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Recycling every viable material to produce new value-added products not only reduces waste, but also provides an opportunity to create sustainable and innovative solutions while preserving our natural resources. With this motivation, electrically conductive one-dimensional carbon fibers and two-dimensional aluminum flakes reinforced cellulose matrix composite papers were manufactured using recycled materials with a scalable, eco-friendly, and low-cost papermaking process. The designed composite paper showed 36.1 dB electromagnetic interference shielding efficiency (EMSE) with an absorbance-dominated performance by absorbing 98.85% of electromagnetic waves. An efficient impedance matching was obtained on the composite paper surface using reinforcements with different morphologies. Cellulose paper samples were converted to electrically conductive composites (0.415 S/cm), and the electrical conductivity was altered by tailoring the reinforcement ratios. Thermo-mechanical test results revealed that the cellulose matrix's storage modulus was increased from 1.44 to 2.1 GPa with a 46.5% improvement. The composite cellulose paper represented increased hydrophilicity with higher porosity. The environmentally friendly composite paper responses to the escalating environmental worries and possesses a tremendous possibility of being utilized as an electromagnetic shielding material. [ABSTRACT FROM AUTHOR]

Paper is a composite of fibers, air and additives where the fiber/fiber joints keep the network structure together. A study was undertaken to establish the link between the properties of the contact zone between fibers and paper performance under mechanical loading. The contact zone between fibers was investigated using light microscopy. A staining technique was developed for evaluating the influence of surface charge on fiber/fiber joint strength. The joint strength was linearly correlated with paper tensile strength and with the average amplitude of the acoustic events measured by acoustic emission testing. The fiber surface conformability was improved by changing the surface charge. This resulted in increased fiber/fiber joint strength as the relative contact area became larger. Increasing the molecular adhesion in the contact zone with the aid of strength additives also improved the fiber/fiber joint strength. [ABSTRACT FROM AUTHOR]

This paper describes the possibility of the use of paper twines as core reinforcement in thermoset pultruded sandwich composites. Paper twines and glass fiber rovings were co-impregnated with polyester resin and co-pultruded to form sandwich rods. Pultruded sandwich rods were up to 26% lighter with regard to typical monolithic glass fiber reinforced polyester rods. The specific flexural strength and Young's modulus of the sandwich rods were up to 25% higher than those of monolithic glass fiber/polyester commercial rods. Thanks to its light weight and its availability as a continuous twine, paper twines may be used with great flexibility in pultrusion of sandwich structures. This may lead to up to 20–30% weight reduction and cost saving without losing flexural performance. [ABSTRACT FROM AUTHOR]

In this paper, a three-dimensional anisotropic multi-surface model for the in-plane elastoplastic deformation of paper and paperboard is developed. The model is based on the concept of structural tensors. It employs three different yield functions and parameterised consistency conditions for three different loading scenarios. The evolution of the yield surface with plastic strain is described by multiple hardening variables. Furthermore, the evolution equations are integrated using the unconditionally stable backward Euler method. Also, the internal variables are updated using a particular form of the elastic predictor/plastic corrector algorithm. The constitutive model is calibrated from a set of simple uniaxial tension tests performed in various directions of the material and is validated against loading in other directions. Additionally, the predictive capability as well as the numerical performance of the constitutive model is accessed against an existing non-quadratic plasticity model. Finally, the applicability of the constitutive model is demonstrated by performing a tensile test on a paperboard with a hole. [ABSTRACT FROM AUTHOR]

This article is a summary of computational research conducted to assess the relationship between fold-crack resistance and bending stiffness in coated papers. Though this article is based on theoretical research, an experimental pilot coating program was undertaken in conjunction with the modeling. The objective of the computational work was to suggest ways in which coated paper could be optimized to maximize fold-crack resistance as well as bending stiffness, both of which are inversely related. Models were developed to calculate the bending stiffness, to predict the onset of failure, and based on this prediction, to calculate the residual load-carrying capacity of coated paper composites. Optimization of the coated paper composite was taken as a function of the number of coating layers used, the individual layer thickness, and the mechanical properties of the coating layers during both tension and compression. Simulations were conducted for single-, double-, and triple-coated papers keeping the properties and dimensions of the base paper substrate constant throughout. But the elastic moduli of the coatings were varied independently, though failure stress values were kept constant in order to vary the strain to failure stress and stiffness simultaneously. The optimal coating lay-up as per the hypothesis was a triple coating comprising of a thin, stiff inner coating layer; a thick, low-stiffness middle coating; and a thin, low-stiffness outer coating. The hypothesis was confirmed by the pilot coating trials. [ABSTRACT FROM AUTHOR]

