Search Results (14)

Currently, the need for resource efficiency and CO₂ reduction is growing in industrial production, particularly in the automotive sector. To address this, the industry is focusing on lightweight components that reduce weight without compromising mechanical properties, which are essential for passenger safety. Hybrid designs offer an effective solution by combining weight reduction with improved mechanical performance and functional integration. This study focuses on a one-step manufacturing process that integrates forming and bonding of hybrid systems using compression molding. This approach reduces production time and costs compared to traditional methods. Conventional Post-Mold Assembly (PMA) processes require two separate steps to combine fiber-reinforced plastic (FRP) structures with metal components. In contrast, the novel In-Mold Assembly (IMA) process developed in this study combines forming and bonding in a single step. In the IMA process, glass-mat-reinforced thermoplastic (GMT) is simultaneously formed and bonded between two metal belts during compression molding. The GMT core provides stiffening and load transmission between the metal belts, which handle tensile and compressive stresses. This method allows to produce hybrid structures with optimized material distribution for load-bearing and functional performance. The process was validated by producing a lightweight hybrid brake pedal. Demonstrating its potential for efficient and sustainable automotive production, the developed hybrid brake pedal achieved a 35% weight reduction compared to the steel reference while maintaining mechanical performance under quasi-static loading Full article

Voids behind tunnel linings can be formed either during or after the construction phase, occurring due to inadequate backfilling, substandard workmanship, water erosion, or gravitational forces. Investigations into numerous tunnels in which collapses occurred while in operation have indicated that voids behind the liner constitute the primary contributors to these failures. Consequently, it is imperative to devise lining reinforcement strategies tailored to the specific conditions encountered in the field. Fiber-reinforced plastic (FRP) represents a viable alternative construction material that has been widely utilized in the reinforcement of concrete structures. It is essential to quantitatively assess the reinforcing effect of FRP grids when they are employed in the restoration of deteriorated tunnel linings, thereby facilitating the development of effective maintenance designs. In this study, we aimed to enhance the sensitivity analysis of the reinforcement method by evaluating the impact of voids through the analysis of bending moments and axial forces within the tunnel lining. The effects of voids based on the different locations in which they occur were explored numerically through an Elastoplast finite element analysis. The study involved simulating tunnel linings that had been reinforced with FRP grids and assessing the effects of such reinforcement in tunnels afflicted with various structural problems. Based on the outcomes of these simulations, the internal forces within the lining are scrutinized, and the efficacy of the reinforcement is appraised. Full article

Within the rapidly growing market for fiber-reinforced plastics (FRPs), conventional production processes involving molds are not cost-efficient for prototype and small series production. Therefore, new flexible forming techniques are increasingly being researched, many of which have been inspired by incremental sheet metal forming (ISF). Due to the different deformation mechanisms of woven reinforcement fibers and metal sheets, ISF is not directly applicable to FRP. Instead, shear and bending of the fibers need to be realized. Therefore, a new dieless forming process for the production of FRP supported by metal wire mesh as an auxiliary material is proposed. Two standard tools, such as hemispherical punches, are used to locally bend a reversible layup of metal wire mesh and woven reinforcement fiber fabric enclosed in a vacuum bag. Therefore, the mesh aids in introducing shear into the material due to its ability to transmit compressive in-plane forces, and it ensures that the otherwise flexible fabric maintains the intended deformation until the part is cured or solidified. Basic experiments are conducted using thermoset prepreg, woven commingled yarn fabric, and thermoplastic organo sheets, proving the feasibility of the approach. Full article

