Composites Part C Open Access最新文献

The bumper beam assembly absorbs the kinetic energy and encounters deformation during low and high-velocity impact crash collisions and accidents. An optimal bumper energy-absorbing system should fulfill pedestrian safety requirements and be crashworthy in both high- and low-speed collisions. Bumper beams made of traditional metallic materials, especially from high-strength steel, are heavyweight under low production capacity. The lightweight structure of the assembly can be achieved by using composite materials to replace the metals addressing the weight issues. In this review article, literature related to bumper beam materials is studied along with applications and the best possible and optimum option to be considered as a replacement for metals. Different parameters which affect the design of the bumper beam assembly are also reviewed. The design of bumper beams has been studied based on the conceptual design and their importance in the early stage of manufacturing. The paper also discussed the comparison of different manufacturing processes used to fabricate bumper beam assembly. Moreover, literature related to experimental investigations is also studied and reviewed with respect to the numerical models of bumper beams based on different parameters. Based on the comparison, it is concluded that numerical models can be effectively used in the design of a high-performance bumper beam system.

The long-term bond degradation and strength retention of flexural bond prisms strengthened with carbon fiber-reinforced polymer (CFRP) composite and galvanized steel mesh (GSM) systems, bonded to concrete using epoxy adhesives and cement-based mortar under aggressive conditioning regimes are compared in this paper. Notched prisms strengthened using low-cord density steel mesh (LSM) with epoxy (SME-strengthened) and cement mortar (SMM-strengthened), and CFRP-epoxy systems were weathered under saline water and direct sunlight for a period of 28 and 540 days. The results of the study were analyzed based on experimentally obtained ultimate load (P_u) values and empirically calculated average bond shear stress (τ_avg) and prism strength retention (R_p) values. The bond strength degraded by 39 and 34 % in CFRP strengthened, 2.9 and 33 % in SME strengthened, and 2.8 and 10.8 % in SMM-strengthened specimens following the 540-day exposure to saline water and direct sunlight, respectively. The average prism retention ratio was calculated to be 0.61 and 0.66 for CFRP-strengthened, 0.97 and 0.67 for SME-strengthened, and 0.97 and 0.89 for SMM-strengthened specimens after 540 days of saline water and direct sunlight exposure. Flexural prism environment strength reduction factors (C_E) were proposed as 0.60, 0.95, and 0.95 for CFRP, SME, and SMM-strengthened specimens under saline water exposures and 0.65, 0.65, and 0.85 for CFRP, SME, and SMM strengthened specimens under direct sunlight exposures. Saline water exposure was observed to be most critical to all strengthening systems. Although CFRP-strengthened specimens showed minimum degradation in load-carrying capacity under both conditioning regimes, they showed maximum bond strength reduction in contrast to SMM-strengthened specimens. It was observed that the choice of bonding agent significantly influenced the extent of bond strength degradation under extreme exposure regimes, like those that prevail in the UAE and the Persian Gulf.

Composite materials fabricated via additive manufacturing are becoming more relevant in ready-for use products used in engineering applications like aerospace structures, propellers, electric vehicles, or sandwich cores. Continuous Fiber Reinforced Polymeric (CFRP) composites are 3D-printed composites with tailor-made properties due to the capability of the printing process to deposit matrix and fiber whenever required. However, CFRP products behave differently and have lower mechanical properties than traditional composites. This study aimed to analyze the impact strength of CFRP specimens with gyroid infill and the effects of two build (flat and on-edge) and two raster (0° and 45°) orientations on impact behavior. The gyroid infill helps to obtain a light-weight structure and it has been used in energy absorption applications showing excellent mechanical behavior in thermoplastic 3D-products. The specimens were manufactured using Onyx as the matrix and aramid fiber as the reinforcement materials. The impact energy absorption of CFRP composites was measured using unnotched Izod impact specimens. The impact tests results were statistically analyzed, revealing that the build orientation directly and significantly affects the impact behavior, resulting in higher impact absorption when flat orientation is used to produce CFRP composites. The impact strength of CFRP composites increased 8 times, and 2 times for flat and on-edge oriented specimens, respectively compared to pure Onyx specimens. The variation in impact energy absorption between raster orientations in both build orientations was not significant, the difference in flat-oriented specimens at 0° and 45° was only 0.2 J, and between on-edge-oriented specimens at 0° and 45° was only 0.089 J. Also, the after impact specimens were analyzed to categorize the different failure modes observed. The after-impact analysis showed poor impregnation between aramid and onyx layers, causing delamination, fiber bridging, and fiber exposure failures. The combination of Aramid, Onyx, and a non-solid infill (gyroid) demonstrated positive results in impact behavior, obtaining high-impact absorption (165 kJ/m²) with no more than 56 % of fiver volume. The impact properties information of CFRP composites made with aramid fibers is still very scarce, joined to the lack of information on the impact properties of CFRP composites with non-solid infill, like gyroids or sinusoidal path infills. The results of this research open the possibility of using non-solid infill in CFR process that can be used to manufacture and test ready-for-use CFRP products in tasks that require high-strength, low-weight structures and impact energy absorption.

