Behavior Of Composite Structures Research Articles

Applicability of a new composite amusement ride safety device based on acoustic emission monitoring technology

Under the premise of ensuring safety, it is of great significance to realize the lightweight of the non-main load-bearing parts of amusement facilities. The purpose of this study is to study the failure process of a newly designed carbon fiber bumper by using acoustic emission technology. First of all, the design of carbon fiber anti-collision bar can effectively restrain passengers, and its weight is reduced by nearly two-thirds compared to traditional metal materials. Subsequently, the load-bearing capacity of the bumper was tested and acoustic emission monitoring was carried out. The test results show that this new type of combined structure of amusement facility has high reliability, which exceeds the safety factor of 3.5 required by the steel structure of amusement facility. In addition, Renyi entropy was used to select the best window function of short-time Fourier transform, and the frequency domain characteristics of acoustic emission signals of typical damage modes were discussed through appropriately selected windows function. A classifier based on supervised machine learning is established by combining frequency features and acoustic emission feature parameters. Furthermore, the use of classifiers helps to understand the damage behaviour of composite structures.

Vibration analysis of active composite structures embedded with long and short shape memory alloy (SMA) fibers

The shape memory effect (SME) is a source of internal compressive stresses that modify the vibration behavior of shape memory alloy (SMA) embedded composite structures. Generally, long fibers are used due to their suitability for activating SMA using resistive heating. Longer SMA fibers embedded in composite structures have their limitations in design and manufacturing. Minimal research work has been done on tuning the vibration behavior of composite structures embedded with short SMA fibers. In this research paper, an analytical model for evaluating the natural frequencies of an SMA embedded composite beam has been proposed. Effects of various design parameters for long (continuous) and short (discontinuous) SMA fibers embedded in composites have been investigated. It was observed that short SMA fibers with a higher aspect ratio can tune their frequencies similarly to long SMA fiber composites and are more effective in thicker beams. Matrix material with negative coefficient thermal expansion is more suitable for embedding SMA for modifying natural frequency in active mode.

Fracture behavior of composite piezoelectric intelligent structures formed by pasting MFC based on serial multi-scale method

The composite piezoelectric intelligent structures formed by combining piezoelectric materials with composite materials can achieve state perception and deformation control of the structure. Based on the molecular dynamics method, the continuum finite element method and the cohesive force model, the serial multi-scale research on the bonded composite piezoelectric intelligent structure was carried out from the micro, meso and macro scales. Molecular models of adhesive, macro fiber composite (MFC) surface and composite surface were established. The effects of temperature and pressure on the surface interaction energy of adhesive/MFC and adhesive/composite materials were analyzed. The traction-separation (T-S) relationship of cohesive region was obtained by virtual stretching method. Combined with the microscopic observation of the mesoscopic adhesive layer, the representative volume element (RVE) model of the mesoscopic adhesive layer considering the bubble defect was established, and the cohesive relationship curve of the adhesive layer was obtained. A double cantilever beam (DCB) macro finite element model was established to simulate the crack propagation behavior of the adhesive layer, and compared with the experimental results.

A mass spring model applied for simulation and characterization of behavior of composite structures

A mass spring model applied for simulation and characterization of behavior of composite structures

An insight into the mechanical behavior and failure mechanisms of T-stiffened composite structures with through-interface debonding defects

A robust 3D finite element model framework was established to capture the mechanical behavior and failure mechanisms of intact and through-interface debonding T-stiffened composite structures based on the progressive damage model and the cohesive zone model. Meanwhile, specimens with and without interface debonding defects were fabricated to validate the reliability and robustness of the proposed modeling framework. Finally, a parametric study was conducted on the types of interfacial debonding to further explore the effect on the buckling load, delamination initiation load, and ultimate load-carrying capacity of the composite stiffened structure. The results indicate that the load-carrying capacity of both single interface defects and double interface defects decreases gradually with increasing defect length and converges to a constant value. The reductions were 28.31% and 47.68%, respectively, compared to the intact structure. Interestingly, interfacial debonding has the most significant effect on the ultimate load at the 1/4 position. Moreover, interface debonding defects not only severely weaken the ultimate load-carrying capacity of the structure but also significantly alter the post-buckling path and failure mechanism, resulting in distinct degrees of deformation and damage morphology.

