Modeling Of Composite Structures Research Articles

Marital Satisfaction: Toward an Integrated Understanding. Structural Equation Modelling Helps Unravel the Complexity of Factors that Impact Marital Success

A data set of 1030 individuals (including 392 married couples) was employed to create a comprehensive picture of the interactive impact of many variables on marital satisfaction. Predictor variables were eventually combined into 20 composite variables and structural equation modeling resulted in 78.6% of the variance in marital satisfaction being explained for men; 79.8% for women. The primary dependent variable was Relational Satisfaction. Primary predictors (all composite variables) included emotional engagement, emotional-regulation skills, destructive interactions, shared activities, family and friend support, compatibility, strength of personal identity, accuracy of perception (of their partner), personality traits, temperaments (from the DISC measure), improvement over time, and positive illusions. To measure change over time, participants answered questions for both “now” and in the “first year of marriage”. Further, a criss-cross technique (rate self and partner across all variables) facilitated many comparative predictors. The structural models found the primary predictors of relational satisfaction (with only minor differences between mens’ and womens’ models) to be: emotional engagement (with β values of .56 for both), family and friend support, improvement over time, accuracy of perception, (absence of) destructive interactions, compatibility and positive traits. Equally important were predictors of emotional engagement—the greatest predictor of relational satisfaction: emotional-regulation skills (men), emotional-regulation skills (women), shared activities, accuracy of perception, family and friend support, and looking for the good explained 75% of the variance in the emotional engagement.

Numerical simulation of composite grid sandwich structure under low-velocity impact

Abstract The low-velocity impact finite element model of the carbon fiber-reinforced composite grid sandwich structure was established by ABAQUS. Its panels and grid are both carbon fiber-reinforced composite laminates. The constitutive relation of composite laminates is written into the VUMAT user subroutine using the Fortran language. Simulation of intralaminar failure behavior of composite laminates using the three-dimensional Hashin failure criterion. The quadratic stress criterion and the B-K energy criterion were used to simulate the interlaminar failure behavior, and the delamination damage of the composite panel and the interface debonding damage were simulated. The finite element models of four different types of composite grid sandwich structures, including quadrilateral configuration, triangular configuration, mixed configuration, and diamond configuration, were established. The influence of the single grid width and the height of the grid on the impact resistance of each composite grid configuration was studied. Compared with other geometric configurations, triangular grid sandwich structure provides the best energy absorption characteristics, and T-6-10 has the highest fracture absorption energy (15816.46 mJ). The damage propagation law of carbon fiber-reinforced composite grid sandwich structure under impact load is analyzed.

The NH2-UiO-66/3,4,9,10-perylenetetracarboxylicdiimide for Cr(VI) reduction: DFT calculation, performance, and mechanism

The composite molecular structure model of NH2-UiO-66/PDINH (UiOxPDy) constructed from NH2-UiO-66 and PDINH (3,4,9,10-perylenetetracarboxylicdiimide) was built to conduct density functional theory (DFT) calculations for predicting the heterojunction type and corresponding Cr(VI) reduction reaction mechanism. The results of DFT calculations illustrated that Z-scheme heterojunction interface was inclined to form between NH2-UiO-66 and PDINH via automatically matching the dominant crystal plane, which was in consistent with the results of X-ray photoelectron spectroscopy. Subsequently, the Z-scheme heterojunction UiOxPDy composites (x, y represented the mass of NH2-UiO-66 and PDINH, respectively) were fabricated via ball-milling treatment, which were used to accomplish effective photocatalytic Cr(VI) reduction under low power LED visible light. The as-prepared optimal UiO125PD75 composite demonstrated good stability and reuse performance in the five runs’ successive operations. The corresponding Cr(VI) reduction mechanism over UiO125PD75 was verified with the aid of electrochemical test, radical scavenging experiments and electron spin resonance.

Optimization of the Injection and Physical Properties of Sulfoaluminate Cement via the In Situ Polymerization of Acrylamide

