filaments were subjected to tensile testing according to ASTM C1557-20. Thermal analysis revealed that the sample sintered at 600 ºC did not undergo complete removal of organic volatiles, with mass losses of 3.6% in the range of 75 ºC – 100 ºC due to residual water; 1.1% in the range of 280 ºC – 700 ºC due to collagen residue; and 2.93% between 600 ºC – 742 ºC due to the loss of structural water from hydroxyapatite. The sample sintered at 700 ºC showed little mass loss, with a total loss of 1.68%, and a maximum degradation temperature at 619 ºC, related to the structural water present in hydroxyapatite. In both samples, FTIR analyses revealed the characteristic bands of PO₄³⁻ anions at 1091 cm⁻¹; 1022–1018 cm⁻¹; 602–563 cm⁻¹, and the presence of CO₃²⁻ ions at 1450 cm⁻¹, 1411 cm⁻¹, and 871 cm⁻¹. Scanning electron microscopy (SEM) micrographs showed that the samples sintered at 600 ºC presented agglomerates of inorganic particulates without a defined morphology. Sintering at 700 ºC promoted the growth of particulates with polygonal shapes, tending toward hexagonal formation.

Hydroxyapatite (HA), an inorganic ceramic biomaterial, presents itself as a promising and active bone substitute in this scenario, as it presents characteristics similar to the mineral apatite, found in human bones and teeth. Thus, the aim of this work is to synthesize and characterize synthetic hydroxyapatite, using chicken eggshell residue as a source of calcium. The analysis of the egg shell was carried out using X-ray Diffraction (XRD) and Fourier Transform Spectroscopy (FTIR) techniques. The characterization of the hydroxyapatite powder was performed by X-Ray Diffraction (XRD), Fourier Transform Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results for eggshell revealed the presence of absorption bands of hydroxyl groups and carbonates and phases corresponding to calcium hydroxide and calcium oxide. The HA sample showed vibration bands of hydroxyl, carbonate and phosphate groups, and hydroxyapatite and calcium oxide phases. SEM analysis indicated irregular morphological formations with dimensional variations. The EDS semiquantitatively revealed percentages of Oxygen, Phosphorus and Calcium. According to the results, type B hydroxyapatite was obtained using eggshell residue, which was also a good source of calcium in this study.

Recycling natural fibers is essential for advancing environmental sustainability, as it helps reduce waste, conserve resources, and minimize the ecological footprint of textile production. While fibers like cotton, wool, and linen are biodegradable, their disposal in landfills still contributes to pollution and the depletion of valuable materials. By recycling these fibers, we can extend their lifecycle, lessen reliance on virgin fiber production—which typically requires significant water, energy, and chemical inputs—and promote more sustainable industrial practices.

Moreover, recycling natural fibers aligns with the principles of a circular economy by encouraging responsible consumption and production, reducing greenhouse gas emissions, and limiting the accumulation of textile waste. In parallel, reinforcing polymer matrices with natural fibers is emerging as a promising approach to enhance both the environmental and economic sustainability of polymer-based products, while expanding their applicability in various engineering fields.

This study explores the fabrication of composite materials reinforced with rice husk, an agricultural byproduct. A comprehensive evaluation is provided, including scanning electron microscopy and tensile testing, alongside a statistical analysis of tensile data using the Weibull distribution. Utilizing rice husk in engineered composites not only extends the utility of this organic waste but also supports sustainability efforts and offers potential socio-economic advantages at the community level. The study presents several case examples involving both polymer and inorganic matrices, utilizing both traditional and additive manufacturing techniques.