Search Results (33)

This study presents the development and mechanical characterization of a full-scale helmet manufactured from a polyester matrix composite reinforced with woven jute fabric using vacuum infusion. Laminates with two and four reinforcement layers were produced and assembled using four joining configurations: seamless, stitched, bonded, and hybrid (bonded + stitched). Tensile tests were performed according to ASTM D3039, while frontal and lateral compression tests followed ABNT NBR 7471, aiming to evaluate the influence of laminate thickness and joining strategy on mechanical performance. In tension, the seamless configuration reached maximum loads of 0.80 kN (two layers) and 1.60 kN (four layers), while the hybrid configuration achieved 0.79 kN and 1.43 kN, respectively. Stitched and bonded joints showed lower strength. Under compression, increasing the laminate thickness from two to four layers reduced frontal elongation from 15.09 mm to 9.97 mm and lateral elongation from 13.73 mm to 7.24 mm, corresponding to stiffness gains of 50.3% and 87.3%, respectively. Statistical analysis (ANOVA/Tukey, α = 0.05) confirmed significant effects of thickness and joint configuration. Although vacuum infusion is a well-established process, the novelty of this work lies in its application to a full-scale natural-fiber helmet, combined with a systematic evaluation of joining strategies and a direct correlation between standardized tensile behavior and structural compression performance. The four-layer hybrid laminate exhibited the best balance between strength, stiffness, and deformation capacity. Full article

Modern automotive design has increasingly embraced plastics for bumper construction; however, it can lead to material degradation. To overcome these limitations, the automotive industry is turning to fiber–resin material, namely carbon–epoxy composites. Our research focuses on determining the effects of fiber orientation and angle alignment on the structural stress of the car bumper, examining the hybrid material (carbon–epoxy reinforced by CFRP) in static structural tests, and performing dynamic impact tests at various speeds, applying the Tsai–Wu criterion as a basic failure model. However, Tsai–Wu’s failure in numerical analysis highlights the limitation of not being able to experimentally distinguish between failure modes and their interaction coefficients. To address this issue, we employ ANSYS^® 2024 R1 with a Fortran program, which enables more accurate estimation of failure behavior, resulting in an average error of 13.19%. To identify research gaps, machine learning (ML) plays a vital role in predicting parameter values and assessing data normality using various algorithms. By combining ML and FEA simulations, the result shows strong data performance. Bridging from 2 mm mesh sizing of 50% carbon–epoxy woven/50% CFRP laminate in 6 mm thickness at 0° orientation shows the most distributed shear stresses and deformation, which converged toward stable values. For comprehensive research, total deformation was included in ML analysis as a second target to build a multivariate analysis. Overall, Random Forest (RF) is the best-performing model, indicating superior robustness for modeling shear stress and total deformation. Full article

This study quantifies how pressurized water immersion alters the reciprocating sliding behavior of glass and Kevlar woven fabric-reinforced polymer hybrid composite laminates. Specimens were immersed in deionized water at 10 bar and 25 °C for 0, 7, 14, and 21 days, then tested against a 6 mm 100Cr6 steel ball at 20 N under four regimes that combine 1 or 2 Hz with 10 m or 20 m total sliding. Water uptake rose from 0 to 8.54% by day 21 and followed a short-time Fickian square root of time trend, indicating diffusion-controlled sorption. The coefficient of friction exhibited a robust nonmonotonic response with a pronounced minimum at 14 days that was typically 20 to 40% lower than the unaged reference across frequencies and distances, while 7 days produced a partial decrease and 21 days trended upward. Three-dimensional profilometry showed progressive widening and deepening of wear tracks with immersion, for example, at 1 Hz and 10 m width increased from about 1596 to about 2050 to 2101 μm and depth from about 128 to about 184 to 185 μm, with a transient narrowing at 2 Hz after 7 days. Scanning electron microscopy corroborated a transition from mild plowing to matrix plasticization with fiber–matrix debonding and debris compaction. Beyond geometric wear metrics, this study re-processed the existing profilometry and COF records to derive a moisture-dependent mechanistic approach. Moisture uptake up to 8.54% reorganizes the third body at the interface so that friction drops markedly at 14 days (typically 20–40% below the unaged state), while concurrent matrix plasticization and interface weakening enlarge the wear cross-section extracted from the same 3D maps, decoupling friction from damage width/depth under wet conditioning. Factorial analysis ranked immersion time as the dominant driver of damage for width and depth with frequency as a secondary factor and sliding distance as a minor factor, highlighting immersion-controlled tribological design windows for marine and humid service. Full article

