Search Results (45)

This paper mainly investigates the ice-impact resistance of PVC foam sandwich beams for polar ship protective structures through low-velocity impact experiments and nonlinear finite element simulations. An experimentally validated elastic–plastic coupled model, accounting for ice crushing and large structural deformation, was used to examine the effects of core density and face-sheet thickness distribution on the ice-impact response of sandwich beams. Results show that the upper face sheet undergoes local indentation and global bending, the lower face sheet mainly bends globally, and the foam core exhibits local compression and overall bending, while compressive deformation accompanied by ice crushing and spalling occurs at the front part of the ice impactor. Moreover, the effective structural stiffness decreased during plastic loading as local indentation and core compression developed, whereas the unloading stiffness was higher than the effective stiffness during plastic loading. Energy dissipation primarily comes from ice crushing, face-sheet plasticity, and core compression. Increasing core density reduces deflection and core compression but increases peak force. Among the three face-sheet configurations examined at a constant total thickness, the configuration with a thinner upper face sheet and a thicker lower face sheet produced a smaller final deformation of the lower face sheet. This study provides a useful reference for ice-resistant design of sandwich structures in polar ships. Full article

This paper presents a theoretical approach based on the FSDT to study the acoustic vibration performance of rib-stiffened PVC foam sandwich structures with reinforcing and weakening phases when submerged in water. The complex core layer with reinforcing and weakening phases is homogenized to an equivalent orthotropic layer. Building upon this framework, the governing equations of motion for rib-stiffened PVC foam sandwich structures under the boundary conditions of a simply supported type are derived, incorporating the coupling interaction between the reinforcing ribs and the sandwich plates. Considering the influence of the underwater environment, with the Helmholtz equation governing the continuity of the acoustic pressure field and the Euler equation regulating the fluid–structure interaction interface continuity, the Navier method is subsequently employed to solve for the natural frequencies and acoustic vibration responses. For the purpose of verifying the proposed approach, the predicted results are contrasted with both the literature-derived data and numerical simulation results. Finally, parametric research is further conducted to explore the effect of the parameters of the rib and core layers on the underwater acoustic vibration characteristics. The conclusions drawn from this study can provide meaningful guidance for engineering design and optimization of such rib-stiffened sandwich structures, incorporating both reinforcing and weakening phases in underwater engineering applications. Full article

A sandwich structure consists of a light core and two thin laminates bonded on both sides of the core. Sandwich structures have applications in structural constructions such as wind turbine blades and marine boats. These structures may experience low-velocity impacts from maintenance operations or during service conditions; thus, it is important to study these low-velocity impacts. In the current study, a sandwich structure was fabricated from PVC foam core and unidirectional glass fibres using the vacuum resin infusion method. The PVC foam core used was of 10–20 mm thickness while the face sheet had two different thicknesses. The panel was tested for impact strength using drop weight equipment at impact energies at three energy levels. The results were reported for damage area, force–time, force–displacement and energy–time curves. Full article

A method has been developed to delaminate the organic components (paint, foam) from the steel skins of composite polyisocyanurate (PIR) steel insulation panels at ambient temperature and in 20 min using selected solvents combined with ultrasonication. Using this method, polyisocyanurate foam can be selectively delaminated from polymer-based paint (PVC plastisol) and, in turn, the polymer paint can be selectively delaminated from the galvanised steel. Both the foam and paint are removed as intact layers, leaving the galvanised steel intact for the next steps of recycling, enabling the subsequent individualised recycling of each sub-component or layer. Several solvents have been tested, and the data show that H-bonding solvents (e.g., H₂O, alcohols) are less effective at delaminating these polymers. Whilst high polarity, medium H-bonding acetonitrile and DMSO remove PVC paint and some PIR foam, the most effective solvent for both PIR foam and PVC paint removal is medium polarity, medium H-bonding acetone. Full article

