Effect of Reinforcement Fiber Arrangement on Thermal and Mechanical Properties of High Silica/Phenolic Resin Insulation Layer

The failure of the high silica/phenolic resin insulation layer under extreme thermal conditions has become an important reason for the trouble of solid rocket motors. A great number of studies have shown that the arrangement of reinforcement fibers is a significant factor in the failure of fiber-reinforced plastic. In this paper, the thermal and mechanical properties of the high silica/phenolic resin insulation layer with different arrangements were analyzed, and the causal relationship between the failure of the insulation layer and the arrangement of reinforcement fibers was given. Two types of heat-insulating layers with strong arrangement and weak arrangement were designed. After the SRM firing test, it is concluded that the essential reason for the failure of the insulation layer is the strength anisotropy caused by the weak arrangement of reinforcement fibers. Besides, the reinforcement fibers of strong arrangement are distributed in all directions, which compensates for the axial strength defects of the weakly arranged insulation layer.

3D printing as an automated manufacturing method for a carbon fiber-reinforced cementitious composite with outstanding flexural strength (105 N/mm2)

As research interest in the additive manufacturing of cementitious materials for structural uses has been continuously increasing, the question of how to incorporate tensile reinforcement in an automated process has gained further importance. Our research describes a carbon fiber-reinforced cementitious composite produced by common extrusion techniques applied in 3D printing as a means to effectively control fiber alignment. Optimization of the mixture design and consistency allows for admixing up to 3 vol.-% chopped carbon fibers, leading to specimens that can reach a flexural strength exceeding 100 N/mm2 without the addition of further continuous reinforcement. Fiber integrity during the process was checked using optical microscopy. Analysis of the microstructure shows that approximately 70% of the fibers are aligned within ± 5° of a preferential direction. Micromechanical single-fiber push-out tests confirm an interfacial fracture toughness typical for strain-hardening systems. The first insights into a ‘lost formwork’ approach commonly employed in 3D printing show that the reinforcement remains effective even when combined with nonreinforced mortar.

Improvement of Buckling Behavior of Composite Plates Reinforced with Hybrids Nanomaterials Additives

Modifying buckling behavior of the composite structure has been investigated in the recent few years with different reinforcement fiber and powder materials and nanomaterials. It can be seen from previous studies that the addition of nanomaterials leads to a significant modification in the buckling behavior of structure by using a low mount of nanomaterials. In this work, reinforcement of composite materials using two types of nanomaterials together, SiO2 and Al2O3 nanomaterials, to modify the buckling behavior for plate structure is studied. Therefore, the investigation was done experimentally and numerically. The experimental work is performed by manufacturing composite plates with various weight fractions with the nanoeffect, and then their mechanical properties and buckling characterization were evaluated. The numerical work was done using the finite element method to estimate the plate structure’s buckling behavior with various nanomaterials effects. A comparison between the experimental and the numerical results for plate buckling behavior is expressed, showing that the discrepancy of the results was not more than 12.56%. Finally, the results showed that the buckling behavior for a reinforced plate was improved by 35% when two types of nanomaterials were used together.

Study of Whiskers to be Used in Composite Materials

Rapid expansion of technologies poses higher requirements to structural materials and items made of them. Conventional materials are being replaced by composite materials (composites). Different additives enhancing the properties of initial materials are used as reinforcement fibers of composites. Utilization of micro-and nanosize particles for production of present-day materials is paid much attention to. Whiskers are among such materials. These crystals have high strength, high chemical and temperature resistance. But for rational utilization of whickers of different chemical composition in composite materials one should know their physical and chemical properties. Objectives of the paper: to study physical and chemical properties of whiskers in different compounds, their composition and structure; to prove experimentally the feasibility of utilizing whiskers as a reinforcement fiber of composite materials. Object of study: specimens of whiskers of silicon nitride (Si3N4), aluminum oxide (Al2O3), aluminum nitride (AlN), and mullite (Al6Si2O13). Methods of investigation: thermal study of specimens, study of mechanical properties and chemical strength, and IR-spectroscopy. Results of study: specimens of whiskers have been studied and their mechanical properties have been tabulated for comparison. Extensive thermal investigation was followed by deduction of regularities and identification of chemical properties of whiskers. IR-spectra of whiskers have been studied and conclusions on molecular composition and on presence of impurities in some whiskers have been made.