An acoustic emission technique is used to quantify and position microfracture events ahead of a growing opening mode crack in paper materials containing different amounts of added starch. A mechanical model based on gradient-enhanced elasticity, containing an intrinsic length parameter reflecting the fibre-based materials microstructure, is applied to analyse the results. It is found in experiments that the addition of starch increases the tensile strength of paper significantly while the level of onset of microfracture nucleation at the crack-tip is only slightly increased. It is also found that the height of the process zone (zone in which microfractures ahead of the crack predominantly take place), measured from the crack plane, decreases with increasing amount of starch. The experimental and analytical results suggest that adding cationic starch to paper reduces the material’s sensitivity to gradients in the stress and strain fields and making the fibre network material more ‘continuum-like’. The experimental observations are shown to be qualitatively in agreement with the numerical results and lend confidence to the applied model. [ABSTRACT FROM AUTHOR]

Two-body abrasion wear rate of AA6061 aluminium alloy, AA6061-2SiC nanocomposite, and AA6061-2SiC-2Gr hybrid nanocomposites were studied using a pin on disc machine at various applied normal loads 5-20 N and 50-150 µm abrasive grit size by maintaining a constant sliding distance of 120 m. Morphology of fabricated materials, worn surfaces of tested specimens, and abrasive grit papers were analysed under a scanning electron microscope. The wear rate of the AA6061-2SiC-2Gr hybrid nanocomposite was found to be less than that of AA6061 alloy and AA6061-2SiC nanocomposite. The wear rate decreased by 19% for 50 µm, 28.2% for 100 µm, and 22.5% for 150 µm at an applied normal load of 20 N and 120 m sliding distance for Al 6061-2SiC-2Gr hybrid nanocomposite compared to base alloy. [ABSTRACT FROM AUTHOR]

Complex curved composite components often rely on multiple reference curve algorithms for path planning in automated fiber placement. However, the reference curves are typically manually drawn. Moreover, designing the reference curves follows an iterative planning-analysis-improvement process, which can be inefficient. A new approach for the automatic pre-analysis and optimized generation of reference curves for fiber placement is proposed in this paper to enhance the efficiency of reference curve analysis and generation. Firstly, a pre-analysis algorithm for reference curves based on triangular meshes is proposed. This algorithm analyzes the theoretical geodesic curvature and angular deviation of the path before its planning. Subsequently, a comprehensive evaluation index for reference curve generation is formulated based on the pre-analysis algorithm, and the reference curve is optimized using genetic algorithms. The results demonstrate that the pre-analysis algorithm accurately computes the steering radius distribution of the path. Areas with over-limit steering radius can be eliminated while maintaining angular deviations within 10° by utilizing optimized reference curves for path planning. [ABSTRACT FROM AUTHOR]

The problem of failure in the facings of a corrugated board is investigated by means of a mechanical model utilizing the principles of continuum damage mechanics. To evaluate the predictive capability of the model, experiments have been conducted on in-plane isotropic single and two-ply paper sheets manufactured in the laboratory. It is found that there is a qualitative agreement between model and experiments. The model can predict if delamination will occur before the top-ply loses its in-plane load carrying capacity due to material degradation. To circumvent delamination problems, a material with low stiffness should be used in the top-ply (as compared to the bottom-ply) and a very thin top-ply should be avoided. It is exemplified that it is possible to steer the failure mode by optimizing the degree of beating or the ply thickness. It is demonstrated that plasticity may be omitted in the analysis if one is only interested in characterizing the expected type of failure mode. An important key result is that, if the circumstances are that severe damage growth takes place in the crack-tip region, then delamination most likely occur which may be in contradiction to what is anticipated from classical theories of fracture mechanics. [ABSTRACT FROM AUTHOR]

The authors discuss the paper "Analysis of progressive matrix cracking in composite laminates II. First ply failure," by G. J. Dvorak and N. Laws regarding transverse cracking of composite. Topics discussed by authors include determination of the elastic energy that was stored in ply, determination of elastic properties of cracked plies, and the use of Young and shear modulus.