Optimizing the crashworthy behaviors of hybrid composite structures through Taguchi approach

Optimizing the crashworthy behaviors of hybrid composite structures through Taguchi approach

Thermal contraction coordination behavior between unbound aggregate layer and asphalt mixture overlay based on the finite difference and discrete element coupling method

AbstractThe constraint action of the unbound aggregate layer underneath plays an important role in affecting the temperature strains in the top asphalt layer. The focus of the present paper is to investigate the interactive thermal contraction mechanisms between the asphalt mixture and granular base layers to offer a new perspective in promoting the understanding of the thermal cracking disease. In this paper, both experiments and simulations were conducted for the thermal contraction tests. A novel numerical modeling of virtual composite structures was proposed using wall‐zone coupling operation based on the finite difference and discrete element coupling method. The experimental composite structures containing three types of asphalt mixture overlays and five types of unbound aggregate base layers were developed for verification. The thermal contraction and restraint mechanism were revealed from both macro and microscopic scales. The proposed numerical modeling shows a 94% high accuracy. The particle displacement vector and contact force chain could explain the thermal contraction behavior of composite structures. Smaller particle motion displacement or stronger contact force chain result in a higher restraint strain of the asphalt overlay. The thermal contraction behavior can be coordinated through the compaction and loosening of unbound aggregates. The material parameters and cooling temperature differences in the asphalt overlay have slight effects on the constraint action of a base layer, while the gradation and mechanical parameters of the unbound aggregate layer show significant impaction. The parameters, cohesion C and friction angle φ, show a quadratic function with the restraint coefficient. This work has significant guidance on the selection of pavement structure and materials to improve the thermal cracking problem and lay the basis for the mechanical theoretical calculation to predict thermal cracking.

Mechanical Behavior of Bio-Inspired Honeycomb-Core Composite Sandwich Structures to Low-Velocity Dynamic Loading.

In order to improve the impact resistance of sandwich panels under low-velocity impact, the lotus leaf vein is selected as a biological prototype to design a bio-inspired honeycomb (BIH) sandwich panel. ABAQUS is used to establish and effectively verify the finite element (FE) model of the BIH sandwich panel. To systematically compare and study the mechanical properties of BIH and conventional hexagonal honeycomb sandwich panels under low-velocity impact, the maximum displacement of face-sheets, the deformation mode, the plastic energy consumption and the dynamic response curve of the impact end are presented. At the same time, the performance differences between them are revealed from the perspective of an energy absorption mechanism. Furthermore, the influence of the circumscribed circle diameter ratio of the BIH trunk to branch (γ), the thickness ratio of the trunk to branch (K) and the impact angle (θ) on impact resistance is studied. Finally, the BIH sandwich panel is further optimized by using the response surface method. It can be concluded that, compared to conventional hexagonal honeycomb sandwich panels, the addition of walls in the BIH sandwich panel reduces the maximum deformation of the rear face-sheet by 10.29% and increases plastic energy consumption by 8.02%. Properly adjusting the structural parameters can effectively enhance the impact resistance of the BIH sandwich panel.