Deep coal mining requires grouting to reinforce the coal rock walls. The conventional polymer-modified cement-based grouting materials have improved toughness but poor fluidity. The purpose of this paper was to improve the injectability of grout. The preconditions were that the physical properties of the stones are not obviously damaged and the mechanical properties are optimized. The acrylamide monomer was incorporated into the sulfoaluminate cement-based grouting material system. The effects of the in situ polymerization modification of the acrylamide on the paste properties and stone body strength were investigated. The results showed that the acrylamide mixed with the sulfoaluminate cement could increase the fluidity of the grouting material, prolong the paste setting time, and improve the flexural strength of the stone body. Compared with the blank group, the 500 mL efflux time of the 1006 mud viscometer in the 35% AM (acrylamide) dosing group decreased from 51 s to 41 s, the initial setting time increased from 15 min to 98 min, and the flexural strength at three days increased by 202.8%. The compressive stress–strain of the stone body gradually changed from brittle to ductile damage as the acrylamide dosing increased. Based on the microscopic analysis, a composite structure model of the inorganic skeleton of the flexible polyacrylamide network of toughened AFt (ettringite) was built in this paper. A mechanical study of the compressive stress–strain characteristics of the stone body was performed. It was concluded that the acrylamide in situ polymerization-modified sulfoaluminate cement-based grouting material is suitable for coal rock wall grouting reinforcement.

Mechanical properties of the composite lattice structure with variable density and multi-configuration

A new composite lattice structure is proposed by combining variable density and multi-configuration arrangement. The parameter mapping model is established, and three composite lattice structure models are presented. The samples are prepared by the additive manufacturing technology SLS (Selective Laser Sintering) with Nylon PA6. The samples are tested by the universal testing machine and drop weight impact testing system. The load-deformation, equivalent impact load and failure mode are analyzed. The results show that compared with the variable density lattice structure, composite model 1 (GBCC cells in the low-density region are replaced by ECC cells) improves the thin rods in the low-density region, composite model 2 (the cell sizes in the high-density region are increased while GBCC cells in the low-density region are replaced by ECC cells) increases the equivalent bending stiffness by 8%, enhances the bending and impact deformation resistance of materials, and composite model 3 (GBCC cells in the high-density region are replaced by BCCxy cells) increases the failure load by 77%, reduces the equivalent impact load by 47%, and improves the toughness and cushioning performance of materials. This work finds that the composite lattice structure with variable density and multi-configuration further improves the mechanical property of lattice materials.

The impact responses and failure mechanism of composite gradient reentrant honeycomb structure

The carbon fiber reinforced composite reentrant honeycomb structures with different gradient distributions of wall thickness were manufactured by mold hot pressing and bonding technology. The dynamic responses of composite gradient reentrant honeycomb structures under local impact load were investigated. The impact process and failure behavior of composite gradient reentrant honeycomb structures under local impact load were obtained through the foam aluminum projectile impact experiment. The influence of wall thickness gradient form on the impact resistance of composite reentrant honeycomb structure was analyzed. The results showed that the wall thickness gradient setting of the reentrant honeycomb structure could reduce the maximum transverse deformation of the rear panel, and improve the anti-impact ability of the structure compared with homogeneous reentrant honeycomb structure. In addition, compared with the positive gradient reentrant honeycomb structure, the negative reentrant honeycomb structure had better impact resistance, and the impact resistance advantage became more obvious with the increase of the impact strength. The finite element model of composite gradient reentrant honeycomb structure under local impact load was presented, and the dynamic responses and failure modes of the numerical simulation results were compared with that of the experimental results.

Uncertainty analysis based on reduced-order models for composite structures with interval field variables

Composite structures exhibit significant spatial variabilities in their response due to the variations in the individual lamina properties. Considering the difficulty of obtaining accurate probability distributions of laminae properties in practical engineering, interval fields are proposed as a beneficial supplement to random fields and a novel uncertainty analysis method has been developed for composite structures. This study focuses on the development of model order reduction strategies to reduce the dimensionality of the problem and achieve faster computations. First, the bounds and autocorrelation are quantified based on measurement data of interval fields, which are expressed as interval Karhunen-Loève expansion. Next, considering the multilayer structure of the laminate, an equivalent reduced-order model is developed to reduce the computational cost. The specific focus of this strategy is on the equivalence of the constitutive matrix on the fine-scale and coarse-scale models, while the reduced-order model is constructed directly based on the data of the constitutive matrix. Finally, the results of the numerical examples present that the proposed reduced-order model can accurately predict the uncertainty response and significantly improve the convergence speed of the interval Monte Carlo results in the uncertainty analysis of composite structures.

Multiscale finite element simulation of mechanical properties of pillared graphene sheet reinforced composites

This article presents a detailed study of the elastic properties of pillared graphene sheet (PGS) reinforced composites. Modeling of several different composite structures using the numerical simulation software ABAQUS. The effects of carbon nanotube pillar distance (PD), pillar length (PL), CNT inclination angle, the volume fraction of PGS and the number of carbon nanotubes per layer in the PGS on the elastic properties of the reinforced composites are analyzed. The simulation results show that as the volume fraction of PGS increases, the Young's modulus E and shear modulus G of the reinforced composites also increase accordingly. The results also illustrate that the Young's modulus E and shear modulus G of the composites decrease as the tilt angle of the CNTs become larger, but increase with the content of CNTs per layer in the PGS. In addition, the PD and PL of CNTs also influence the elastic properties of the composites.

