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Highlights Compared with the common numerical analysis of out‐of‐plane low‐velocity impact (LVI) of composite laminates, this paper established a finite element model (FEM) for out‐of‐plane LVI of unreinforced laminates and Z‐pin‐reinforced laminates. The mechanical response and damage morphology of the model after impact at energies of 5, 10, 30, and 50 J were verified with experiments. Through mechanical response research, it was found that the numerical analysis models of LVI of unreinforced and Z‐pin‐reinforced laminates have higher prediction accuracy for maximum impact force, maximum displacement, and energy absorption of the laminate. The simulation results showed that the Z‐pin reinforced laminates had higher impact force and lower maximum displacement compared to the unreinforced laminates. From the LVI simulation, it was observed that the damage morphology of the laminate's surface and interior indicated minor fiber damage, which correlated well with the fiber damage observed in the experiments. In contrast, matrix damage played a dominant role during the impact, leading to extensive damage. This extensive damage occurred due to the loss of the stress transfer medium caused by matrix damage, which subsequently resulted in fiber damage. Comparison of simulated and experimental mechanical response Criteria for determining the initiation of matrix/fiber damage Simulation analysis of Z‐pin reinforced laminates Intra‐laminar fiber/matrix damage and inter‐laminar delamination [ABSTRACT FROM AUTHOR]

This paper presents the effect of varying the type of Z‐pin on the delamination bridging performance of unidirectional composite laminates. Carbon and Kevlar Z‐pins were inserted in thick composite laminates using the pre‐hole insertion Z‐pinning process and their bridging performance characterized across the different mode‐mixity range. The bridging response indicated that Kevlar Z‐pin experienced load reduction driven by interfacial friction (Stage III), which was absent in the Carbon Z‐pin. When Mode II dominated the bridging crack, Kevlar Z‐pin showed partial pullout and fiber shear cracking, while the Carbon Z‐pin exhibited clean transverse fracture. Although the bridging load obtained by the Carbon Z‐pin was twice that of Kevlar Z‐pin, the Kevlar Z‐pin provided a higher interlaminar fracture energy. The superior bridging performance of Kevlar Z‐pin is correlated with the enhanced ductility. Moreover, the resin‐rich area was involved in deformation and provided the extra axial load of Z‐pin. Highlights: The comparison of mixed‐mode bridging mechanism between Kevlar Z‐pin and Carbon Z‐pin.Reveal the variation of multi‐directional load and energy consumption with mixed‐mode angle in thick laminates.Detailed scanning electron microscope observation to understand failure characteristics of ductile Z‐pin.Evidence that the extra axial load of Z‐pin provided by resin‐rich area. [ABSTRACT FROM AUTHOR]

Cracks induced by internal stresses compromise the structural integrity of ceramic laminates. Such stresses can be classified into thermal stress derived from thermal expansion mismatch and shrinkage stress derived from shrinkage mismatch. Analytical models have been proposed for the former, whereas only numerical predictions have been explored for the latter. In this study, an equation is constructed to predict the shrinkage stress by modifying an elastic solution proposed in previous studies. We fabricated laminates with three‐layer sandwiched structures using only alumina specimens with high and low densities to control the shrinkage and avoid thermal mismatch. Surface cracks were initiated when the shrinkage stress exceeded the flexural strength of the surface layer. Although the original strength of the surface layer was 308.8 MPa, the laminates' flexural strength was lower than that because of shrinkage constraint. Our results demonstrate that the shrinkage stress was successfully estimated analytically using a few material properties measured in an ordinary environment. This study will ensure the structural integrity of ceramic laminates in laminate designs. [ABSTRACT FROM AUTHOR]

The outermost layer of a fire proximity suit needs to conform to a strict requirement of radiant protection performance (RPP) ≥ 20s, which is indicative of its ability of offering a protection for at least 20s duration from second degree burn upon radiant heat exposure (84 kW/m2). Typically, this layer is fabricated by laminating a single‐side metallized PET (SMPET) layer with glass fabric. However, upon erosion of the deposited metal, this laminate is rendered unsuitable due to loss of reflectivity. Here, we explore the possibility of replacing the SMPET with its dual‐metallized analogue (DMPET) and determine the effect of increasing the optical density (OD) on the adherence and protection level. Metallized films with OD varying from 2.2 to 4.8 were laminated with glass fabrics of twill, satin and plain weave pattern using a silicone adhesive. The peel adhesion strength of laminates prepared using DMPET was found to be higher (1.01 ± 0.03 N/mm), as compared to SMPET (0.63 ± 0.03 N/mm) and the resulting films did not undergo delamination during flexing. Laminates prepared from satin woven glass fabric exhibited lowest flexural rigidity followed by twill and plain woven glass fabric. Protection offered by the laminate from convective heat was quantified in terms of the thermal protective performance (TPP), and the abraded laminate prepared using DMPET (OD‐4.8) was found to meet all the mandatory requirements of proximity clothing, offering an RPP of 27 s and a TPP of 62 cal/cm2 s. In comparison, SMPET laminates exhibited lower level of adhesion and offered an RPP of only 7.5 s. [ABSTRACT FROM AUTHOR]