When a tsunami occurs, people can enter floating shelters and save their lives. Tsunami shelters consisting of thin-walled fiber-reinforced plastic (FRP) spherical shells have been developed and are currently in use. In this study, a novel three-layer laminated spherical tsunami shelter and its fabrication method have been proposed as an alternative to the conventional thin-walled spherical FRP tsunami shelter. First, the inner and outer layers were made of thin-walled stainless-steel spherical shells using the integral hydro-bulge-forming (IHBF) method. The inter-layers between the inner and outer layers were filled with elastic rubber to provide a laminated spherical tsunami shelter with elastic cushioning layers. After the fabrication process was developed, a laminated spherical tsunami shelter with a plate thickness of 1.0 mm, an inner spherical shell design radius of 180 mm, and an outer spherical shell design radius of 410 mm was fabricated. The shape accuracy of the process was determined. The roundness values of the inner and outer layers of the spherical shell were 0.88 and 0.85 mm, respectively. The measured radii of the actual inner and outer spherical shells were 180.50 and 209.97 mm, respectively, and the errors between the design and measured radii were 0.28% and −0.01%. In this study, acceleration sensors were attached to the inner and outer layers of the processed, laminated spherical tsunami shelter. A hammer impact load was applied to the outer layer, and the response acceleration values measured by the acceleration sensors in the inner and outer layers were compared. It was confirmed that the response acceleration value of the inner layer was 10.17% smaller than that of the outer layer. It was then verified that the spherical tsunami shelter proposed in this study has a good cushioning effect and processing performance. Full article

Concrete structures are subjected to various forms of damage in cold regions. However, the interfacial bonding properties of traditional concrete (NC) reinforced with textile-reinforced cementitious composite (TRECC) under freeze–thaw cycle damage have not been fully studied. In this paper, different control groups were obtained by adjusting the types and layers of Fiber Reinforced Plastics (FRP) in TRECC and the interfacial roughness level between TRECC and NC. After experiencing 0–300 freeze–thaw cycles, each group underwent the uniaxial tensile test, three-point bending test, and scanning electron microscope observation. The results show that FRP type in TRECC can determine the strength of specimens. After 100 freeze–thaw cycles, the ultimate tensile strength of TRECC with two different FRP types increased by 38.4% and 55.3%, respectively, compared with TRECC. Furthermore, the bond strength and resistance to freeze–thaw damage of TRECC-NC interface increased with the increase of roughness under the action of freeze–thaw cycles. After 100 freeze–thaw cycles, the bonding strength of the repair system reached the highest. Compared with 0 freeze–thaw cycles, the ultimate tensile strength of the TRECC-NC reinforcement system under low roughness and high roughness increased by 50.05% and 61.25%, respectively. Meanwhile, the internal cracks of TRECC gradually developed and penetrated, reducing the cooperative working ability between TRECC-NC. Full article

The demand for lightweight materials, such as fiber-reinforced plastics (FRP), is constantly growing. However, current FRP production mostly relies on expensive molds representing the final part geometry, which is not economical for prototyping or highly individualized products, such as in the medical or sporting goods sector. Therefore, inspired by incremental sheet metal forming, we conduct a systematic functional analysis on new processing methods for shaping woven FRP without the use of molds. Considering different material combinations, such as dry fabric with thermoset resin, thermoset prepreg, thermoplastic commingled yarn weave and organo sheets, we propose potential technical implementations of novel dieless forming techniques, making use of simple robot-guided standard tools, such as hemispherical tool tips or rollers. Feasibility of selected approaches is investigated in basic practical experiments with handheld tools. Results show that the main challenge of dieless local forming, the conservation of already formed shapes while allowing drapability of remaining areas, is best fulfilled by local impregnation, consolidation and solidification of commingled yarn fabric, as well as concurrent forming of prepreg and metal wire mesh support material. Further research is proposed to improve part quality. Full article

In this study, a lightweight fiber-reinforced plastic (FRP) helical gear was fabricated to investigate the potential application of FRP in automobile parts that require high loads and reduced noise. High-performance aramid FRP processed using the wet-laid method was used in the tooth region, and SCR420 steel was used in the inner hub region. A hot-forming system that combines rapid induction heating and water channel cooling methods was developed to reduce the cycle time. The cooling water flow conditions were analyzed to precisely control the mold temperature. Additionally, a rotating extraction system was developed to mitigate the extraction difficulty owing to the helix angle to the extraction direction. Using the innovative hot-forming system developed in this study, a helical gear without any process-induced defects was fabricated with a significantly reduced cycle time. The performance of the gear was successfully estimated using gear durability, torsional strength, and motion noise tests. The use of FRP materials offers significant potential to realize lightweight components; however, certain challenges related to their properties that may limit their application must be addressed on a case-by-case basis. Full article