Response Surface Method Analysis of Chemically Stabilized Fiber-Reinforced Soil

One of the significant issues persisting in the study of soil stabilization is the establishment of the optimum proportions of the quantity of stabilizer to be added to the soil. Determining optimum solutions or the most feasible remedies for the utilization of stabilizing products in terms of their dose rates has become a significant concern in major civil engineering design projects. Using the response surface methodology, this study primarily focused on investigating the optimal levels of reinforcement fiber length (FL), fiber dosage (FD), and curing time (CT) for geotechnical parameters of stabilized soil. To realize this objective, an experimental study was undertaken on the California bearing ratio (CBR) and unconfined compressive strength (UCS). Hydraulic conductivity (HC) tests were also performed, with stabilizer proportions of 6–12 mm for the FL and 0.2–0.6% for the FD calculated for the total dry weight of soil and 6% lime (total weight of dry soil). The curing times used for testing were 0, 7, and 14 days for the CBR tests; 60, 210, and 360 days for the UCS tests; and 7, 17, and 28 days for the HC tests. All practical experiments were conducted with experimental techniques using stabilizer proportions and curing times. The FL, FD, CT, CBR, UCS, and HC response factors were determined using the central composite design. The results point toward a statistically significant model constructed (p ≤ 0.05) using the analysis of variance. The results from this optimization procedure show that the optimal values for the FL, FD, and CT were 11.1 mm, 0.5%, and 13.2 days, respectively, as these provided the maximum values for the CBR; 11.7 mm for the FL, 0.3% for the FD, and 160 days for the CT corresponded to the maximum values for the UCS; and 10.5 mm for the FL, 0.5% for the FD, and 15 days for the CT led to the minimum value for the HC. In practice, the suggested values may be useful for experiments, especially for preliminary assessments prior to stabilization.

Machine Vision for As-Built Modeling of Complex Draped Composite Structures

The transition in the use of fiber composite structures from special applications to application in the mass market is accompanied by high demands in quality assurance. The consequential costs of unclear process design, unknown fiber orientations, and uncertainty regarding the effects of any fiber angle deviations can lead to market considerations (higher costs/time for development) in mass production that advise against the use of fiber composites, despite their superiority compared with conservative materials. Active monitoring of the deposited reinforcement layers and an evaluation of the real fiber orientation can form the basis of a robust industrial use of fiber composites by a first-time right production that is able to reduce the process variability. This paper describes the application of an image analysis system to provide both geometric topology and local reinforcement fiber orientation feedback to a finite-element (FE) model. The application during an industrial composite part production is described, and the possibilities of using it for the improvement of the lightweight character, the reduction of rejects, and the realization of a quality management system are shown. The determined component data are made directly available for use in numerical simulations and, thus, they serve as a non-destructive evaluation of the components under real conditions in which all production-dependent influences that affect the fiber orientation are incorporated.

Experimental Studies of Fiber-Reinforced Concrete Prisms Exposed to High Temperatures

Fiber-reinforced concretes are varieties of composite materials. Such materials are commonly used nowadays. Concrete is fiber-reinforced using various fibrous materials, or fibers, which are evenly distributed over the volume of the concrete matrix and simultaneously provide its 3D reinforcement. Fiber-reinforced concrete has better stress-related strength characteristics than ordinary concrete. Since building structures must meet both the strength, rigidity and stability requirements, and the fire safety requirements, then for the extensive use of fiber-reinforced concrete structures, not only the external load design, but also temperature effect design should be conducted in the design phase. The strength and strain characteristics of fiber concrete exposed to high temperatures must be known for this purpose. In view of this, three series of prisms were manufactured and tested: the first series contained no fiber at all (control prisms), the second series contained basalt fiber, and the third series contained steel fiber. The test results showed that adding fibers improves the mechanical characteristics of fiber-reinforced concrete samples under specified conditions.

Effect of Basalt Fibers for Reinforcing Resin-Based Brake Composites

Basalt fiber is an eco-friendly reinforcement fiber in fabricating polymer composites with high specific mechanical physicochemical, biodegradable, and wear resistant properties. This article firstly introduces the composition, morphology, functional group, and thermostability of basalt fibers. Subsequently, friction composites based on a newly designed formulation were fabricated with different content basalt fibers. According to the Chinese National Standard, the physical and mechanical properties and tribological performance of the friction composites were characterized and evaluated. Extension evaluation based on extenics theory was developed to evaluate the relationships between the coefficient of friction and content of basalt fiber. Furthermore, the possible mechanism of basalt fiber reinforced friction composites was proposed.

Fabrication, Characterization and Drilling Operation of Natural Fiber Reinforced Hybrid Composite With Filler (Fly-Ash/Graphene)

The aim of the work is to investigate mechanical properties and machining (drilling) behaviour glass-sisal-epoxy hybrid composite (GSEHC) with filler as fly-ash and graphene. Hybrid composites are fabricated by hand lay-up technique using Eglass and sisal as reinforcement fiber and epoxy as binder. Mechanical and physical properties like tensile, bending, impact strength, hardness, density and water absorption percentage are examined. The interfacial properties, internal cracks and internal structure of fractured are observed using Scanning Electron Microscope (SEM). Further drilling operation on the fabricated Hybrid composite was carried by varying the spindle speed as 600 rpm, 900 rpm, 1200 rpm to observe suitable drilling speed to carry the circularity test and delamination factors.