Glycyrrhizic acid and its derivatives are a crucial class of glycoside terpenoids with significant pharmaceutical and food industry applications. The biotransformation of glycyrrhizin (GL) into glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG) and glycyrrhetinic acid (GA) can enhance the production of these valuable compounds. This study aimed to develop strategies to improve the catalytic and operational stability of β-glucuronidase from wild-type Talaromyces pinophilus Li-93, previously known as Penicillium purpurogenum Li-3 (w-PGUS), for efficient GL hydrolysis. Whole cells of T. pinophilus Li-93 expressing w-PGUS were capable of directly converting GL into GAMG. To enhance enzyme stability and reusability, three polymeric supports including, polyurethane foam (PUF), loofah sponge (LS), and polyvinyl chloride (PVC), were evaluated for immobilization of w-PGUS from the fermentation medium. Among these, PUF was the most effective immobilization support, yielding higher immobilization efficiency, GAMG production, and biomass retention. Under optimized conditions (1% PUF, 1.5 g.L⁻¹ w-PGUS inoculum, pH 5.0, 36 °C, 180 rpm), the immobilized w-PGUS produced a final GAMG yield of 3.90 g.L⁻¹, achieving 67.10% immobilization efficiency within 72 h. The PUF-immobilized w-PGUS retained 37.51% of its initial activity after 10 repeated batch reactions, whereas free w-PGUS retained only 6.21%. Additionally, the storage stability of immobilized w-PGUS was significantly higher (40.22%) than that of free w-PGUS (14.74%) after 30 days. Immobilization slightly reduced the initial yield due to mass-transfer limits but enabled much higher cumulative GAMG production through improved stability and reusability. Full article

In the design of marine structures, structural design remains a critical activity, heavily guided by classification society rules that define dimensions of the structural elements. With the development of increasingly complex structures and the increasing use of composite materials in ship structural design, accurate knowledge of material properties, particularly those of sandwich panel cores, is essential for direct calculations. This article presents experimental data and numerical analysis results for the PVC core of sandwich panels, the selection of appropriate material models from the LS-DYNA standard material database, and the development of a user-defined material model to accurately capture the physical behaviour of foam cores in sandwich constructions. The comprehensive dataset obtained from polymer foam tests is made publicly available to support future structural calculations. Full article

Human activities have triggered microplastic pollution, and estuaries have emerged as critical yet understudied ecosystems in Chile. This study investigated sediment microplastic pollution in the Lenga (highly industrialized) and Tubul-Raqui (fisheries village) ecosystems, characterized by contrasting anthropogenic impacts, in the Biobío Region, Chile. Microplastic particles, including fibers, foam, fragments, and film, were detected in both estuaries. The Lenga estuary, heavily industrialized, exhibited a significantly higher total abundance of microplastics compared to the Tubul-Raqui estuary. However, the mean concentrations of microplastics in the studied estuaries are notably lower than those reported in other global studies, aligning more closely with levels found in less polluted estuaries around the world. FTIR analyses identified six types of polymers in Lenga, with polyamide (PA) being the most prevalent, constituting 35% of all polymers detected. Conversely, in Tubul-Raqui, polyvinyl chloride (PVC) emerged as the predominant polymer, comprising 25% of the total. Furthermore, significant correlations were observed with sediment physico-chemical parameters, such as organic matter and pH. These findings confirm the existence of microplastic pollution in both estuaries, highlighting the necessity of continued monitoring and assessment of potential environmental impacts in these ecologically valuable ecosystems. Full article

This study presents a foam sandwich structure reinforced with carbon fiber columns (FSS-CFC), which exhibits strong mechanical and sound insulation properties. The FSS-CFC consists of two face-sheets and a polyvinyl chloride (PVC) core containing multiple CFC cylinders arranged in a periodic array. The sound transmission loss (STL) measured in acoustic tube experiments closely aligns with the finite element simulation results, validating the reliability of the present research. Through characteristic analyses, the study reveals the sound insulation mechanism of FSS-CFC, identifying three distinct sound insulation dips caused by the standing wave resonance of the core, column-driven same-direction bending vibrations, and column-constrained opposite-direction bending vibrations in the sheets. It is also demonstrated that the sound insulation performance of FSS-CFC is insensitive to hydrostatic pressure changes. Finally, the FSS-CFC is optimized by the genetic algorithm in MATLAB and COMSOL. The optimized FSS-CFC displays good improvements in both mechanical and acoustic performance compared to the initial structure. The average STL in the frequency of 500 Hz to 25,000 Hz has increased by 3 dB, representing an improvement of approximately 25%. The sound insulation mechanism in FSS-CFC could provide valuable insights for the development of a pressure-resistant acoustic structure for use on deep-water vehicles. Full article