Test Setup for Investigating the Impact Behavior of Biaxially Prestressed Composite Laminates

AbstractInstrumented impact testing and compression-after-impact testing are important to adequately qualify material behavior and safely design composite structures. However, the stresses to which fiber-reinforced plastic components are typically subjected in practice are not considered in the impact test methods recommended in guidelines or standards. In this paper, a test setup for investigating the impact behavior of composite specimens under plane uniaxial and biaxial preloading is presented. For this purpose, a special test setup consisting of a biaxial testing machine and a specially designed drop-weight tower was developed. The design decisions were derived from existing guidelines and standards with the aim of inducing barely visible impact damage in laminated carbon fiber-reinforced plastic specimens. Several measurement systems have been integrated into the setup to allow comprehensive observation of the impact event and specimen behavior. A feasibility test was performed with biaxially prestressed carbon fiber-reinforced plastic specimens in comparison with unstressed reference tests. The compressive-tensile prestressing resulted in lower maximum contact forces, higher maximum deflections, higher residual deflections and a different damage pattern, which was investigated by light microscopic analysis. Finally, the functionality of the experimental setup is discussed, and the results seem to indicate that the test setup and parameters were properly chosen to investigate the effect of prestresses on the impacts behavior of composite structures, in particular for barely visible subsequent damages.

Computational Modelling and Analysis of Effect of Viscoelastic Materials on Damping and Vibrational Behaviors of Composite Structures—An Extensive Review

Computational Modelling and Analysis of Effect of Viscoelastic Materials on Damping and Vibrational Behaviors of Composite Structures—An Extensive Review

In-plane compressive strength and failure behaviors of composite sandwich structures for wind turbine blades

Composite sandwich structure, as the largest part of wind turbine blades, often experiences complex failure phenomena during full-scale blade testing and wind farm operation. In order to better understand failure behaviors and reveal the failure mechanism of sandwich structures for wind turbine blades, composite sandwich samples were designed, fabricated, and tested in consideration of the real laminate and core machining configuration, manufacturing process, and dominating load of wind turbine blades, In-plane compressive strength and failure behaviors were investigated by experimental and theoretic methods. It was found that the grooved with perforations and cut (GPC) machining configuration can improve in-plane compressive strength of sandwich samples more than that of the double grooved with perforations (DGP) configuration due to higher core shear modulus, the failure mode of sandwich samples shifted from global buckling for Plain configuration to a combination of core shearing and skin/core debonding at both sides for DGP configuration, and finally to skin/core debonding at the shallow groove core side for GPC configuration. The failure mode of sandwich samples with DGP core mainly transferred from global buckling to a combination of core shearing and skin/core debonding at both sides, and further to skin/core debonding at both sides alone with increasing foam density. All samples with GPC core exhibited skin/core debonding at the shallow groove side after slight buckling, which was driven by the asymmetric structure of the GPC core. Classical methods can reasonably predict failure loads of sandwich samples with Plain and DGP cores, but overestimate that of sandwich samples with GPC core.

The collapse behavior of cold-formed steel composite beam structure

The innovation of cold-formed steel increases along with the development of sustainable development principles that prioritize eco-friendly, practical, and economical materials. This material, being recyclable, practical, lightweight, and durable, also has the disadvantage of a thin profile thickness, so that it is prone to buckling. In this study, an experimental study was conducted related to cold-formed steel composite beams with concrete material that also contained cavities to reduce the weight of the beams. The specimens are concrete and have a double canal profile of C80.30.9 with a profile thickness of 0.75mm. The connections are made using SDS 12x20 screw connections with a spacing of 150, 200, and 300 mm. The beam span is subjected to concentrated load until the structure collapses. From this research, it was found that collapse from the flexural beam is caused by cracks due to bending moments or bending collapse. The depth of the crack that occurs beyond the cold-formed steel inside the concrete.