Information on the sintering activation energy is currently focused on evaluation of single-phase ceramic systems. This work shows the results of high-temperature dilatometry measurements of layered and particle composites based on alumina and zirconia. Layered composites with different layer thickness ratios and particle composites with variable composition in the entire concentration range were prepared by electrophoretic deposition allowing manufacturing composites with precious design and strongly bonded interfaces. The phenomena observed during the high-temperature dilatometry measurements are discussed, and the data were used to calculate the sintering activation energies of composites using the modified Master Sintering Curve concept. By covering a wide range of composite designs, it was possible to determine differences in activation energies and to show their dependence on the direction in the case of laminate composites given by the directionally dependent sintering behaviour. Sintering activation energies of layered composites were always higher than for monoliths due to constrained sintering showing maximum sintering activation energies at lower volumes of zirconia in the layers for longitudinal and transversal orientation of the samples. A similar trend was identified in particle composites due to slowed down alumina densification by the pinning effect. Additionally, mechanical properties represented by Vickers hardness and indentation elastic modulus were related to the microstructure developed during sintering. The effects of interconnectivity of phases present in the composites together with other parameters of the microstructure were described. [ABSTRACT FROM AUTHOR]

A two-stage quantitative damage detection method based on difference method and improved particle swarm optimization algorithm was proposed to solve the structural damage problem of laminates during processing and service. Firstly, the structural damage element was defined by the method of reducing the elastic modulus of the element, and the modal parameters of the numerical model of the laminate under different damage conditions were obtained by analyzing the structural vibration characteristics. Secondly, an improved particle swarm optimization algorithm was used to quantitatively calculate the exact location and degree of damage. The proposed algorithm constructed the objective function through the flexibility matrix of the modal parameters of the tested structural model and the iteratively updated finite element model. The variation factor was introduced to make the algorithm effectively escape the local convergence. The MS operator greatly reduced the influence of the healthy element on the damage degree of the real damaged element. The results show that the improved particle swarm optimization algorithm can accurately identify the location and damage degree of the damaged elements in the composite laminates. [ABSTRACT FROM AUTHOR]

Highlights The development of high‐performance ultra‐high molecular weight polyethylene (UHMWPE) fiber laminate is of great significance in the field of bulletproof materials. However, due to the poor heat resistance of UHMWPE fibers, it is challenging to achieve exceptional mechanical properties in laminates prepared via hot‐pressing. In this study, we employ a self‐made ultraviolet (UV) cross‐linked fully drawn yarn of UHMWPE (UVFDY), which exhibits excellent heat resistance, to prepare a UVFDY/unsaturated polyester resin (UPR) laminate through hot‐pressing. The laminate possesses outstanding mechanical properties, which includes high Barcol hardness (~40 HBa), high tensile strength (~800 MPa), and high storage modulus (~13.7 GPa at 25°C), surpassing those of most conventional UHMWPE fiber laminates. Its remarkable mechanical properties are primarily attributed to the highly cross‐linked networks of cured UPR and the stable structures (gel content ~89%, crystallinity ~81.5%, orientation ~93%, and smoother fiber surface) of UVFDY during hot‐pressing. This work not only provides valuable insights into the preparation of high‐performance UHMWPE fiber laminates but also promotes applications for the self‐made UV cross‐linked UHMWPE fiber. Novel laminate possesses high Barcol hardness. The tensile strength and storage modulus of novel laminate are excellent. UV irradiated fiber with high structural stability during hot‐pressing. [ABSTRACT FROM AUTHOR]

Nowadays, ultra high molecular weight polyethylene (UHMWPE), allows the combination of lightweight, high strength and is praised for the design of severely loaded structures. It has become a good option for lightweight armour solutions. It is therefore important to characterise its mechanical behaviour. Up to now, strain rate effects on mechanical behaviour have been poorly explored. In this work, this issue is tackled by studying the strain rate influence on the in-plane deformation, in shear and tension of the Tensylon® HSBD30A, a UHMWPE dedicated to ballistic and blast protection. Two laminates of Tensylon® of respective orientation [0 °/90°]20 and [±45°]20 were subjected to static and split Hopkinson tensile bar (SHTB) tests. A new mounting system was designed, and new specimen shapes were used to match the experimental setup configurations. Digital image correlation (DIC) was used to measure the in-plane strain. A significant strain-rate dependence on the material behaviour.is evidenced. Besides, results exhibit a higher strength for the [0°/90°]20 specimen than for the [±45°]20 one. Despite some limitations, the proposed setup and measurement methods allowed visualisation of strain rate effects on the stress-strain relationship for strain rates ranging from the quasi-static regime to the dynamic one (1500 s–1).