This study optimizes the structural design of a composite wing shell by minimizing mass and maximizing the first natural frequency. The analysis focuses on the effects of polyvinyl chloride (PVC) foam thickness and the fiber orientation angle of the inner carbon layers, with the outer layers fixed at ±45° for torsional rigidity. A Multi-Objective Genetic Algorithm (MOGA), well suited for complex engineering problems, was employed alongside Design of Experiments to develop a precise response surface model, achieving predictive errors of 0% for mass and 2.99% for frequency. The optimal configuration—90° and 0° fiber orientations for the upper and lower layers and a foam thickness of 1.05 mm—yielded a mass of 412 g and a frequency of 122.95 Hz. These findings demonstrate the efficacy of MOGA in achieving innovative lightweight aerospace designs, striking a balance between material efficiency and structural performance. Full article

In this research, a new method of treating wastewater is introduced using a highly recyclable and sustainable material derived from coconut oil. This material aims to address the issues commonly faced by conventional sorbents, such as limited performance and costly production. These challenges impede a sorbent material from unlocking its full utility in treating wastewater. An exceptional sorbent material was synthesized by incorporating coconut shell-based activated carbon (AC) into a coconut oil-based polyurethane matrix to produce an activated carbon-infused polyurethane (ACIP). The effective adsorption was elucidated by the synergistic interaction between the ACIP material and methylene blue (MB) through electrostatic attraction, π-π interactions, and hydrogen bonding. To provide an exhaustive analysis of the ACIP material, several analytical techniques were employed, including Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) analysis, X-ray diffraction (XRD) analysis, and thermogravimetric analysis (TGA). A detailed assessment using a fixed-bed column setup investigated its adsorption behavior by encompassing various factors such as inlet concentration, adsorbent bed height, feed flow rate, and solution pH. Results revealed that the ACIP composite exhibited a maximum adsorption capacity of 28.25 mg g⁻¹. Empirical evidence with a high correlation coefficient (R² > 0.93) obtained from the Thomas and Yoon–Nelson model suggests the suitability of the composite material to operate efficiently under these diverse circumstances. Notably, after five consecutive adsorption–desorption cycles, ACIP demonstrated its remarkable reusability by maintaining 86% of its regeneration efficiency. Given its outstanding performance and potential for scalability, this innovative ACIP composite presents a more sustainable approach to addressing wastewater issues within industrial environments. Full article

This paper examines the mechanical performance of fibre-reinforced composite sandwich structures (FRPSSs) for maritime applications, focusing on the impact bending and damage sequence after seawater exposure. Glass-fibre/epoxy facesheets with various PVC foam core configurations underwent low-velocity single and multiple impacts. An in situ moisture-uptake methodology monitored moisture ingress until saturation. Results showed moisture uptake reduced impact bending capacity and bending stiffness to varying degrees. While energy-absorption performance remained largely unchanged under single impacts, significant differences were noted for multiple impacts. Failure analysis confirmed the reductions in some damage modes such as facesheet fracture, indentation, and core shear failures, while core shearing, delamination, core/facesheet debonding, and fibre breakage were identified as the main failure modes. These insights enhance understanding and optimisation of FRPSSs for improved out-of-plane damage resistance in marine applications. Full article