3D printed bio-inspired self-similar carbon fiber reinforced composite sandwich structures for energy absorption

Fractals widely found in nature possess amazing simple shape cell yet infinitely complex macrostructures. Importantly, all fractals manifest a degree of self-similarity that provides new structural design strategy for composite materials. At present, enhancing energy absorption capacity of lightweight carbon fiber reinforced composite structures is critical for their further engineering applications, and meanwhile biomimetic structures have demonstrated excellent mechanical properties compared to conventional engineering structures. In this work, we constructed bio-inspired fractal structures through three fundamental shape units (curve, circle, and hexagon), and investigated nonlinear mechanical responses of hierarchical self-similar structures inspired by snake-like serpentine, bamboo, and honeycomb, having distinct structure ratios related to cell sizes at different geometry levels. Firstly, such self-similar structures were fabricated into homogenous ones by 3D printing for assessing the energy dissipation contribution of polymer matrix. Moreover, the selected self-similar carbon fiber reinforced composites were additively manufactured and their energy absorption mechanisms of composite sandwich structures were studied via experiment and numerical methods. Additionally, the influences of the self-similar types, structure ratios, and cellular scales on nonlinear compressive behaviors of self-similar composite structures were investigated in detail. The results indicated that the fractal bamboo composite components with the structure ratio of 0.2 exhibit the highest energy absorption rates, with a satisfactory level of energy absorption capacity in potential engineering applications. This study can provide a useful reference in the field of biomimetic fractal design of fiber reinforced composite structures by 3D printing technique.

Theoretical solution for bond-slip behavior of composite structures consisting of H-shape beam and concrete based on experiment, numerical simulation, and theoretical derivation

This paper presents a theoretical solution for bond-slip behavior of SRC interface based on experiment, numerical simulation, and theoretical derivation. Push-out tests of five specimens were firstly carried out, based on which, the simplified bond-slip model was proposed. The specimen was fabricated using the Q345H-shape steel (400 mm × 200 mm×13 mm × 8 mm) and C50 concrete (350 mm × 600 mm) with a bonding length of 500 mm. A FE model was established based on the bond-slip model to analyze the nonlinear bonding stress that are difficult to obtain from the experiment. The research shows that although the bonding stress in the elastic stage is not uniformly distributed, it is basically uniformly distributed when the ultimate bearing capacity is reached. It proves that assuming the average interfacial bonding stress under ultimate load to replace the maximum bonding stress is reasonable, which is crucial for designer to estimate interface bearing capacity and maximum bonding stress. Moreover, five different stages were obtained by the FE model analysis and the theoretical equations of bonding stress nonlinear distribution were obtained based on the boundary condition of each stage. The theoretical solution clearly showed the relationship between interface nonlinear stress distribution and influencing parameters including the bond area, elasticity modulus of material, section area of specimen, bond-slip constitutive model, and the external load. Based on the theoretical model, the influences of different parameters can be directly obtained without conducting further experiments and establishing different FE models.

Behaviour of soil-steel composite structures during construction and service: a review

Behaviour of soil-steel composite structures during construction and service: a review

Enhanced Reverse-Engineering Method for Accurately Predicting Lamina Properties in Laminated Composites via Combined Static and Dynamic Finite Element Simulations

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.

Experimental and Numerical Analysis of Aluminum-Polyethylene Composite Structure Subjected to Tension and Perforation Under Dynamic Loading for a Wide Range of Temperatures

The aim of this work consists of identifying the material behavior of Alucobond composite structures subjected to ballistic impact. The composite is made of Aluminum alloy AW5005 and LDPE (low-density polyethylene). The mechanical properties of these materials are described in term of strain rate and temperature dependencies. Quasi-static tensile and compression tests for Alucobond are performed at four different strain rates, i.e. 0.0001 0.001, 0.01, and 0.03 s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${s}^{-1}$$\\end{document}. Moreover, in dynamic regime the used strain rate ranges in compression and perforation tests are (104\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{4}$$\\end{document}s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${s}^{-1}$$\\end{document} ≤ ε˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{\\varepsilon }$$\\end{document} ≤ 105\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{5}$$\\end{document}s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${s}^{-1}$$\\end{document}) at temperatures ranging from room temperature 20 °C to 100 °C. Various parameters influence the behavior of the Alucobond structure under impact: the geometry and the mechanical properties of the projectile, the initial impact velocity, and the thermomechanical behavior of the target. Numerous quasi-static and dynamic original test results (traction and perforation over a wide range of strain rates at room temperature and high temperature) are presented. Numerical simulations, particularly using the finite element (FE) method with the ABAQUS explicit code, are also effective supplements for theoretical and more detailed experimental investigations, which were carried out to analyze the dynamic behavior of impacted structures.