Hybrid woven composite materials and structures have important application value in modern engineering because of their high specific stiffness, specific strength and excellent impact resistance. The mechanical properties of carbon/aramid fiber hybrid woven composite laminates under repeated low-velocity impacts were studied in this paper. This study aims to understand the behavior of these materials under repeated impact conditions and to evaluate their damage resistance and failure mechanisms. The materials and methods used are introduced in detail, including the preparation of samples, the experimental apparatus for impact testing, and the methods of damage assessment and data analysis. The experimental setup simulated real impact scenarios and followed procedures to collect and analyze data. The low-velocity impact tests were carried out in accordance with ASTM D7136 test standard. The experimental results show that with the increase in impact energy, the damage of laminates includes delamination, matrix cracking and fiber fracture. The damage threshold and damage propagation rate are affected by the type of fiber used and its lay-up direction in the composite. Compared with (0,90)₁₂ laminates, [(0,90)/(±45)]_3s laminates show more obvious damage expansion, which highlights the importance of fiber orientation in the impact durability design of laminates. The results can be used to design and optimize the structure of hybrid woven composite laminates. Full article

Polymer matrix composites have been used extensively in the aerospace and automotive industries. Nevertheless, the growing demand for composites raises concerns about the thermal stability, cost, and environmental impacts of synthetic fillers like graphene and carbon nanotubes. Hence, this study investigates the possibility of enhancing the thermomechanical properties of polymer composites through the incorporation of agricultural waste as fillers. Particles from walnut, coffee, and coconut shells were used as fillers to create particulate composites. Bio-based composites with 10 to 30 wt.% filler were created by sifting these particles into various mesh sizes and dispersing them in an epoxy matrix. In comparison to the pure polymer, DSC results indicated that the inclusion of 50 mesh 30 wt.% agricultural waste fillers increased the glass transition temperature by 8.5%, from 55.6 °C to 60.33 °C. Also, the TGA data showed improved thermal stability. Subsequently, the agricultural wastes were employed as reinforcement for laminated composites containing woven glass fiber with a 50% fiber volume fraction, eight plies, and varying particle filler weight percentages from 0% to 6% with respect to the laminated composite. The hybrid laminated composite demonstrated improved impact resistance of 142% in low-velocity impact testing. These results demonstrate that fillers made of agricultural wastes can enhance the thermomechanical properties of sustainable composites, creating new environmentally friendly prospects for the automotive and aerospace industries. Full article

The behaviors of hybrid and non-hybrid woven composite laminates with different stacking sequences under quasi-static indentation (QSI) and compression after indentation (CAI) were investigated in this paper. A comparative experimental and numerical study was conducted to find whether the hybridization exhibits better performance, and a focus was given to the mechanisms behind it. A C-scan ultrasonic imaging system and a digital microscope to assess the visibility of the damage and penetration resistance were employed for specimens after QSI. For CAI analysis, digital image correlation (DIC) was applied. Results show that glass–carbon hybrid woven laminates ([(±45)_g/(0,90)_c]_4s) exhibit 4.31% greater load bearing efficiency, 4.45% higher residual compressive strength, and 6.35% less indentation-induced damage area than the carbon–glass ([(±45)_c/(0,90)_g]_4s) hybrid woven laminates. These findings on different stacking sequences provide insights into surface layer behavior and interfacial failure in glass–carbon hybrid composites for designing surface-engineered laminates with improved resistance, energy absorption, and residual compressive strength. The results support the advancement of hybrid woven composite laminates and the development of durable, high-performance materials for structural applications. Full article

The composite primary structures of railway vehicles endure not only mechanical loads including tension, compression, bending, and torsion, but also external impacts, such as by the crushed stone in ballast. In the present study, the low-velocity impact response of preloaded hybrid composite laminates with different thicknesses is examined using a finite element method based on a progressive damage model. The hybrid plate consists of carbon fiber-reinforced unidirectional and woven prepregs. The progressive damage model, based on the 3D Hashin model, is validated by experiments on hybrid laminate, and further compared with the post-impact appearance obtained from CT scans. Preloading, considered to be tensile, compressive, or shear, corresponds to different positions in a bending beam with flanges and a web. Finally, the effects of impact energy, preloading, thickness, and impact angle on the dynamic response are analyzed, with an emphasis on new results and failure mechanism analysis comparing the influence of preloads under a given impact energy and different thicknesses. Full article

In this research paper, the ±45 biaxially oriented woven flax and its hybrid flax/carbon composite laminates are manufactured by the vacuum bag technique using vinyl ester as the resin binder and the samples are characterized to evaluate their tensile, flexural and impact properties. Combining natural fibers with conventional materials typically creates a hybrid composite that shows optimal mechanical properties with partial sustainability. The flax/carbon variant exhibited superior tensile strength values of 383.88 MPa and 32.60 GPa, which are about 3.5 and 2.7 times higher than the flax composites, their flexural strengths are around 415.57 MPa and 25.02 GPa, respectively, and they have an impact resistance of 12.67 J. Full article