Multiscale thermoelastic modelling of composite strands using the “fundamental solutions” method

A novel computationally effective approach to multiscale thermoelastic modelling of composite structures and its application to a thermomechanical analysis of two ITER superconducting strands is presented. Homogenisation and recovering problems are solved by means of the “fundamental solutions” method, which was expanded to the case of thermoelastic analysis. We describe a general procedure of multiscale analysis on the basis of this method and apply it to recover stresses at the microscopic scale of a composite strands using a two-level procedure. The recovered micro-stresses are found to be in good correlation with the stresses obtained in the reference problem where the entire composite structure was modelled with a fine mesh.

An efficient Bi-level hybrid multi-objective reliability-based design optimization of composite structures

This paper presents computationally an efficient multi-objective reliability-based design optimization (RBDO) method for composite structures with uncertain design parameters. The approach adopted is based on a novel hybrid decomposing-based multi-objective particle swarm optimization and sequential quadratic programming algorithms, which is coupled with bi-level modelling and optimization strategy of composite structures and RBDO using Cross entropy method. The reliability analysis considers the rare-event corresponding to the limit states, which is based on Tsai-Wu failure index. In addition, the growing requirements for composite structural design with a minimum weight, introduces significant research challenges in the RBDO approach as the weight and reliability are the two important opposing design requirements. To address this research challenges, the proposed approach involves both reliability and weight as objective functions. A laminated composite plate and benchmark problems were used to demonstrate the efficiency and accuracy of the proposed method. Results show that the proposed method provides computationally efficient and accurate evaluations of the performance of the design of composite structures in comparison to the conventional Monte Carlo simulation method and can provide a potential for solving large-scale multi-objective RBDO of composite structures design problems.

Stochastic higher-order three-scale strength prediction model for composite structures with micromechanical analysis

Stochastic multiscale modeling and analysis for the strength prediction of composite structures with complex multiscale random configurations remain a challenging problem. This is mainly due to the high-dimensional physical properties, the non-linear and non-Gaussian features, and the fact that many repeated evaluations of the corresponding stochastic multiscale model are often required. In this paper, we develop a stochastic higher-order three-scale strength prediction (SHTSP) model for composite structures, which is designed to overcome the limitations of prohibitive computation involving the microscale, the mesoscale, and the macroscale. By virtue of asymptotic homogenization theory and micromechanical analysis, the SHTSP model is established from the detailed stochastic higher-order three-scale homogenization analysis implemented with analytic solutions of typical composite structures subjected to tension, bending, and twist loads. The SHTSP model represents strength anisotropy through different strength criteria for evaluating the yield state of the different component materials of composite structures, which are induced by material interface deboning or matrix cracking in multiple scales. Moreover, these are constructed and calibrated from the high-accuracy mechanical analysis with help of two classes of mesoscopic and microscopic auxiliary cell functions, respectively. The corresponding numerical algorithm of the SHTSP model and a preprocessing multilevel strategy is designed to improve the computational efficiency. Finally, the numerical experiments in 3D cases illustrate the outstanding performance of the proposed SHTSP model, and the proposed method can significantly reduce the computational time.

Enhancement of vibration attenuation and shock absorption in composite sandwich structures with porous foams and surface patterns

In the present study, composite sandwich structures were investigated to evaluate the effects of porous foams and surface patterns on structural stability and mass reduction of the composite sandwich structures. The composite structures used in the experiments consisted of three layers; the top and bottom polycarbonate (PC) layers and the core porous foam layers. Copper, nickel, and polypropylene (PP) foams were considered in the modeling of composite structures. Laser cutting technology was applied to the top PC layers of the composite structures to realize the surface patterns. Impact hammer and mass drop tests were performed on the composite structures to investigate their vibration attenuation and shock absorption performances. Numerous combinations of composite structures were considered by varying the foam materials and layer thicknesses to determine the best configuration. Finite element method (FEM)-based simulations were conducted to verify the experimental results. The results of this study support the implementation of porous foams and surface patterns for the increase in vibration attenuation and shock absorption performance, while achieving mass reduction for various applications in the engineering field.

Special Issue on Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures

The advancement in manufacturing technology and scientific research have improved the development of enhanced composite materials with tailored properties depending on their design requirements in many engineering fields, as well as in thermal and energy management [...]