The inherent anisotropy and variable stiffness characteristics exhibited by Variable Angle Tow (VAT) composite materials offer significant possibilities for enhancing the performance of corresponding structures. Through appropriate selection of the curved fiber paths, it becomes feasible to design structures that are both lightweight and efficient. However, conducting mechanical analysis on VAT composite structures is of considerable challenges, particularly in seeking analytical solutions. In view of this, this paper aims to investigate the thermomechanical buckling behavior of VAT composite laminates with elastically restrained edges and presents an analytical solution for the studied problem. The analysis is based on the assumption that the fiber orientation angle of each lamina varies linearly or nonlinearly along the x direction, and the fundamental equations for thermomechanical buckling of VAT laminates are derived using the classical laminated plate theory. The analytical solution is obtained through the combined utilization of Taylor series and Frobenius series. Furthermore, a comprehensive parameter analysis is conducted to assess the impact of different factors, such as fiber paths and elastic support stiffness, on the critical thermomechanical buckling load and mode of VAT laminates. The resulting findings serve as a valuable reference for VAT laminate design, while the proposed analytical solution can be employed as a benchmark for validating other numerical results. [ABSTRACT FROM AUTHOR]

AbstractThe structure for optimization is a composite cylinder subjected to hydrostatic pressure. The customization is in the method of incorporating the balanced laminate constraint using a while loop which not only improves buckling resistance but also drastically reduces the computation time. The formulation of the objective function is carried out in a novel way. The third customization is in considering geometric variables along with layup in optimization to arrive at the most optimal configuration. The results suggest a significant increase in buckling load ranging from 61.3% to 92.2% and a reduction by about 76.3% in time required for optimization. [ABSTRACT FROM AUTHOR]

Let p> 2 be a given exponent. In this paper, we prove, with the best constant, the weak-type (p,p) inequality ∥ T m f ∥ L p , ∞ (R d) ⩽ C p ∥ f ∥ L p (R d) for a large class of non-symmetric Fourier multipliers Tm obtained via modulation of jumps of certain Lévy processes. In particular, the estimate holds for appropriate linear combinations of second-order Riesz transforms and skew versions of the Beurling-Ahlfors operator on the complex plane. The proof rests on a novel probabilistic bound for Hilbert-space-valued martingales satisfying a certain non-symmetric subordination principle. Further applications to harmonic functions and Riesz systems on Euclidean domains are indicated. [ABSTRACT FROM AUTHOR]

Various techniques have been proposed to manufacture prosthetic sockets, which are essential in improving the quality of life among amputees and individuals with special needs. However, the fabrication of prosthetics using the available approaches is uneconomical due to the type of materials utilized during the production, as well as the direct methods that use expensive materials to produce prosthetic parts. Considering this, it is crucial to enhance the direct methods by exploiting cost-effective materials to produce prosthetic parts with desirable behaviors. Therefore, this study aimed to compare the fatigue performance of below-knee (BK) prosthetic sockets manufactured using three different techniques: laminate, direct, and novel. The three sockets specimens were first manufactured. Specimen A was made via the direct method using 4 layers of carbon fiber as the reinforcement and AX140401 as the matrix. Specimen B was also fabricated via the lamination method using 4 layers of carbon fiber as the reinforcement and lamination resin + hardener acrylic as the matrix. Finally, specimen C was made via the direct novel method using 4 layers of carbon as the reinforcement, and the matrix was composed of 20% polyurethane resin (part A: resin, part B: hardener) + 80% acrylic. Subsequently, the pressure distribution at the contact point between the socket and the residual limb was analyzed using the FSOCKET device. Furthermore, the numerical analysis included the distribution of the stress and the highest internal pressure, the number of cycles ascertained through the utilization of the SOLIDWORKS software. Based on the results, the S-N curves for each specimen show that all three specimens behaved similarly. Using the F-socket, the pressure during the patient's walking cycle reached its highest point at 190 kPa. In addition, applying ground reaction force from the bottom of the direct, lamination, and novel BK prosthetic sockets demonstrated the pressure distribution of the part that reacts to the loading condition. The SOLIDWORKS program revealed from the pressure distribution of the three sockets measured a maximum internal pressure of 191 kPa, 193 kPa, and 191 kPa sequentially, which was close to the pressure within the F-socket. Besides, the number of cycles for the direct, lamination, and novel BK prosthetic sockets was 1,332,345, 1,202,345, and 1,203,567 cycles. In summary, all three specimens fabricated via the direct, lamination, and novel methods achieved similar fatigue performance of BK prosthetic sockets. So, the novel BK prosthetic socket wad designed in which fabricated using a new matrix material was considered acceptable, similar to specimens A and B. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The 3D printing parameters are known to have a significant impact on manufactured parts, and the layered morphology of these parts makes mechanical design analysis for engineering applications difficult. In this work, the tensile strengths and microhardness of 3D printed polylactic acid (PLA) specimens with different orientations and numbers of individual layers of mesh material (polyvinyl chloride – PVC) were investigated as a laminate composite. Composite specimens were obtained using 3D printing via fused deposition modelling (FDM). Moreover, the influence of printing parameters (i.e. infill density and layer height) and the number and orientation of reinforced meshes on the mechanical response was investigated. Fracture strength of PLA/PVC laminate composites ranges from 31.30 MPa (3 PVC mesh layers; mesh height position: 25 %│50 %│75 %; infill density: 60 %; PVC mesh orientation: 90°│45°│90°; layer height: 0.2 mm) to 18.62 MPa (without PVC mesh; infill density: 30 %; layer height: 0.1 mm) demonstrating a significant impact of the number of the PVC mesh layers, infill density of PLA and layer height on the final mechanical parameters of printing PLA/PVC elements. The surface hardness at the micro load level showed that the number of reinforcement layers affects the microhardness value, as well as material filling and mesh orientation. The specimen with the following parameters gave the best results: layer height: 0.2 mm; 3 PVC mesh layers; infill density: 60 %; PVC mesh orientation: 90°│45°│90°. The average hardness values for one layer and three layers of mesh were in accordance with tensile test results.