This paper aims to study the low-velocity impact (LVI) response and compression after impact (CAI) performance of carbon/aramid hybrid woven composite laminates employed in marine structures subjected to different energy impacts. The study includes a detailed analysis of the typical LVI responses of hybrid woven composite laminates subjected to the impact with three different energies, as well as a comparative analysis of cracks and internal delamination damage within impact craters. Additionally, the influence of different impact energies on the residual compressive strength of hybrid woven composite laminate is investigated through CAI tests and a comparative analysis of internal delamination damage is also conducted. The results indicate that as the impact energy increases, the impact load and CAI strength show a decreasing trend, while impact displacement and impact dent show an increasing trend. The low-velocity impact tests revealed a range of failure modes observed in the hybrid woven composite laminates. Depending on the specific combination of fiber materials and their orientations, the laminates exhibited different failure mechanisms. Buckling failures were observed in the uppermost composite layers of laminates with intermediate modulus systems. In contrast, laminates with higher modulus systems showed early damage in the form of delamination within the top surface layers. Full article

Hybrid composite materials have been widely used to advance the mechanical responses of fiber-reinforced composites by utilizing different types of fibers and fillers in a single polymeric matrix. This study incorporated three types of fibers: basalt woven fiber and steel (AISI304) wire meshes with densities of 100 and 200. These fibers were mixed with epoxy resin to generate plain composite laminates. Three fundamental mechanical tests (tensile, compression, and shear) were conducted according to the corresponding ASTM standards to characterize the steel wire mesh/basalt/epoxy FRP composites used as plain composite laminates. To investigate the flexural behavior of the hybrid laminates, various layer configurations and thickness ratios were examined using a design of experiments (DoE) matrix. Hybrid samples were chosen for flexural testing, and the same procedure was employed to develop a finite element (FE) model. Material properties from the initial mechanical testing procedure were integrated into plain and hybrid composite laminate simulations. The second FE model simulated the behavior of hybrid laminates under flexural loading; this was validated through experimental data. The results underwent statistical analysis, highlighting the optimal configuration of hybrid composite laminates in terms of flexural strength and modulus; we found an increase of up to 25% in comparison with the plain composites. This research provides insights into the potential improvements offered by hybrid composite laminates, generating numerical models for predicting various laminate configurations produced using hybrid steel wire mesh/basalt/epoxy FRP composites. Full article

Woven flax-carbon hybrid polyamide biocomposites offer a blend of carbon fibers’ mechanical strength and flax’s environmental advantages, potentially developing material applications. This study investigated their thermal behavior, degradation kinetics, and durability to water uptake and relative humidity exposure and compared them with pure flax and carbon composites with the same matrix. The hybrid composite exhibited intermediate water/moisture absorption levels between pure flax and carbon composites, with 7.2% water absorption and 3.5% moisture absorption. It also displayed comparable thermal degradation resistance to the carbon composite, effectively maintaining its weight up to 300 °C. Further analysis revealed that the hybrid composite exhibited a decomposition energy of 268 kJ/mol, slightly lower than the carbon composite’s value of 288.5 kJ/mol, indicating similar thermal stability. Isothermal lifetime estimation, employing the activation energy (E_d) and degree of conversion facilitated by the Model Free Kinetics method, indicated a 41% higher service life of the hybrid laminate at room temperature compared to the carbon laminate. These insights are crucial for understanding the industrial applications of these materials without compromising durability. Full article

Hybridizing carbon-fiber-reinforced polymers with natural fibers could be a solution to prevent delamination and improve the out-of-plane properties of laminated composites. Delamination is one of the initial damage modes in composite laminates, attributed to relatively poor interlaminar mechanical properties, e.g., low interlaminar strength and fracture toughness. This study examined the interlaminar bond strength, flexural properties, and hardness of carbon/flax/polyamide hybrid bio-composites using peel adhesion, three-point bending, and macro-hardness tests, respectively. In this regard, interlayer hybrid laminates were produced with a sandwich fiber hybrid mode, using woven carbon fiber plies (C) as the outer layers and woven flax fiber plies (F) as the inner ones (CFFC) in combination with a bio-based thermoplastic polyamide 11 matrix. In addition, non-hybrid carbon and flax fiber composites with the same matrix were produced as reference laminates to investigate the hybridization effects. The results revealed the advantages of hybridization in terms of flexural properties, including a 212% higher modulus and a 265% higher strength compared to pure flax composites and a 34% higher failure strain compared to pure carbon composites. Additionally, the hybrid composites exhibited a positive hybridization effect in terms of peeling strength, demonstrating a 27% improvement compared to the pure carbon composites. These results provide valuable insights into the mechanical performance of woven carbon–flax hybrid bio-composites, suggesting potential applications in the automotive and construction industries. Full article