Thermal storage achievement of paraffin wax phase change material systems with regard to novolac aerogel/carbon monofilament/zinc borate form stabilization

Recently, the development of thermal conductive phase change composites (PCCs) to overcome the limitation of low thermal conductivity and easy leakage of organic phase change materials (PCMs) has led to the wide application of these materials. In this study, a novolac aerogel-based composite was employed as porous support for the encapsulation of paraffin to fabricate a new class of high-performance PCCs. Carbon monofilaments and zinc borate were incorporated into the aerogel as the heat conduction network. Furthermore, zinc borate can act as a flame retardant and nucleation agent. The nanocomposite aerogels were synthesized using the sol-gel technique and then the molten paraffin was impregnated into systems. The structure and thermal properties of the nanocomposite aerogels and PCCs were characterized. Fortunately, no shrinkage was observed during aerogel synthesis. SEM images showed the formation of novolac colloids on the surface of carbon fiber. The presence of conductive fillers results in an enhancement of the thermal conductivity of novolac aerogel. Moreover, the thermal conductivity of fabricated aerogels was predicted using a modified series-parallel model for porous composite structures. Furthermore, more porosity and larger pore size of aerogels by incorporation of filler have led to a significant increase in paraffin absorption capacity. So that the highest impregnation was reached to 364.5 wt% that belongs to AC15Z15 sample. The form-stable PCMs had negligible paraffin leakage upon phase change process (less than 1.4 wt%). In addition, the leakage of PCMs composite was less than 2.59 wt% after heating for 10 h showed outstanding cycle stability of synthesized PCCs. The phase transition temperature and phase change enthalpy of PCCs were in the range of 85–96 °C and 33.94–41.85 J/g, respectively. Moreover, the latent heat of PCCs is in the range of pure paraffin, achieving high energy storage capacity. This type of PCMs system in nanostructure can be used in electrical industry for free cooling of electrical coils in this temperature range.

Stability analysis of the pile-prestressed anchor composite structure based on failure mode

Pile-prestressed anchor composite structure is widely used in retain engineering, whose stability analysis is mainly based on the slip line passing through the bottom of pile. However, the existing stability analysis is unable to comprehensively consider the actual slip line passing through pile body, pile bottom and the soil under pile. Based on multiple failure modes, a stability analysis model of composite structure considering both the effects of prestress and pile body is established, and the dynamic search algorithm for the model is proposed. We compare the proposed model with the software of LIZHENG deep foundation pit and the existing calculation model and find the effectiveness of our model. It is found that the safety coefficient of the composite structure is directly proportional to the prestress, pile length and pile diameter, but inversely proportional to the pile spacing. Meanwhile, the safety coefficient increases firstly and then decreases with the increase of slip line depth. Increasing the prestress of anchor in the middle and lower part of the slope has a more obvious effect on improving the safety coefficient. The proposed stability model and search algorithm can consider multiple failure modes and obtain the safety coefficient. In addition, it can comprehensively evaluate the stability of the pile-prestressed anchor composite structure retaining slope, which has superior application value.

Study on Design Method of Pile Wall Combination Structure in a Deep Foundation Pit Considering Deformation Induced by Excavation

The technology of pile wall combination in a deep foundation pit is a kind of technology to resist soil and water pressure by using the great stiffness of the retaining pile and basement wall. As a part of basement wall, the retaining pile can reduce the thickness of the basement wall. However, the influence of excavation deformation and the interaction mechanism between the retaining pile and basement wall are ignored in the current design theory of the pile wall combination in a deep foundation pit. Therefore, we proposed a composite structure model of an elastic subgrade beam associated with a continuous beam, and introduced an elastic spring to simulate the interaction between the pile and basement wall. The finite difference equation and calculation method were established to figure out the internal force and displacement of the pile wall combination structure, which was able to accurately calculate the internal force and deformation of the retaining pile during the excavation stage. Based on the above results, further investigation was carried on the interaction between the pile and basement wall during the construction and normal service stage of the basement structure. It was concluded that the basement wall could reduce the lateral displacement on the top of the retaining pile caused by removal of the strut and affect the bending moment of the upper part of the retaining pile among the depth of the basement wall. The bending moment of the basement wall was closely related to the deformation of the retaining pile and changes with the working condition. In addition, the results of factor sensitivity analysis showed that the pile-wall relative stiffness ratio, stiffness of the horizontal beam, and slab of the basement had a significant influence on the interaction between the pile and basement wall.