In order to further improve the insulation performance of fiber reinforce plastic (FRP) materials used in electromagnetic pulse (EMP) simulators, the flashover characteristics of FRP materials with different surface roughness and groove, i.e., those who are easily achieved and have a prominent effect, are investigated in 0.1 MPa SF₆ under nanosecond pulse voltage with a rise time of 20–30 ns. The experimental results show that surfaces with different roughness have no significant influence on the flashover voltages of the FRP insulators, and both the convex grooves made of FRP and the convex grooves with nylon rings inlaid to form projections can improve the surface flashover voltage of epoxy FRP insulators under nanosecond pulse, in which the effect of the former surface is more obvious. For the insulators with convex grooves made of FRP, it is found that the root of the FRP protrusions breaks down after a number of shots with the occurrence of carbonization channels and spots, which is nonexistent for the nylon projections. Combined with the test results of surface characteristics, the surface roughness and the secondary electron emission yield (SEEY) are not key factors of flashover characteristics in SF₆ under nanosecond pulse, arguably due to the fact that the energy needed for an incident electron to ionize an SF₆ molecule is lower than that to excite two secondary electrons. Hence, the flashover performance cannot be improved by adjusting the surface roughness, and the flashover channel is principally governed by the macroscopic distribution of electrical field which can be changed by the convex groove. Breakdown phenomena of FRP protrusions indicate that the bulk insulation performance of resin FRP is weaker compared to pure resin because of its composite structure, as well as the impurities and voids introduced in the manufacturing process. The results are instructive for the design of FRP insulation structures in the compact EMP simulator. Full article

In light of climate change, fiber-reinforced plastics (FRP) are becoming increasingly important due to their lightweight construction potential. This benefit is additionally expanded on with the low cycle times, scrap rates and material costs of Sheet Moulding Compounds (SMC), making it the most often used material on the FRP market. While extensive studies regarding the recycling of SMC with unsaturated polyester-based matrices (UP-SMC) have been conducted in the past, this is not the case for vinylester-based SMC (VE-SMC). In this research, VE-SMC components were subject to a particle-recycling approach. Recyclate in the form of VE-SMC regrind was used to substitute SMC matrices during the compounding process. The dependence of the mechanical properties and failure behavior of VE-SMC containing regrind was investigated by means of microscopic and mechanical test methods for varying mass proportions of SMC regrind. Due to the addition of SMC regrind, a decreased fiber/matrix adhesion was observed. Furthermore, an increase in pore formation was observed with an increasing proportion of SMC regrind. The flexural modulus increased by 20% with a low percentage of regrind (ω_rSMC = 10 wt.%) in comparison to virgin SMC. In contrast, the tensile properties decrease (up to 30%) with the addition of SMC regrind independent of the investigated proportions of SMC regrind. Full article

Considering the characteristics of narrow underground space and energy distribution, based on blade element momentum theory, Wilson optimization model and MATLAB programming calculation results, the torsion angle and chord length of wind turbine blade under the optimized conditions were obtained. Through coordinate transformation, the data were transformed into three-dimensional form. The three-dimensional model of the blade was constructed, and the horizontal axis wind turbine blade under the underground low wind speed environment was designed. The static structural analysis and modal analysis were carried out. Structural design, optimization calculation and aerodynamic analysis were carried out for three kinds of air ducts: external convex, internal concave and linear. The results show that the velocity distribution in the throat of linear air duct is relatively uniform and the growth rate is large, so it should be preferred. When the tunnel wind speed is 4.3 m/s and the rated speed is 224 rad/s, the maximum displacement of the blade is in the blade tip area and the maximum stress is at the blade root, which is not easy to resonate. The change rate of displacement, stress and strain of blade is positively correlated with speed. The energy of blade vibration is mainly concentrated in the swing vibration of the first and second modes. With the increase in vibration mode order, the amplitude and shape of the blade gradually transition to the coupling vibration of swing, swing and torsion. The stress and strain of the blade are lower than the allowable stress and strain of glass fiber reinforced plastics (FRP), and resonance is not easy to occur in the first two steps. The blade is generally safe and meets the design requirements. Full article