Effect of shell spacing on mechanical behavior of multi-span soil-steel composite structure

This study analyses the effect of lateral shells on central shell at a different spacing in a multi-span soil-steel composite structure subjected to quasi-static moving loads. The displacements and internal forces of the central shell during consecutive truck passages over the structure are investigated by finite element (FE) analysis. Field measurements from a site in Niemcza, Poland, are used to calibrate input parameters. Next, the simulations for different spacing between the shells are investigated. The backfill soil is modeled as elastic-perfectly plastic, while the shells and sheet piles are linear elastic. The non-linear contact zone between the shell and the soil backfill is assumed to reflect an elastic-plastic constitutive model. The analysis reveals that both vertical and horizontal displacements increase significantly when the ratio of shell spacing to span length is less than 0.5. Maximum stress occurs when the shells are placed adjacent to each other, i.e., without spacing. The stress is almost doubled in this position compared to the reference case—a single-span structure. The shifting of extreme deflections and stress is observed in the direction of truck movement. Nevertheless, the influence of lateral shells on the central shell's performance under moving loads is nearly negligible when the spacing-to-span ratio exceeds 0.5.

Nanoscale Insights into the Mechanical Behavior of Interfacial Composite Structures between Calcium Silicate Hydrate/Calcium Hydroxide and Silica

The failure of the interfacial transition zone has been identified as the primary cause of damage and deterioration in cement-based materials. To further understand the interfacial failure mechanism, interfacial composite structures between the main hydration products of ordinary Portland cement (OPC), calcium silicate hydrate (CSH) and calcium hydroxide (Ca(OH)2), and silica (SiO2) were constructed while considering their anisotropy. Afterwards, uniaxial tensile tests were conducted using molecular dynamics (MD) simulations. Our results showed that the interfacial zones (IZs) of interfacial composite structures tended to have relatively lower densities than those of the bulk, and the anisotropy of the hydration products had almost no effect on the IZ being a low-density zone. Interfacial composite structures with different configurations exhibited diverse nanomechanical behaviors in terms of their ultimate strength, stress–strain relationship and fracture evaluation. A higher strain rate contributed to a higher ultimate strength and a more prolonged decline in the residual strength. In the interfacial composite structures, both CSH and Ca(OH)2 exhibited ruptures of the Ca-O bond as the primary atomic pair during the tensile process. The plastic damage characteristics of the interfacial composite structures during the tensile process were assessed by analyzing the normalized number of broken Ca-O bonds, which also aligned with the atomic chain break characteristics evident in the per-atom stress map.

A dovetail core design for joints in composite sandwich structures

The increase in the size of composite sandwich structures requires the introduction of core splices to join various segments. In this study, a novel core splice joint configuration is studied and proposed for composite sandwich structures of thick aluminum-based honeycomb core and facesheets made from carbon fibers and epoxy matrix. Experimental and numerical efforts investigate the impact of dovetail joints with different tenon angles on the auxiliary behavior of composite sandwich structures. The results are compared to conventional or straight-core splices without dovetail features. The core-splice interaction with the complete mechanical behavior of the system was assessed by subjecting the fabricated specimens to combinations of bending and shear forces. Additionally, 3D-finite element models compared normal and shear stresses in the splice material and the core/splice interface among the dovetail configurations considered. The study shows that depending on the dovetail joint detail, an ultimate strength increase between 13 and 51% is achieved compared to the strength from currently used straight joints. In terms of toughness, the dovetail specimens show a 2% to 35% higher toughness compared to the standard straight joints.