Compression-compression fatigue behavior of hybrid unidirectional/woven carbon-fiber reinforced composite laminates after low-velocity impact (LVI) was studied in this paper. The paper contains two parts. Firstly, different levels of impact energy were introduced on the specimens. Impact damage modes were obtained and characterized as fiber breakages, matrix cracks, indentation and delamination. The relationships between indentation depth/damage area and impact energy were established. Secondly, compression-compression fatigue tests were conducted on the impact damaged specimens. Fatigue life degradation trends were analyzed and fatigue limit for different types of specimens was determined. Delamination areas by depth mode and amplitude mode of C-scan showed an increasing trend with the fatigue life increasing. Stiffness decreased sharply in the early and ending stages of fatigue life. However, stiffness exhibited stable or slightly decreasing rates in the mid-stage of fatigue life. A line-shaped failure cracks going through the impact point were observed in the fatigue failure specimens. [ABSTRACT FROM AUTHOR]

Lithium Iron Phosphate (LiFePO4) microstructures have been synthesized using the sol-gel process. One-dimensional (1D) LiFePO4 microstructures were fabricated using tissue paper as a template under different temperatures to form pure phase microstructures. XRD analysis confirmed the single phase nature of orthorhombic olivine-structured LiFePO4 with Pnma space group. SEM analysis authenticated the formation of 1D LiFePO4 microstructures along with some clusters of particles. LiFePO4-multi-walled carbon nanotubes (MWCNT) freestanding sheets were prepared using a tape-casting process. Further, the electrochemical properties of LiFePO4-MWCNT freestanding sheet were analyzed through electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge analysis. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer matrix composites are increasingly considered for lightweight cryogenic pressure vessels due to their excellent combination of tailorability, specific mechanical properties, and relatively low coefficients of thermal expansion. However, significant challenges must be overcome to fully utilize PMCs for cryogenic fuel tanks in terms of transverse microcracking and subsequent permeation of cryogenic fuel. Gas permeation and microcrack densities of cryogenically cycled composites are highly influenced by their layup, ply thickness, load case, and manufacturing defects like voids and resin rich zones. There has been a significant amount of research on measuring gas permeation of composites fatigued under pure thermal or uniaxial thermo-mechanical stresses. However, results demonstrate that the gas permeability should be measured under biaxial thermo-mechanical stresses to properly gauge the leakage characteristics of damaged composites. This paper summarizes the results from over a hundred papers on the key parameters that influence the gas permeability of composites, appropriate testing methods to cycle composites for permeability measurement, methods to limit the evolution of transverse microcracks, and materials traditionally used for the fabrication of all-composite cryogenic fuel tanks. Thin plies and nanofiller-toughening of the matrix have been shown to provide significant improvements in transverse microcrack suppression within cryogenically cycled composites. [ABSTRACT FROM AUTHOR]

A new failure criterion has been developed to improve modeling of orthotropic structural composites subjected to quasi-static and impact loadings. Rather than using an analytical expression that traditionally has been employed to predict failure, a point cloud failure surface is constructed in the stress/strain space using a combination of virtual and laboratory testing. These discrete points are obtained by building a micromechanical model that is subjected to uniaxial and multiaxial states of stress until the first failure of a finite element in the model is detected. The post-peak response behavior is then activated till the element meets the erosion criterion and is deleted from the model. One of the challenges in using the generated point cloud data is the ability to correctly predict when failure onset in a finite element takes place without being too conservative. Three predictive methods are compared in this paper – Approximate Nearest Neighbor (ANN), Simplified Approximate Nearest Neighbor (SANN), and Neural Network (NN). Point cloud data from a unidirectional composite, the T800-F3900, commonly used for aerospace applications, is used for comparative evaluation of these methods. The performances are first evaluated using a standalone program not connected with FE analysis. Finally, two of these methods (SANN and NN) are implemented in a commercial finite element program, LS-DYNA, and their performances are evaluated by simulating a laboratory impact test. Results indicate that the SANN and NN implementations are robust, efficient, and accurate. [ABSTRACT FROM AUTHOR]