Heat Transfer Model of Composite Multi-Layer Structure Based on the Thermal-Electrical Analogy Method

Heat Transfer Model of Composite Multi-Layer Structure Based on the Thermal-Electrical Analogy Method

Psychosocial Factors Affecting the Association between a Healthy Lifestyle Behavior Intervention and Depressive Symptoms in Low-Income Overweight or Obese Mothers with Young Children: A Mediational Analysis.

Background:Depressive symptoms are particularly prevalent among low-income overweight or obese mothers with young children, indicating the importance of understanding and addressing this serious health condition. Although lifestyle behavior interventions are promising for alleviating depressive symptoms in low-income overweight or obese mothers with young children, mechanisms underlying the association between these interventions and depressive symptoms in this priority population remain unknown.Objective:A secondary analysis of data from a randomized controlled trial that tested a 16-week community-based lifestyle behavior intervention for low-income overweight or obese mothers with young children was conducted to examine whether autonomous motivation, coping self-efficacy, and emotional coping mediated the association between the intervention and depressive symptoms.Methods:The analysis included 338 participants who completed data collection at baseline and immediately after the intervention. Participants responded to validated surveys measuring autonomous motivation, coping self-efficacy, emotional coping, and depressive symptoms. To test mediation effects, composite indicator structural equation modeling was performed adjusting for baseline measures. The proportion of maximum possible (POMP) scores in the outcome variable per unit change in the predictor variables was used to calculate effect size.Results:The intervention alleviated depressive symptoms (B = −2.42, p = 0.015, POMP = −4.31%), and coping self-efficacy negatively and fully mediated the association between the intervention and depressive symptoms (B = −1.42, p = 0.002, POMP = −2.53%). Autonomous motivation and emotional coping were not significant mediators.Conclusions:Interventions aimed to alleviate depressive symptoms in low-income overweight or obese mothers with young children should include strategies to improve coping self-efficacy. However, continued research is needed to identify other mechanisms that may be contributing to the effect of lifestyle behavior interventions on depressive symptoms in this at-risk group. This information can then be used to simplify and strengthen the interventions and potentially lead to effective dissemination and implementation.

Behavioral Factors Influencing the Adoption of 1/2S d/2 Tapping System by Smallholder Rubber Farmers in Moneragala District

The adoption of the 1/2S d/2 tapping system by rubber smallholders is far behind the expectation of the Rubber Research Institute of Sri Lanka in Moneragala District. This study has assessed the behavioral factors that influence the adoption of the 1/2S d/2 tapping system. Data were collected using stratified random sampling. A self-administrated survey was deployed among rubber smallholders (self-tappers) in Moneragala District during 2020. The conceptual model was developed based on the decomposed theory of planned behavior. Study variables were measured using validated research instruments. A two-stage model-building process was applied. The conceptualized model was tested empirically, using partial least square structural equation modeling (SMART- PLS 3.2 version). The composite six-predictor conceptual framework and structural model explained 79% of the variance in the adoption of the 1/2S d/2 tapping system by rubber smallholders. The adoption of 1/2S d/2 by rubber smallholders positively correlated with the behavioral factors, behavioral intention, and perceived behavioral control. There were positive relationships between; compatibility and attitude, relative advantage and attitude, perceived usefulness and attitude, perceived ease of use and attitude, subjective norms and behavioral intention, facilitating condition, and perceived behavioral control. These findings can help boost the behavioral intention of rubber smallholders in Moneragala District in using 1/2S d/2, especially by improving the aspects of attitude and subjective norms of tappers.

Progressive failure model of high strength glass fiber composite structure in hygrothermal environment

In this paper, a progressive damage model considering hygrothermal effect is established. Taking high strength glass fiber composite plate as an example, the progressive damage model of open-hole composite plate is established, and the ultimate tensile and compressive strength at room temperature, dry state and hygrothermal environment are predicted. The model was verified by comparing with the experimental results. The results of numerical simulation and experiment show that the hygrothermal environment has a significant effect on the ultimate strength of open-hole composite plate. The tensile ultimate strength of open-hole composite plate decreases about 39% and the compressive ultimate strength decreases about 35% at 70 °C and equilibrium moisture absorption. The results show that hygrothermal environment has little effect on the tensile stiffness of open-hole composite plate, and the tensile modulus decreases by 6% at 70 °C and equilibrium moisture absorption. According to the numerical results, the hygrothermal environment can shorten the damage propagation process of the open-hole composite plate under tensile load, but does not affect the damage propagation process under compression load. The hygrothermal environment can change the macro failure diagram of the open-hole composite plate under tension from “X” to “I”, but does not affect the macro failure diagram of the open-hole composite plate under compression.