This work explores the feasibility of adopting an LSI produced C/SiC composite to build an aeronautical Auxiliary Power Unit system muffler. The study first covers the experimental material characterization through tensile and compressive tests. The material properties are characterized also after exposing the samples to an oxidizing atmosphere, that is typical for the proposed application. The material response is characterized by significant non-linearities and a pseudo plastic response, which were numerically modeled using a Drucker-Prager model. The detailed design of the muffler is described and verified, for different loading conditions, using a Finite Element model. Finally, a full-scale prototype is produced and assembled, thus proving the technological feasibility of the design. The manufacturing phase required to study and understand the phenomena that were leading to defects in the proposed closed axial symmetric shape, and to implement suitable technological solutions in order to get an acceptable prototype.

This work explores a type of composite called thermoplastic polymer-fiber-reinforced polymers (PFRPs), often referred to as self-reinforced composites (SRCs). A representative PFRP was exemplified using unidirectional (UD) ultra-high-molecular-weight polyethylene (UHMWPE) fibers embedded in a high-density polyethylene (HDPE) matrix. The effects of compression molding temperature and pressure on the mechanical and morphological behaviors of the filament-wound PFRPs with various fiber volume fractions ($V_f$) were experimentally investigated.

The results elucidate the evolution of morphologies and tensile properties of the PFRPs due to thermal melting, fiber misalignment from pressure, and $V_f$-induced structural variance, which has not been comprehensively reported yet. The highest specific tensile strength and modulus of the PFRP laminae reach 600 MPa/(g/cm³) and 31 GPa/(g/cm³), respectively. These properties are comparable to glass-/aramid-fiber-reinforced polymers (GFRPs, GFRTPs, AFRPs, and AFRTPs), with PFRPs exhibiting better ductility (specific strain at peak load $\approx$ 4%/(g/cm³)) than other common polymer composites.

The motivation for this work was the high recyclability of PFRPs, which can be recycled by melting both the fibers and the matrix, and then reshaped them for re-manufacturing composites to maximize the efficiency in material reuse. This process simplifies the implementation of closed-loop recycling, re-manufacturing, and reuse to support sustainability in composites. This work aims to contribute to advancing thermoplastic PFRPs for their potential applications in various industries.

Biomass and agricultural wastes have increased exponentially and are significant concerns resulting in further environmental and societal issues through the accumulation and burning of waste. Waste burning emits fumes, which release and increase greenhouse gas emissions into the atmosphere. During the production and harvesting of nuts, nutshell waste can account for 20 to as much as 80 wt.% of the total production volume, leaving a considerable amount to accumulate and be underutilized. China and the USA are the most significant producers of nutshells globally, of which, peanuts, walnuts, and almonds are the highest produced. In addition to biomass waste, plastic pollution causes the contamination of land and marine environments and the leaching of toxic substances during their decomposition under the action of environmental conditions. Interest in biodegradable polymers, their investigation, and production have quickly risen recently. This addresses the challenges of the linear economy cycle and offers a solution to waste management by improving degradation rates and applications. As such, biodegradable and biobased polymers can decrease energy consumption by 65 % and greenhouse gas emissions by 35 to 80 %. Therefore, this timely review focuses on using nutshell wastes such as walnuts, almonds, peanuts, pecan, pistachios, and hazelnut shells as fillers in biodegradable polymers and fabricating sustainable composites via various processing techniques. Current uses and environmental considerations of nutshell waste-based composites have been discussed based on feasibility and economic impact.