Fiber optic sensors are gradually replacing electrical sensors in geotechnical applications owing to their immunity to electrical interference, durability, and cost-effectiveness. However, additional protective measures are required to prevent loss of functionality due to damage to the sensors, cables, or connection parts (splices and/or connectors) during installation and completion processes in borehole applications. We introduce two cases of installing fiber Bragg grating (FBG) strain sensors in 1 km boreholes to monitor the behavior of deep subsurface faults. We present our fiber-reinforced plastic (FRP) forming schemes to protect sensors and splices. We also present uniaxial load test and post-completion monitoring results for assessing the effects and performance of the protective measures. The uniaxial load test and post-completion monitoring show that FBG sensors are well protected by FRP forming without significant impact on sensor performance itself and that they are successfully installed in deep boreholes. In addition to summarizing our learning from experiences, we also suggest several points for consideration to improve the applicability of FBG sensors in borehole environment of the geotechnical field. Full article

The strengthening intervention strategies that exist for masonry buildings are based on the use of thin composites and are a recent activity used in structural engineering. Nowadays, mortar matrices are frequently found instead of epoxy resins, since the fiber reinforced cementitious matrix (FRCM) composites are more compatible with masonry than fiber reinforced plastic (FRP) ones. The mortar matrix in FRCM composites is not comparable to the epoxy resin, and therefore its contribution is different not only in traction but above all on the compression side. Due to its larger thickness, if compared to the epoxy resin, the impact of the mortar matrix on the flexural response of strengthened cross sections is not negligible. This paper aimed to investigate the influence of the contribution of the mortar matrix on the compression side on the flexural capacity of strengthened cross section. As such, p–m interaction domains and bending moment–curvature diagrams were evaluated to understand the influence of several mechanical properties of fiber and mortar matrices on FRCM efficiency, typical of real applications. Hence, the impact of several constitutive relationships of composites (linear and bilinear behavior) was considered for the structural analysis of the strengthened cross section. The presented results are all completely in a dimensionless form; therefore, independent of geometry and mechanical parameters can be the basis for developing standardized design and/or verification methodologies useful for the strengthening systems for masonry elements. Full article

When fiber-reinforced plastic (FRP) components are designed, it is very important to ensure that textiles are formed into complex 3D geometries without folds, and that the reinforcing structure is oriented appropriately. Most research in this context is focused on finite element (FE) forming simulations and the required characterization of textile reinforcements. However, the early stage of the design of FRPs, where kinematic draping simulations are used, is barely considered. In particular, the need for a critical shear angle for the execution and evaluation of kinematic draping simulations is often neglected. This paper presents an extended picture frame test stand with an optical device recording shear-induced deformations with the help of a laser line emitter. Associated hardware and software for detecting and quantifying the fold formation during a picture frame test were developed. With the additional recorded information, a material-specific critical shear angle can be determined, material behaviors can be compared, and FE-based simulation methods can be evaluated. This innovative test stand and the associated software tools will help engineers to decide on suitable materials and improve transparency in the early stages of the design process. Full article

A self-referencing, intensity-based fiber optic sensor (FOS) is proposed and demonstrated. The theoretical analysis for the proposed design is given, and the validity of the theoretical analysis is confirmed via experiments. We define the measurement parameter, X, and the calibration factor, β, to find the transfer function, , of the intensity-based FOS head. The self-referencing and multipoint sensing characteristics of the proposed system are validated by showing the measured and relative error versus the optical power attenuation of the sensor head for four cases: optical source fluctuation, various remote sensing point distances, fiber Bragg gratings (FBGs) with different characteristics, and multiple sensor heads with cascade and/or parallel forms. The power-budget analysis and limitations of the measurement rates are discussed, and the measurement results of fiber-reinforced plastic (FRP) coupon strain using the proposed FOS are given as an actual measurement. The proposed FOS has several benefits, including a self-referencing characteristic, the flexibility to determine FBGs, and a simple structure in terms of the number of devices and measuring procedure. Full article