This study focuses on the use of bio-based materials for structural purposes in the packaging field, which requires the identification of their mechanical properties at a representative scale. The mechanical properties of bio-based materials are more variable than those of traditional composite materials. In a standard characterization approach using elemental coupons under uniaxial loading, the variability depends on the chosen representative elementary volume (REV), free edges, boundary conditions, etc. for elastic properties that are not identified for representative working conditions; this could lead to the ineligibility of these bio-based materials as structural materials. This paper contributes to the debate on how to study the response of bio-based materials within a structure, here a packaging structure as a logistic unit (LU) subjected to a compressive load simulating storage and stacking conditions. In the set of tools and methods for the design of packaging materials made of bio-based materials, an elastic nonlinear geometric finite element model (FEM) and an experimental approach are presented. The FEM allows the numerical identification of zones of interest within the LU. Inevitably, the FEM classically requires input data which are elastic properties of the equivalent homogeneous material. The design of the FEM is based on a calculation-test approach using an existing reference LU and it can be summarized in two main steps. The first step concerns the development of a FEM able to restore the experimental conditions of vertical compression imposed by transport standards for packaging. The second step is based on updating the input properties of the FEM by reverse identification, to achieve the representative working condition properties, using experimental results obtained on the existing reference LU. For the reverse identification a multi-scale investigation is mandatory. For this purpose, the linear elastic part of the load/vertical displacement curves (at the LU stiffness scale) and the displacement and strain fields measured (at the local LU scale) by 3D digital image correlation (3D DIC) are evaluated. Then, FEM property updating is carried out by reducing the deviation of displacement/strain fields between FEM and experimentally measured results (3D DIC). Finally, we explain how FEM and 3D DIC help in decision-making by allowing the recognition of zones of interest in a phase of design of new LUs with the concept of Multi-Instrumented Technological Evaluator (MITE). [ABSTRACT FROM AUTHOR]

As a notable commercial aquaculture species, channel catfish (Ictalurus punctatus) in US faces challenges including the global market competition and enhanced feed costs. Since fish bone waste is a major source of calcium and hydroxyapatite, re-utilization gives birth to several advanced products in the development of animal feed, fertilizers, and nutrition supplements. Recent research findings introduce fish bone powder (FBP) reinforcement in Fused Deposition Modeling (FDM) of plastic composites. However, FBP so far has not been widely utilized for Direct Ink Writing (DIW) 3D printing of silicone composite. In this paper, catfish bone waste has been recycled and processed with a thermal procedure. FBP reinforced silicone composite structures have been developed and manufactured using low-viscosity DIW 3D printing. Morphological and chemical structures of FBPs were analyzed and compared before and after calcination. The rheological and mechanical characterization have indicated the potential of calcinated FBP in advancing the silicone composites. With 0%–50% weight percentages of FBP, composite samples can be designed to get any specified mechanical response (0.5–1.4 MPa in 50% tension strain and 150–550 N in 30% compression strain). The shape holding, overhang, and dimensional accuracy of FBP reinforced silicone composites in single (DIW) and dual (FDM + DIW) 3D printing processes have been demonstrated and summarized. With appropriate adjustments, this FBP-based 3D printing technology can be applied to byproduct recycling of all the US food-fish species, poultry, and livestock. [ABSTRACT FROM AUTHOR]

Weft tows in 3D woven composites are commonly approximated as perfectly straight, but their undulations are inevitable in reality, although the extent of undulations in the weft tows is not as pronounced as in the warp tows. Such minor undulations in weft tows have been simulated in this paper. A previously established parametrised modelling and analysis tool for 3D woven composites has been extended to reproduce the varying geometry of the weft tows. Two novel models have been proposed to introduce the undulations, allowing their effects to be simulated. The analysis reveals that, compared to the model with straight weft tows, the effective elastic properties can be affected by the weft tow undulations. In addition, the procedure for defining varying intra-tow fibre orientation was formulated and implemented, addressing lack of consistent and robust functionalities of this kind in modern finite element solvers. [ABSTRACT FROM AUTHOR]