Hybrid composites are expanding applications in cutting-edge technology industries, which need materials capable of meeting combined properties in order to guarantee high performance and cost-effectiveness. This original article aimed for the first time to investigate the hybrid laminated composite thermal behavior, made of two types of fibers: synthetic Twaron^® fabric and natural curaua non-woven mat, reinforcing epoxy matrix. The composite processing was based on the ballistic helmets methodology from the North American Personal Armor System for Ground Troops, currently used by the Brazilian Army, aiming at reduced costs, total weight, and environmental impact associated with the material without compromising ballistic performance. Thermal properties of plain epoxy, aramid fabric, and curaua mat were evaluated, as well as the other five configurations of hybrid laminated composites. These properties were compared using thermogravimetric analysis (TGA) with its derivative (DTG), differential thermal analysis (DTA), and thermomechanical analysis (TMA). The results showed that the plain epoxy begins thermal degradation at 208 °C while the curaua mat at 231 °C and the aramid fabric at 477 °C. The hybrid laminated composites curves showed two or three inflections in terms of mass loss. The only sample that underwent thermal expansion was the five-aramid and three-curaua layers composite. In the third analyzed temperature interval, related to the glass transition temperature of the composites, there was, in general, an increasing thermal stability behavior. Full article

In recent years, many researchers have focused on the preparation of carbon and basalt fiber-reinforced composites. As a result, the composites have gained popularity as an alternative to traditional materials such as wood, steel, and aluminum. Carbon and basalt fibers were used in a bidirectional woven mat, with particulates varying from 0 to 15 wt% nanoparticle SiC. The hybrid laminates were fabricated through vacuum bag infusion methods. The novelty of the research work lies in studying the influence of nanoparticle SiC-combined carbon and basalt fibers arranged in six stacking sequences, with LY556 used as polyester matrix. Specimens were prepared and tested as per ASTM standards. Tensile, flexural, impact, and hardness tests were performed on the obtained specimens and average values were obtained. It was found that 15% SiC filler addition enhanced (20%) the mechanical properties. Scanning electron microscope photos revealed the bonding between the fiber mat and the matrix of thecrystal structure. The obtained tensile strength was 346 MPa and the flexural strength was 388 MPa. Dynamic mechanical analysis showed that mechanical properties were improved with the addition of 15% SiCnanoparticles. Hence, this method can be used to manufacture structural applications and automotive parts. Full article

The present investigation was conducted on the low-speed impact response of quasi-isotropic [±45/0/90°]_xs hybrid composite through laboratory level experimental tests. The purpose was to understand the behaviour that the different stacking sequences of hybrid glass/carbon fibre composites has on the ability of the material to sustain loads during low-speed impact events without developing critical structural failure in the material and improving the impact energy absorption properties, which is a relevant matter in aerospace and automotive industries. Drop-weight impact tests were carried out on two different laminates, with different stacking sequences, each of which were 16 symmetric inter-ply hybrid laminates named GC [+45G/−45C/0G/90C]₄s and, respectively, G-C [+45G/−45G/0G/90G/+45C/−45C/0C/90C]₂s, where G stands for glass fibre and C for carbon fibre. Both were comprised of epoxy matrix reinforced carbon/E-glass fibre woven fabric composites. The outcome of changing the hybrid stacking sequence, on the impact performances, was discussed. The damage morphologies and local failure mechanisms were analysed using visual inspection and a high-resolution laser scanner. Under 33 J impact energy, both tested hybrid composites exhibited approximately 10 kN peak load. Nevertheless, one key parameter, the time to peak load, significantly changed; the damage initiation threshold for GC samples occurred immediately before 6 kN, whereas for G-C samples this threshold appeared much earlier. This type of behaviour was partly connected to the delay in the propagation of delamination and fibre breakage, which was influenced by the high elastic energy absorption of the carbon fibres when compared with the glass fibres. The absorbed energy was higher for GC configuration, whereas a higher DI was observed for samples G-C indicating that a high percentage of the total energy was dissipated through the propagation of in-plane and out-of-plane fibre/matrix cracks. No perforation was observed on either configuration; nevertheless, the damage area significantly changed both in size and appearance from one configuration to another. Full article