This study investigates the feasibility of using a composite material comprising slate reinforced with cork sheets for architectural purposes like facades and wall coverings. The research involves the comprehensive characterisation of both slate and cork materials along with the evaluation of the silicone adhesive used in their bonding process, specifically Sikasil® HT from SIKA®. It was found that both slate and cork exhibited low wettability, which was enhanced through cold plasma treatment. Subsequently, a composite sandwich structure was fabricated and subjected to impact testing in a drop tower, along with fire resistance evaluations. The fire tests revealed that when subjected to a flame of 900 °C for 15 min, the slate alone heated rapidly, reaching 500 °C within 3 min on the side opposite to the flame. However, the sandwich structure reached 260 °C on the cork side (opposite to the flame) at 7.5 min, maintaining this temperature until the deterioration or detachment of the cork between 11 and 12 min. This provided insulation and delayed ignition. The sandwich structure maintained its fire resistance due to the insulating properties of cork and the superior thermal resistance of silicone compared to other adhesives up to 260 °C. Overall, the results suggest the potential suitability of this sandwich structure for architectural applications. Its favourable adhesion properties and acceptable fire resistance indicate that it could serve as a viable alternative for construction materials in architectural contexts. [ABSTRACT FROM AUTHOR]

This paper develops a thermoelectric (TE)–piezoelectric (PE) hybrid structure with the PE layer acting as both a support membrane and a sensor for the TE film for microelectronics applications. The TE and PE layers are assumed to be perfectly bonded mechanically and thermally but electrically shielded and insulated with each other. The thermo-electro-mechanical responses of the hybrid bilayer under the TE generator operation conditions are obtained, and the influence of the PE layer on the TE energy conversion efficiency is investigated. The numerical results for a Bi2Te3/PZT-5H bilayer structure show that large compressive stresses develop in both the PE and TE layers. With a decrease in the PE layer thickness, the magnitude of the maximum compressive stress in the PE layer increases whereas the maximum magnitude of the stress in the TE layer decreases. The numerical result of the TE energy conversion efficiency shows that increasing the PE layer thickness leads to lower energy conversion efficiencies. A nearly 40% reduction in the peak efficiency is observed with a PE layer of the same thickness as that of the TE layer. These results suggest that design of TE films with supporting/sensing membranes must consider both aspects of energy conversion efficiency and the thermomechanical reliability of both the TE and PE layers. [ABSTRACT FROM AUTHOR]

Copyright of Materiały Budowlane is the property of Wydawnictwo SIGMA-NOT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Global economic development and efforts to enhance overall quality of life yielded growth in the construction and building sector, increasing not only the demand for materials but also waste generation. Its efficient management should take full advantage of the exceptional properties of building materials. The presented work is the first reported study on possibly using waste rigid polyurethane (PUR) foam, commonly applied as thermal insulation, as particle-shaped low-density filler for manufacturing hybrid epoxy-basalt composites. It investigated the potential management of waste PUR foam by applying it as a functional filler to hybridize epoxy-basalt composites. Herein, 1, 2, 5, and 10 wt% PUR powder were introduced into the thermoset-based composites prepared using the vacuum bag method. A comprehensive analysis of mechanical and thermomechanical properties correlated with changes in the composite structure revealed the beneficial aspects of the waste filler addition associated with increased heat deflection temperature and mechanical damping ability. Introducing micrometric domains of the waste filler changed the composites' fracture character. It enabled maintaining the impact strength of composites containing up to 5 wt% of PUR powder at the level of unfilled epoxy resin. However, despite that, the incorporation of PUR powder unfavorably affected tensile and flexural performance, yielding a significant drop in moduli and strength. [ABSTRACT FROM AUTHOR]