The paper pursues the development of a novel methodology for the rapid identification of the diffuso-mechanical properties of polymer materials based on the employment of plates subject to asymmetric moisture concentration fields. The study is carried out on epoxy plate samples equipped with a thin aluminium foil on a surface exposed to the environment to promote asymmetric moisture absorption. The asymmetric moisture fields promote deformations of the plate. Mass gain and plate curvatures are measured as a function of time during conditioning. By using a weakly coupled diffuso-mechanical model: 1D Fick's diffusion model and 2D plane stress hygroelastic model the diffuso-mechanical properties of the material can be then identified. Due to the chosen size of the experimental samples the present study allows the identification of the coefficient of moisture expansion of the epoxy material. For the material under study, the following values can be identified for saturation mass gain, water diffusivity and coefficient of moisture expansion respectively: 1.67%, 0.025 mm2.h−1, 0.1628. [ABSTRACT FROM AUTHOR]

This paper presents two methods for deformation energy or dynamic for measuring and calculating the torsion modulus, G, for composites with hollow glass microsphere (HGM) additives in unsaturated polyester resin. First, we constructed a measurement system with a torsion pendulum, a force sensor (FS), and a rotational movement sensor (RMS). Then, we deduced a relationship between force (F) and torsion angle (θ) to obtain G by deformation energy. Second, using the relaxation curve, θ in function time (t), we deduce an equation that could return the value of G for dynamic. Both techniques are non-destructive and independent of knowing the value of Poisson's ratio. We used samples of approximately 5.00 mm diameters, and the influence percentage of HGM additives differed from that of 100%Wt resin. They obtained G values by opting for these composite materials' different methods, showing a maximum deviation of 5.44%. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid utilisation of the continuum damage mechanics approach and some novel techniques was employed for progressive failure analysis of internally pressurised filament-wound composite tubes. The constructed numerical model in Abaqus software, which is employed for prediction of functional and burst failure of the tubes, was validated with an experimental failure evaluation available in the literature. Results show the high accuracy and precision of the proposed model. Therefore, this model can be used as a cost-effective virtual failure exam prior to experimental tests or as their alternative. Then, this validated model has been used in the second part of this paper for optimisation. Due to some drawbacks of the previous optimisation methods, by using the Taguchi approach capabilities, a novel strategy is proposed for optimisation of the stacking sequence of tubes under various stress ratios with taking into account the manufacturing winding angle restrictions. Results reveal that the obtained optimal stacking sequences are asymmetric and highly dependent on calculation strategies and applied stress ratio. [ABSTRACT FROM AUTHOR]

Composite laminates have become increasingly popular in industries like aerospace and shipbuilding. In practical applications, the creation of notches in composite laminates is often necessary to enable assembly and modifications. This rise in the use of notched composite laminates highlights the need for reliable methods to predict potential failures in these components. With these predictions, the safety and reliability of composite structures can be ensured by preventing catastrophic failures. The present paper investigates the use of the Virtual Isotropic Material Concept (VIMC) combined with the Finite Fracture Mechanics (FFM) criterion to predict the Last Ply Failure (LPF) load in keyhole notched composite laminates and under mode I loading conditions. Experimental tests were conducted to measure the LPF load of E-glass/Epoxy keyhole notched specimens, and the results were compared with the predicted results using the VIMC-FFM criterion. The paper also derives an expression for the Stress Intensity Factor (SIF) function for a crack that emanates from the keyhole notch tip under mode I loading conditions. The derived equation matches very well with numerical data and have a mean absolute error about 2% in the studied domain. The study shows that the VIMC-FFM criterion predicts the LPF load of keyhole notched composite laminates with acceptable accuracy and in a simple and low-cost manner. [ABSTRACT FROM AUTHOR]

Even though several works are available on the analysis of low-velocity impact (LVI) on fibre metal laminates (FMLs), there is still scope for a better understanding of the complexities associated with their analysis, making it an important area of research. Therefore, it is essential to compile and present the state-of-the-art research in this area to make the critical information available in one paper, facilitating future research. This paper thus covers the detailed review of the articles published on the LVI response of fibre metal laminates (FMLs) based on experimental, numerical and analytical approaches and the associated damage mechanisms under different impact conditions. The discussions can be mainly categorized into two broad groups, namely geometrical and material-based parameters, which significantly influence the structural response of FMLs upon impact. Additionally, the paper compares various numerical techniques reported to model the impact behaviour of FMLs, along with an overview of analytical models. Based on the manufacturing techniques and material constituents of FMLs, the paper discusses feasible methods of improving the performance of impact-prone structures. The exhaustive review of the literature finally concludes that there are scopes of investigating some of the important and relevant areas related to LVI of FMLs like the influence of relative mass of impactor and target and accurate determination of contact stiffness for accurate estimation of interface delamination. Investigating the LVI performance of advanced sandwich structures with FML facesheets is a potential area of research in this direction. [ABSTRACT FROM AUTHOR]