Natural fibre composites (NFCs) are not durable in the long run because of the susceptibility of natural fibres to environmental conditions and specifically moisture. Hybridizing NFC laminates externally, with synthetic fibre reinforcements, may improve durability, due to their inherent environmental resistance. This work aims to investigate the effects of glass hybridization, on flax fibre composites, studied via accelerated ageing. In specific, the durability of hybrid flax/glass fibre reinforced polymer composites, with two recyclable polymer matrices was investigated. Unidirectional (UD) flax and UD glass fibre reinforcements were employed to fabricate laminates, with two fully-recyclable off-the-shelf resin systems, as matrix: (i) a bio-based epoxy resin and (ii) an acrylic liquid thermoplastic (Elium®). In addition, a standard petroleum-based epoxy polymer matrix was for reference purposes. Weathering and hygrothermal ageing were used to test the durability of coupons, exposed to UV radiation/condensation/water spray environment (weathering ageing), and full-immersion in distilled water at 23, 40, and 60°C (hygrothermal ageing). In all cases, ageing was performed for a total duration of 56 days. The performance of the unaged and aged composite coupons was assessed and compared in terms of flexural and viscoelastic performance as well as SEM (Scanning Electron Microscopy) analysis. It was revealed that the addition of glass fibres with flax fibres in the hybrid composites improves the performance and better resistance against ageing environments than their neat flax fibre composites.

The aim of this study is to explore the use of sustainable basalt fiber (BF) as compared to glass fiber and talc in injection molded engineering polyamide 6,6 (PA 6,6) plastic composite. Basalt fibers having lengths of 3 mm and 12 mm were added to PA 6,6 at 23 and 30 wt.% to fabricate the composites. The addition of basalt fiber restricts the mobility of the polymer chain in the composites, leading to its increased viscosity. Rheological results showed that the out-of-phase response to the applied stress indicated that the 3 mm basalt fiber composite could dissipate more energy, and the elastic behaviour of the composite under deformation increased with increasing basalt fiber wt.%. The fiber length had a larger effect on the mechanical properties of the composites as compared to the fiber load. The 12 mm basalt fiber composites at 23 wt.% and 30 wt.% produced higher tensile strength and modulus than the 3 mm basalt fiber composites while the 3 mm basalt fiber composite at 30 wt.% resulted in a 25 % increase in flexural strength. The experimental and the theoretical modulus predicted by the rule of mixtures showed an interaction between the matrix and the basalt fiber. Morphological analysis shows more agglomeration in composites with 3 mm fiber than the 12 mm. Glass fiber-reinforced PA 6,6 showed slightly higher performance than basalt fiber-reinforced PA 6,6. However, the basalt fiber-reinforced composites demonstrated better performance in tensile strength, flexural modulus, flexural strength, and heat deflection temperature than talc-reinforced composites.

In this study, an analytical and numerical analysis of a hybrid sandwich structure with a lattice core produced by additive manufacturing with composite facesheets is carried out. This paper aims to analytically calculate the mechanical behavior of the hybrid sandwich structure under three-point bending and to verify the results by the finite element method. The analytical method used in this article for the analysis of the composite sandwich structure is the First-Order Shear Deformation Theory (FSDT). The numerical analysis of the hybrid sandwich structure was performed in ANSYS. In the analyses, homogenized models of lattice structures, which had been previously validated, were employed to reduce the number of elements and thereby save time during the solution process. As a result of the study, an extensive investigation into the deformation, shear, and normal stress values of sandwich structures with lattice cores of varying aspect ratios has been carried out. The findings suggest a potential for optimization in lightweight structures, which could lead to innovative advancements in design and manufacturing processes within the aerospace and automotive sectors.

The research focus has shifted towards lightweight structures with high energy absorption capabilities due to advancements in automotive safety technology. This study specifically investigates the impact of cross-sectional area on the energy absorption characteristics of hemispherical composite shells. The experimental phase involves characterizing a glass fiber epoxy composite, followed by the manufacture of hemispherical composite shell specimens with varying cross-sectional areas. These specimens undergo quasi-static axial compressive loading, and the energy absorption parameters are analyzed. The results indicate a significant influence of the composite cross-sectional area on the crushing behavior of hemispherical shells, with a observed decrease in specific energy absorption as the cross-sectional area increases. Additionally, a 3D Finite Element (FE) model is created using ABAQUS FE code to numerically simulate the crushing process. The model’s predictions are compared and validated against experimentally measured values, demonstrating a satisfactory correlation.