Copyright of Materiały Budowlane is the property of Wydawnictwo SIGMA-NOT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is commonly acknowledged that polymer composites in service are often subjected to not only intricate mechanical loads but also harsh environmental conditions. The mechanical and thermal properties of five particular composites are explored here. The composites are composed of laminates of glass cloth type "E" sheet infilled with a duroplastic matrix. This is a thermoset polymer—epoxy resin with different molecular weights. The composites were fabricated by IZOERG company, which is based in Poland. The final articles were 1.5 mm thick by 60 cm long and 30 cm wide, with the glass layers arranged parallel to the thickness. Young's modulus and tensile strength were measured at room temperature. Using the thermal analysis of dynamic mechanical properties (DMTA), the values of the storage modulus and the loss modulus were determined, and the damping factor was used to determine the glass transition temperature (Tg). It was revealed that the nature of changes in the storage modulus, loss modulus, and damping factor of composite materials depends on the type of epoxy resin used. Thermal expansion is a crucial parameter when choosing a material for application in cryogenic conditions. Thanks to the TMA method, thermal expansion coefficients for composite materials were determined. The results show that the highest value of the coefficient of thermal expansion leads the laminate EP_4_2 based on brominated epoxy resin cured with novolac P. Duroplastic composites were characterized at cryogenic temperatures, and the results are interesting for developing cryogenic applications, including electric motors, generators, magnets, and other devices. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lightweight and thin, soft armour panels (SAPs) with minimum back-face signature (BFS) are desirable for developing bullet-resistant jackets. This research explores the ballistic resistance of different structural forms, namely two-dimensional (2D) woven fabrics, unidirectional (UD) woven fabric laminates, and cross-ply laminates of disentangled ultra-high molecular weight polyethylene (DPE) tape used in as-received or twisted tape forms. Three SAPs were prepared from laminates made from two woven fabrics of twisted tape and cross-ply laminate of untwisted tape. All SAP areal density fixed in the range of 4.5 ± 0.3 kg.m−2. In ballistic test (9 × 19 mm bullet), SAPs made from twisted tape got perforated due to high stress concentration and slower wave propagation. SAP made from DPE tape with the lowest areal density was not perforated by the bullet (430 m·s−1) and exhibited perforation ratio and BFS as 0.18 and 22.2 mm, respectively, which are at par with those of SAPs developed from commercially available popular high-performance fibers. Post-impact failure analysis of SAPs at macro- and microscopic scales also supported the superiority of cross-ply laminate of DPE tape over UD woven fabric laminates of twisted tape. [ABSTRACT FROM AUTHOR]

Optimization of the structure of piezoelectric transducers such as the proper design of matching layers can increase maximum wave energy transmission to the host structure and transducer sensitivity. A novel configuration of an ultrasonic transducer, where elastic metamaterial insertion is introduced to provide bulk wave mode conversion and to increase wave energy transfer into a substrate, is proposed. Configurations of layered elastic metamaterials with crack-like voids are examined theoretically since they can provide wide band gaps and strong wave localization and trapping. The analysis shows that the proposed metamaterial-based matching layers can sufficiently change wave energy transmission from a piezoelectric active element for various frequency ranges (relatively low frequencies as well as higher ones). The proposed configuration can also be useful for advanced sensing with higher sensitivity in certain frequency ranges or for demultiplexing different kinds of elastic waves. [ABSTRACT FROM AUTHOR]

In this work, a Mg-Zn-Y (ZW31) alloy with good plasticity was introduced into 10 μm 10 vol% SiCp/AZ91 composite materials (PMMCs) via the extrusion compound method, and then the ZW31/PMMC laminate was prepared via multi-pass hot rolling. The hot deformation mechanism and elevated temperature tensile fracture mechanism of ZW31/PMMC laminates were studied using the elevated temperature tensile test. The elevated temperature deformation mechanism is influenced by the strain rate. At low strain rates, grain boundary slip is the primary elevated temperature deformation mechanism of the ZW31/PMMC laminate. However, at high strain rates, the activation of pipeline diffusion is facilitated by the particle deformation zone (PDZ) in the PMMC layer with a high dislocation density, leading to the dominance of dislocation climbing as the main mechanism for elevated temperature deformation of the laminate. Additionally, the implementation of a ZW31/PMMC laminate structure effectively inhibits the initiation and propagation of cavities and microcracks within the laminate layer along the normal direction (ND) while simultaneously blunting crack tips via lattice dislocation emission toward the ZW31 layer. Upon cracking of the PMMC layer, stress concentration occurs in the fracture area of the ZW31 layer, ultimately resulting in necking-induced detachment. [ABSTRACT FROM AUTHOR]