In this paper, numerical study on crack location and crack number on the responses of representative unit cell of unidirectional composites under tension is conducted by extended finite element method (XFEM). The composites studied here are single-crack composites, two-crack composites, and three-crack composites. Each of the composites is under tension in the fiber (x) direction. From the simulation results, the averaged strength decreases as the embedded crack number increases when composites are under tension. One interesting finding is that a crack could be a dominant crack but becomes inactive when other different cracks are in presence under the same loads. The responses of representative unit cell of composites depend upon crack location and the applied loading direction. The results from these simulations can also explain why there is discrepancy of strength prediction from the composites manufactured under the same conditions. The simulation method presented here in this paper can be used to model degree of defects (by modelling the number of cracks) and stochastic characteristics of ultimate strength (by modelling distribution of crack strength). [ABSTRACT FROM AUTHOR]

Composite sandwich structures are widely used in many areas. Light materials, such as honeycomb panels, are usually used as the cores, while stiff materials, such as fiber reinforced polymer laminates, are used as the facesheets. In this work, corrugated cores for sandwich structures were fabricated using carbon fiber reinforced polymers (CFRPs) featuring different stacking orientations. Paper, aluminum, and polypropylene honeycomb cores were also used. Additionally, CFRP was utilized as the facesheets for these sandwich structures. Bending tests, face-wise compression tests (FCT), edgewise compression tests (ECT), and accelerated aging were conducted. Finite element simulations were also performed and compared with experimental results. The results indicated that the corrugated CFRP cores with [0°]5 stacking orientation resulted in the largest flexural stiffness and ECT strength along the flute direction. Conversely, the corrugated cores with [90°]5 stacking orientation resulted in the largest transverse shear rigidity and modulus, FCT modulus and strength, and ECT strength perpendicular to the flute direction. Notably, the sandwich structures using aluminum honeycomb cores were degraded by aging the least. Since sandwich structures can be subjected to the bending load and loads in other directions, this work contributes to selecting core materials and structures of sandwich structures. [ABSTRACT FROM AUTHOR]

In this paper, the metamaterial force-chain concept is proposed, for the first time to our knowledge, to describe the stress distribution and crushing property of honeycomb materials under quasi-static compression. A novel force-chain-enhanced re-entrant honeycomb (FCERH) behavior is put forward through experiments and simulations, which forms a rhombic force chain when compressed, which is different from traditional re-entrant honeycomb (REH). It compares in detail the effects of changing the force chain on the properties of honeycomb materials, including plateau stress, Poisson's ratio, and the absorptions of energy. The results show that the FCERH has a better energy absorption capacity, and the energy absorption is increased by 91% when the strain is 0.65. Additionally, the influence of structural parameters on the enhanced force chain behavior is also discussed. The impact and blast responses of the materials are compared to verify their excellent dynamic performance. This design method has opened a new idea for the fabrication of high-performance honeycomb metamaterials. [ABSTRACT FROM AUTHOR]

The problem of obtaining anisotropic auxetic composite laminates, i.e. having a negative Poisson's ratio for at least some directions, is examined in this paper. In particular, the possibility of obtaining auxeticity stacking uni-directional identical plies is considered. It is shown that if the ply is composed by isotropic matrix and fibers, then it is impossible to obtain totally auxetic orthotropic laminates, i.e. auxeticity for each direction, unless at least one among matrix and fibers is auxetic itself. Moreover, it is shown what are the conditions, in terms of the mechanical properties of the constituents and of the volume fraction of the fibers, to fabricate uni-directional plies with which to realize laminates having a negative Poisson's ratio for some directions. Several existing materials are also examined. All the analysis is done using the polar formalism, very effective for the study of plane anisotropic problems. [ABSTRACT FROM AUTHOR]