Background: The primary flame retardants in vehicles, organophosphates (OPEs) and polybrominated diphenyl ethers (PBDEs), volatilize and accumulate in the enclosed vehicle environment, posing potential health risks. Amidst the rising number of vehicles, the scrutiny of persistent organic pollutants like OPEs and PBDEs in vehicles is increasing. This study investigates occupational and nonoccupational population exposure to specific OPEs (TnBP, TBOEP, TEHP, TCEP, TCiPP, TDCiPP, TPhP, EHDPP) and PBDEs (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, BDE-209) in vehicle dust. Methods: Data on OPEs and PBDEs in vehicle dust were sourced from PubMed and Web of Science. We applied PCA and PMF to identify pollutant sources and assessed health risks using the hazard index (HI) and carcinogenic risk (CR) methods. Monte Carlo simulations were conducted for uncertainty analysis, evaluating variable contributions to the results. Results: The predominant OPE in dust samples was TDCiPP (mean value: 4.34 × 10⁴ ng g⁻¹), and the main PBDE was BDE-209 (mean value: 1.52 × 10⁴ ng g⁻¹). Potential sources of OPEs in vehicle dust include polyvinyl chloride (PVC) upholstery, polyurethane foam (PUF) seats, electronics, carpet wear, hydraulic oil, and plastic wear in the brake system. PBDE sources likely include automotive parts, PVC upholstery, seats, carpets, and electronics. The 90th percentile HI and CR values for occupational and nonoccupational populations exposed to OPEs and PBDEs indicate that the noncarcinogenic and carcinogenic risks are relatively low. A sensitivity analysis showed that the pollutant concentration, time in the vehicle, exposure frequency, and duration significantly influence health risks. Conclusions: The health risks to both occupational and nonoccupational populations from exposure to OPEs and PBDEs in vehicle dust are relatively low. Full article

Polyvinyl chloride (PVC) and polyethylene terephthalate (PET) contribute significantly to global plastic waste, with only 9% recycled in recent years. In this work, these plastic wastes were upcycled as functional fillers to improve the rigid polyurethane foam (RPUF) properties. To attain this target, we leveraged the intrinsic polarity of the C=O and C-Cl groups of PVC and PET to induce intermolecular attractions with the N-H groups of the polyurethane matrix, evidenced by the observed IR peak shifts. This enhanced the nucleating effect during foaming, increasing the foams’ compressive strengths by 77% and 22% with the addition of 10% PVC and 5% PET filler, respectively. Furthermore, the addition of PVC and PET fillers increased the foam volume. Thus, the collective utilization of PPW and its corresponding impact on the CO-based RPUF’s properties signifies a reduction in carbon dioxide emissions by 14.15% and 17.52% for PVC and PET, respectively. Moreover, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed improved thermal stability and degradation profiles of the produced RPUFs. Overall, this work highlights potential advancement in environmentally responsible upcycling strategies for common end-of-life plastic wastes, while enhancing rigid foam properties. Full article

Considering the different structural strength requirements of different parts of fiberglass yachts, carbon fiber/glass fiber hybrid reinforcement can be applied to the skins of sandwich panels in special areas. This paper designs and prepares 12 foam sandwich panel samples composed of pure carbon fiber, a carbon fiber/glass fiber hybrid, pure glass fiber skin, and PVC and SAN foam sandwich, with reference to the layup structure of the outer panel of a fiberglass yacht. Through a comparative analysis of low-speed impact experiments, edge compression experiments, and short beam three-point bending experiments, we seek the optimal carbon fiber/glass fiber hybrid layup design scheme for local structures to guide production. The results show that a reasonable hybrid carbon fiber layup in fiberglass skin can effectively reduce the low-speed impact damage of the sandwich structure, reduce edge compression damage, and improve the bending and compression resistance of sandwich structure. The impact resistance, compression resistance, and shear resistance of the SAN sandwich structure are stronger than the PVC sandwich structure. The carbon fiber/glass fiber hybrid SAN foam sandwich structure can be used for the local structural reinforcement of special parts such as the bow, side, and main deck of fiberglass yachts. Full article

This paper explores a novel structure aimed at enhancing its blast resistance performance by adding a layer of polyurea coating to the steel-PVC foam-steel sandwich panel. The response of 13 different arrangements of sandwich panels under explosive loading was studied using numerical simulation. The response process can be divided into three deformation stages: (1) Fluid-structure interaction; (2) Compression of the sandwich panel; (3) Dynamic structural response. The dynamic responses of the various sandwich panels to close-range air blast loading were analyzed based on the deformation characteristics, deflection, effective plastic strain, energy absorption, and pressure of the shock wave. The study draws the following conclusions: Reasonably adding a layer of polyurea to the traditional PVC foam sandwich panel can enhance its resistance to shock wave absorption, with a maximum increase of 29.8%; the optimal arrangement for explosion resistance is steel plate-PVC foam-polyurea-steel plate when the polyurea is coated on the back; and the best quality ratio between polyurea and PVC foam is 1:7 when the polyurea is coated on the front. Full article