A methodology of optimising composite frame structures has been applied to three selected geometries. A cyclic process driven by predefined objectives achieved the most desirable parameters through adjustments in winding angles and tube ply thicknesses. A geometry resembling a crane structure underwent initial analyses, allowing for the determination of appropriate settings for the surrogate model's training phase, considering accuracy and computational time. Its final design was influenced by prevalent bending and tension loads, resulting in near-zero winding angles and a range of thicknesses that met displacement, strength, and weight requirements. A second geometry with further restrictions was also considered. Finally, for a third geometry, winding angles were tailored to accommodate torsion forces. The presented optimisation process resulted in volume reduction while maintaining displacement and strength parameters. These findings highlight the effectiveness and transferability of the optimisation approach across different geometries. [ABSTRACT FROM AUTHOR]

This study aims to ascertain the material characteristics that are intrinsic to the prepreg layer within a laminated composite structure. The elastic modulus of the lamina, a primary determinant of composite structural behavior, is the focal point of this analysis. This parameter has been assessed by employing reverse-engineering techniques on a composite composed of sequentially stacked prepregs. The investigation entailed simulating the behavior of the composite under static loads and conducting modal analyses to reflect both static and dynamic conditions. The findings indicate that the elastic modulus values derived from combined tensile and modal analysis simulations exhibit superior accuracy compared to those obtained through tensile simulation alone. Specifically, the maximum prediction error for E1 (the tensile-direction elastic modulus of one lamina sheet) decreased from 1.17% to 0.28%, and that of E2 (the transverse-direction elastic modulus of one lamina sheet) decreased from 12.01% to 7.30%. Further simulations incorporating fabrication error variances underscored the critical nature of precise E2 analysis. The proposed methodology evidenced a more accurate assessment of E2, underscoring its potential to enhance the reverse-engineering process in composite material design. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) is a composite material made of a polymer matrix reinforced with fibers. Hybrid composites are referred to as high-performance FRP materials used in safety-critical structural applications. Generally, FRP composite laminates are very weak in their out-of-plane properties, to address this issue unidirectional (UD) Glass laminates are prepared by modifying the matrix using plasma-treated multi-walled carbon nanotubes (MWCNTs) in epoxy matrix and compared fracture toughness characteristics with low-cost micro fillers like Aluminum oxide (Al2O3) and Sodium Carbonate (Na2CO3). These Nano and Micro fillers are loaded with 0.5wt%, 1wt% and 2wt% in the epoxy matrix while making FRP laminates. Adding these fillers into the epoxy matrix was caused a significant increase in the out-of-plane load-bearing capacity of the composites as compared to plain Glass epoxy laminates. Thus, the fracture toughness was enhanced by 20-26% and 14-17% under mode I and mode II loading respectively. Further, a Scanning electron microscopic analysis was also done on delaminated glass laminates to understand the failure mechanisms

The performance/weight ratio of fiber reinforced polymer matrix composites makes them the material of choice for structural applications in many fields such as aerospace, aeronautics, automotive and civil engineering...etc. In polymer matrix composites, the fibers used as reinforcement are mainly synthetic fibers such as carbon and/or glass fibers. To ensure the low cost of using fiber-reinforced materials in motor vehicles, it is proposed to selectively incorporate carbon fibers to enhance glass fiber composites along the roadway, and to enhance glass fiber composites along the main load path. For this purpose, we conducted a behavioral study of hybrid epoxy thermoset polymer matrix laminates to highlight the influence of alternate hybridization of glass and carbon fibers on the physical-mechanical behavior of the materials.The results obtained show that the alternated hybridation of the fibers has a significant influence on the tensile properties; and it affected the density, hardness and flexural properties significantly.

The Hashin's criteria are useful in composite structural applications because of their simple concept and their theoretical results are relatively close to that got in the experimental parts. In the present study, in the present study, the failure of the composite laminates under static loading have been developed predicted using Hashin's Criterion. Nonhomogeneous stresses within a structure may induce a complicated failure scenario whereby one ply at a point can initiate failure and can affect also other plies at the same point or the same ply in different neighboring points. With neglecting the possibility of interlaminar failure, only in-plane loads are considered in this state. The results showed that the failure analysis was proposed to simulate the nonlinear laminate behavior and progressive damage of selected laminates under to their ultimate strength. In our approach, the finite element analysis is performed using MATLAB software to study the effect of tensile and compressive loading on the failure of epoxy resin laminate AS4/3501-6. [ABSTRACT FROM AUTHOR]