For the first time in this paper, a composite sandwich panel with a novel circular-shaped core reinforced with silica nanoparticles (SNPs) is designed and fabricated using the vacuum-assisted resin transfer molding (VARTM) method. Carbon fibers and epoxy resin are utilized to construct the composite sandwich panels, followed by polyurethane foam injection. After fabrication, the sandwich panels undergo uniform compression testing to examine their mechanical behavior and properties. In this study, the effects of various parameters, such as core length, core height, weight percentage (wt.%) of SNPs, and polyurethane foam, on the compressive strength of the structure are evaluated. To validate the results, a finite element simulation of the sandwich panel compression test is performed using ABAQUS software, and the results obtained are compared with experimental data, showing good agreement. The results of this research demonstrate that adding SNPs within a specific range results in a considerable enhancement of the structural strength. Adding SNPs up to 3% leads to approximately a 19% increase in the compressive strength of the structure. However, adding 4 wt.% SNPs results in a decrease of about 12% in the strength of the sandwich panel. Additionally, the core's geometry significantly influences the control of compressive strength and rigidity of the sandwich panel. In other words, by increasing the core length, the compressive strength increases by 38%, while increasing the core height decreases compressive strength by about 30%. Also, it is found that adding polyurethane foam to the sandwich panel, despite a slight increase in weight, leads to a significant increase in compressive strength by about 32% and postpones its ultimate failure. Eventually, the hybrid specimen exhibits a strength approximately 57% greater than that of the pure foamless sandwich panel. [ABSTRACT FROM AUTHOR]

This study aims to assess the hybridization effect on the perforation threshold of Low-Velocity Impact (LVI) in thermoplastic glass composite laminates, incorporating layers of resin-impregnated stainless-steel mesh. Reinforcing methodologies such as hybridization are recently being adopted as a practical approach to increasing the energy-absorbing capacity of polymer composites. In the current paper, a multi-step hot press lamination method has been employed to fabricate the hybrid composite laminates strengthened with stainless-steel mesh layers. Several stacking sequences, metal mesh wire sizes, orientation and position relative to the impactor have been examined under various LVI energies. It was revealed that the LVI penetration energy was increased for the thermoplastic-based composite laminates reinforced with stainless-steel mesh layers. Furthermore, the LVI penetration energy threshold was significantly influenced by the metal mesh wire size, orientation and stacking sequence. Finally, the backlight method capability was assessed to detect the after-impact interlaminar damages. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into prepreg tape composition and its impact on the consolidation quality of in‐situ Automated Fiber Placement-manufactured laminates. Three different prepreg tape materials were investigated in terms of fiber distribution, porosity and surface roughness. Laminates were manufactured using the in-situ Automated Fiber Placement process and subsequently tested using microanalysis and mechanical testing methods. Higher quality prepreg tape material yielded lower porosity laminates and increased mechanical strength results. The best in-situ Automated Fiber Placement-manufactured laminates achieved 82 % and 88 % of hot-pressed reference tensile- and compressive strength, respectively. Prepreg tape with disadvantageous composition for in‐situ consolidation yielded up to 74 % knockdown compared to the best in-situ consolidated laminates. A five-point bending test was successfully used to determine interlaminar shear strength with significant results relating to consolidation quality. A correlation was successfully established between prepreg composition, resulting laminate consolidation quality and mechanical properties. [ABSTRACT FROM AUTHOR]

A large number of experiments show that composite materials usually show different modulus properties in tension and compression (bi-modulus). However, for actual composite engineering structures, especially complex models, the numerical simulation calculation is usually based on a single modulus. In order to consider the different modulus characteristics of composite materials in tension and compression, researchers put forward simplified constitutive models of dual-modulus materials. However, these constitutive models have not been verified by a large number of experiments, especially by complex models. In this paper, the GWFMM model is simplified and used to analyze complex structures with different modulus in tension and compression. The experimental results of stiffened plate show that the improved GWFMM model can be used to analyze different modulus of tension and compression of complex stiffened structures. In addition, the influence of elastic modulus ratio in tension and compression under different experimental load conditions is further explored, and the influence law of bending and torsion on structures with bi-modulus is discussed. The relevant conclusions provide reference for the design and optimization of full-scale composite structures in marine engineering. [ABSTRACT FROM AUTHOR]