Materials

Carbon fiber-reinforced resin matrix composites (CFRC) are extensively used in aerospace, automotive manufacturing, and sports equipment. However, the brittle nature of the resin matrix causes CFRC to exhibit severe vibrations and noise under dry friction conditions. Enhancing the intrinsic damping properties of the resin matrix serves as a fundamental and effective strategy to mitigate vibration and noise radiation in composite components. This study systematically investigates high-temperature co-curing damping composites using co-curing technology, aiming to improve the mechanical performance and damping characteristics of traditional fiber-reinforced epoxy resin composites. A novel carbon fiber-reinforced terminal carboxyl nitrile epoxy pre-polymer composite material demonstrates both stable chemical properties and excellent high-temperature resistance. Through formulation adjustments, the curing temperature and time of epoxy resin are matched with those of the terminal carboxyl nitrile epoxy pre-polymer. The performance of epoxy carbon fiber composites was evaluated through tensile tests, flexural tests, impact tests, infrared spectroscopy, thermogravimetric analysis, dynamic mechanical analysis, scanning electron microscopy, and X-ray diffraction. Results show that blending epoxy resin with terminal carboxyl nitrile liquid rubber enhances energy dissipation by increasing intermolecular friction and hydrogen bonding interactions. The damping ratio of epoxy resin-based carbon fiber composites reaches as high as 1.67%. Tensile strength, flexural strength, and impact strength reach 1968 MPa, 1343 MPa, and 127 kJ/m², respectively. The addition of terminal carboxylated nitrile liquid rubber facilitates the formation of continuous friction membranes, enhancing friction stability. Tensile tests demonstrate that carbon fiber composites containing 25% terminal carboxylated nitrile liquid rubber outperforms other formulations. As evidenced by impact tests, the performance of the prepared composites is superior to that of other configurations. Dynamic mechanical analysis indicates that the 25% rubber-containing composites exhibit enhanced damping characteristics and higher loss modulus. Experimental results confirm that this study advances the development of functional composites for vibration reduction and noise control applications.

Magnesium phosphate cement (MPC) is widely used in rapid repair applications due to its fast setting, high early strength, and high-temperature resistance. However, the high cost of magnesium oxide (MgO) and the rapid hydration reaction make it challenging to control the setting time. In this study, steel slag powder (SSP) and ground granulated blast furnace slag (GGBS) were incorporated to partially replace MgO. The reactivity of SSP and GGBS was enhanced by an alkaline activator, promoting the dissolution of their glassy phases, which facilitated the formation of C-(A)-S-H gels and improved the performance of MPC. Experimental methods, including compressive strength testing, water resistance measurements, X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), mercury intrusion porosimetry (MIP), and thermogravimetric analysis (TG), were used to evaluate the 28-day compressive strength and the microstructural characteristics of the modified MPC. When both SSP and GGBS were incorporated at 10 wt.%, the modified MPC achieved a 7-day compressive strength of 37.2 MPa, with the 28-day strength increasing to 50.2 MPa. The addition of an alkali activator with a modulus of 1.3 significantly boosted the 28-day strength to 62.3 MPa, while maintaining high flowability (215 mm). Microscopic characterization revealed that C₂S and C₃S in SSP undergo continuous hydration under alkaline conditions, while reactive silica-aluminum in GGBS reacted with phosphate to form a water-resistant C-(A)-S-H gel phase, optimizing the pore structure of MPC. This study provides a novel approach to developing low-cost, high-durability modified MPC with improved performance.

Currently, foam concrete is a prevalent energy-efficient building material, which is applicable for multiple purposes in a wide variety of buildings and structures. Improving the environmental performance of foam concrete and reducing its production costs through the use of industrial waste is a relevant and promising area. The goal of this study is to create innovative foam concrete (FC) mixtures using industrial waste, focusing on their environmentally friendly and energy-efficient properties for structural and thermal insulation purposes. The production of FC involved industrial waste products like fly ash (FA) and microsilica (MS). Nanosilica (NS) was used as an additional modifying additive. The study experimentally investigated the impact of the proposed formulation and process solutions on FC’s density, compressive strength (CS), and thermal conductivity (TC). The most effective FC modification parameters were identified for FA, MS, and NS. The best combination of 15% FA, 6% MS, and 0.4% NS produces environmentally friendly FC with improved properties: a density of 1142 kg/m³ and a TC of 0.268 W/m×°C, which are 3.8% and 15.2% lower than the control composition, respectively, and a CS of 15.1 MPa, which is 46.6% higher than the control value. Scanning Electron Microscopy (SEM) analysis validates that incorporating pozzolanic additives FA, MS, and NS into the FC composition fosters the development of more robust interpore partitions. This is due to the generation of a significant quantity of supplementary calcium hydrosilicates and a more homogenous pore structure. The structural quality factor of FC with 15% FA, 6% MS, and 0.4% NS increases to 52.4%. The structural and thermal insulation of FCs developed in this study are environmentally friendly building materials with reduced environmental impact and improved performance properties.