Purpose: The natural frequencies of the layered composite panel with combined damage have been performed numerically considering the debonding between the consequent layers of laminae around the Cut-out. The damage influence on structural strength has been studied to investigate the realistic responses. Methods: Initially, the cut-out abided panel model is derived with the help of a computational tool (ABAQUS) with and without delamination. Moreover, the computational model is derived via a quadrilateral shell element (four-noded) with twenty-four degrees of freedom (DOF) per element. The responses are computed by taking the influences of the individual damages and the combined cases, i.e., the cut-out, debonding, and cut-out associated with the delamination. Results: The outcomes are compared with the recorded experimental frequency values for the combined influences of damages. The comparisons between the simulation and experimental data of the first mode of fundamental frequencies indicate a close relevance with a deviation of ± 10%. After establishing the comprehensive behavior of the computational model, the same has been extended to evaluate different sets of examples by changing the geometrical and/or material-dependent parameters. Conclusions: The stiffness of the structure is affected by the presence of delamination and cut-out in specific shapes. However, the structure having circular delamination and cut-out exhibits high stiffness compared to the other two cases. [ABSTRACT FROM AUTHOR]

Filament-based unidirectional laminates of para-aramid and ultra-high molecular weight polyethylene exhibit excellent impact resistance performance. This research explored the possibility of using disentangled polyethylene (DPE) tape, instead of filaments, as an alternative impact resistant material. The effects of laminate structure, binding resin content and processing temperature on the tensile and impact properties of cross-ply laminates prepared from DPE tape was investigated. Three types of cross-ply laminates prepared from tape, woven fabric of untwisted tape and woven fabric of twisted tape were explored. Tensile properties and low velocity impact resistance of laminates were evaluated. Laminate made from woven untwisted tape showed much lower impact energy absorption than cross-ply laminate, while the woven twisted tape based laminate performed the worst. Cross-ply laminates made with low resin content showed better tensile and impact resistance performances. Cross-ply laminates prepared at higher moulding temperature showed significantly enhanced impact energy absorption than its counterpart prepared at a lower temperature. Therefore, cross-ply laminate of DPE tape with low resin content is ideal for impact resistance applications. [ABSTRACT FROM AUTHOR]

In the field of engineering materials, lightweight and ultra-lightweight composites are used in real time to a greater extent, with high-performance targeting for tailor-made systems in aerospace, automotive, and biomedical applications. Sandwich composites are among the most popular lightweight materials used in structural and vehicle-building applications. In the present investigation, one such sandwich composite laminate composed of aluminum face sheets and a high-density polyethylene core was considered to analyze sandwich composites' flexural and buckling behavior experimentally and numerically. The influence of aspect ratios, such as length to thickness and width to thickness, on the flexural and buckling performance of sandwich composite laminates was explored in the study. Laminates with different widths, namely, 10, 12, and 15 mm, and a uniform thickness and length of 3 mm and 150 mm, respectively, were used for flexural analysis, whereas laminates with widths of 10, 12, and 15 mm and a uniform thickness and length of 3 mm and 350 mm, respectively, were used for buckling analysis. The geometrical influence of the laminates on mechanical performance was studied through performance measures such as critical bending load, flexural stiffness, inter-laminar shear stress, and critical buckling load. A significant influence of aspect ratio on the mechanical behavior of the laminates was observed using both experimental and numerical approaches. Flexural behavior was observed to be better at greater widths, namely, 15 mm, and with a minimum support span of 90 mm due to reduced spring back effects and increased bending resistance. A maximum width of 15 mm allowed for a higher buckling load capacity similar to that of bending resistance. A critical buckling load of 655.8 N seemed to be the maximum and was obtained for the highest aspect ratio, b/t = 5. The soft core and ductile metal face sheets offered combined resistance to both bending and buckling. A lower aspect ratio (span to thickness) rendered these sandwich laminates better in terms of both bending and buckling. [ABSTRACT FROM AUTHOR]

This study used finite element analysis (FEA) to model the effects of adhesive Z-connections on the thickness swelling of laminated wood composites exposed to water. We hypothesized that the area density, diameter, and spatial distribution of adhesive Z-connections will influence the ability of Z-connections to restrain thickness swelling of the composites. We tested this hypothesis by modelling a wood composite in ANSYS FEA software v. 17.0 to explore the effect of moisture on the thickness swelling of the wood composite. The results were compared with those obtained experimentally. We then examined the effect of the area density, size (diam.), and spatial distribution of the adhesive Z-connections on the thickness swelling of wood composites. Our results showed a positive correlation between the number of adhesive Z-connections in the composites and restriction of thickness swelling following 72 h of simulated moisture diffusion. Similarly, increasing the size of adhesive Z-connections also restricted thickness swelling. In contrast, different spatial distributions of Z-connections had little effect on restraining thickness swelling. Our modelling approach opens up opportunities for more complex designs of adhesive Z-connections, and also to examine the effect of wood properties, such as permeability, density, and hygroscopic swelling ratios on the thickness swelling of laminated wood composites. [ABSTRACT FROM AUTHOR]

The effect of high contrast on the multiscale behaviour of elastic laminates is studied. Mathematical modelling in this area is of significant interest for a variety of modern applications, including but not limited to advanced sandwich structures and photovoltaic panels. As an example, the antiplane shear of a symmetric, three-layered plate is considered. The problem parameters expressing relative thickness, stiffness and density are assumed to be independent. The high contrast may generally support extra length and time scales corresponding to degenerated boundary layers and propagating long-wave low-frequency vibration modes. The main focus is on the relation between these two phenomena. The developed multiparametric approach demonstrates that those do not always appear simultaneously. The associated explicit estimates on contrast parameters are established. In addition, the recent asymptotic extension of the classical Saint-Venant's principle is adapted for calculating the contribution of the degenerate boundary layer or long-wave low-frequency propagation mode. The peculiarity of the limiting absorption principle in application to layered media is also addressed. [ABSTRACT FROM AUTHOR]

Copyright of Cotton Textile Technology is the property of Cotton Textile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Advanced Textile Technology is the property of Zhejiang Sci-Tech University Magazines and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The finite element (FE) solutions of the smart (SMA: shape memory alloy fibre bonded) composite with and without crack are computed in this research. The structural model is derived mathematically considering the shear deformation effect, and the proposed functions maintain the necessary continuity of stresses. The numerical solutions are obtained via the computer code considering the blocking/recovery stress phenomenon (via marching technique) due to the inclusion of SMA fibre. The necessary correctness and the numerical results sensitivities are verified as priori. The solutions are showing an improvement of structural stiffness (decrease in deflections around 22–27% and 14–22% for the prestrain values 3–5% and 10–30% volume fraction of shape memory alloy fibre, SMA) due to the activation of SMA (under elevated temperature) fibres. Finally, the influences of all different structural design (aspect ratio, thickness ratio, boundary conditions, load intensities and crack dimension), material (SMA relevant data), environment and damage effects on the static flexural deflections are examined through a series of examples. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of using a composite material comprising slate reinforced with cork sheets for architectural purposes like facades and wall coverings. The research involves the comprehensive characterisation of both slate and cork materials along with the evaluation of the silicone adhesive used in their bonding process, specifically Sikasil® HT from SIKA®. It was found that both slate and cork exhibited low wettability, which was enhanced through cold plasma treatment. Subsequently, a composite sandwich structure was fabricated and subjected to impact testing in a drop tower, along with fire resistance evaluations. The fire tests revealed that when subjected to a flame of 900 °C for 15 min, the slate alone heated rapidly, reaching 500 °C within 3 min on the side opposite to the flame. However, the sandwich structure reached 260 °C on the cork side (opposite to the flame) at 7.5 min, maintaining this temperature until the deterioration or detachment of the cork between 11 and 12 min. This provided insulation and delayed ignition. The sandwich structure maintained its fire resistance due to the insulating properties of cork and the superior thermal resistance of silicone compared to other adhesives up to 260 °C. Overall, the results suggest the potential suitability of this sandwich structure for architectural applications. Its favourable adhesion properties and acceptable fire resistance indicate that it could serve as a viable alternative for construction materials in architectural contexts.

• An advanced semi-analytical hybrid approach simulates the dynamic behaviour of guided waves-based SHM systems and smart structures. • The advantages of the proposed method compared to existing numerical methods are demonstrated. • The method combines advantages of the semi-analytical and direct numerical method. • The hybrid method accurately analyses resonance regimes and performs fast detailed parametric analysis of SHM systems. An advanced semi-analytical hybrid approach for simulating the dynamic behaviour of guided waves-based SHM system is proposed here. The proposed numerical method simulates wave excitation, scattering and sensing in a multi-layered elastic waveguide with a system of internal delaminations and piezoelectric/elastic inhomogeneities mounted on the surface the waveguide. The frequency domain spectral element method is applied to describe wave motion in surface-mounted obstacles (piezoelectric transducers, stringers, joints etc.), while the advanced boundary integral equation method is employed to calculate piezo-induced or scattered wave-fields propagating in the multi-layered waveguide with multiple delaminations. The crack opening displacements at the delaminations are interpolated via weighted Chebyshev polynomials of the second kind taking into account square-root behaviour at the tips of delaminations. The collocation and Galerkin methods are applied to satisfy boundary conditions in the contact area between surface-mounted inhomogeneities and the multi-layered waveguide. The convergence, the accuracy and the computational costs of the hybrid method are analysed, and the comparison with the finite element method is provided. The presented novel hybrid method grants opportunity to analyse resonance frequencies of a laminate with multiple delaminations and surface mounted inhomogeneties, calculate energy flow transferred from an actuator into the waveguide and provide fast parametric analysis of guided wave propagation in the considered structures. [ABSTRACT FROM AUTHOR]