Modeling Of Composites Research Articles

Computational modeling and multiscale homogenization of short fiber composites considering complex microstructure and imperfect interfaces

Computational modeling and multiscale homogenization of short fiber composites considering complex microstructure and imperfect interfaces

Physics-integrated neural differentiable (PiNDiff) model for composites manufacturing

Various manufacturing technologies are being developed to improve the manufacturing of composites owing to their low weight and high performance. The mechanical properties of the composites depend on various variables and parameters of the manufacturing process, which are challenging, if not impossible, to determine and optimize experimentally. Traditional first-principle modeling approaches are not accessible due to the complex physics involved. A hybrid model that combines incomplete physics knowledge with available measurement data within a differentiable programming framework opens up new avenues to tackle the challenges. In this work, a physics-integrated neural differentiable (PiNDiff) model is developed, where the partially known physics is integrated into the recurrent network architecture to enable effective learning and generalization. The merit and potential of the proposed method have been demonstrated in modeling the curing process of thick thermoset composite laminates, whose governing physics is partially given. The proposed PiNDiff model shows the capability to learn unknown physics from the limited, indirect data and, meanwhile, can be used to infer unobserved variables and parameters. The performance of the PiNDiff model has been compared with two state-of-the-art (SOTA) black-box deep learning models, and its advantages over the purely data-driven models and first-principles physics-based models have been discussed in detail. The demonstrated PiNDiff strategy may provide a general strategy to model phenomena where physics is only partially known and sparse, indirect data are available.

Simulation method of debris cloud from fiber-reinforced composite shield under hypervelocity impact

A Whipple shield is a double-plate structure commonly used to protect spacecraft from space fragments. The space fragments hit the outer plate and break into a debris cloud with dispersed energy and momentum, which reduces their risk of penetrating the bulkhead. With the development of high-performance materials, for example, high-performance fiber composites, traditional Whipple shields have evolved into advanced complex shields. Using the finite element and smoothed-particle hydrodynamics adaptive method and mesoscopic modeling technology, this study aims to establish a numerical model for fiber-reinforced composite shields under hypervelocity impact. Several mesoscale models for fiber-reinforced composites for problems under hypervelocity impact have been established. These models can be meshed with high-quality elements that satisfy aerospace engineering requirements (identify hazardous fragments in the debris cloud) while retaining the main structural features of materials. We established a numerical model by combining the finite element and smoothed-particle hydrodynamics adaptive method and existent mesoscale models. Using laminates, 2D woven fiber-reinforced plastics, and 3D woven fiber-reinforced composites as examples, numerical simulations of the debris cloud generated by an aluminum ball under hypervelocity impact were conducted. The simulation results, which are highly consistent with the experimental results of the debris cloud shape, accurately reflect the failure features of laminates, that is, fiber fracture and delamination. Simulation results show that the fiber-reinforced composite has better protection than the aluminum plate at the same areal density. By comparing the debris clouds generated by the hypervelocity impact on different fiber-reinforced composite shields, it can be argued that composite knit modes strongly affect the protective effect of fiber-reinforced composites. This work shows that the simulation method combining the finite element and smoothed-particle hydrodynamics adaptive method and mesoscopic modeling is a powerful tool for simulating the Whipple shield with a fiber-reinforced composite. More importantly, this method can also be applied to other Whipple shields with complex structures and advanced materials, for example, other composite materials, metal foam materials, and multilayer board protective structures.

Dynamic and Damage Characteristics of Mortar Composite under Impact Load

In the process of underground construction, it is common to spray concrete on the working surface, which will form a concrete-rock composite structure, to achieve the expected reinforcement effect. Compared with pure concrete or rock structures, composite structures have different mechanical properties, energy evolution and damage characteristics. Understanding the dynamic mechanics and damage characteristics of composite structures under impact loads is important to the safety of underground engineering construction. First, dynamic compression tests on different grades of mortar-sandstone composite specimens were carried out by using a Hopkinson pressure bar system to discuss the effect of impact velocities on the mechanical properties and failure modes of composite specimens. The results show that the dynamic peak stress, strain energy density and fragmentation block of the mortar-sandstone composite have an obvious strain rate effect. With an increase in impact velocity, the internal cracks of the sample do not have sufficient time to expand, and the energy absorbed by the sample leads to the continuous initiation of new cracks in the sample, resulting in an increasing damage degree of composite specimens. The increase in mortar strength can significantly increase the peak stress, improve the load-bearing capacity of the sample, and reduce the degree of sample damage. At the same impact velocity, the fragmentation degree of the mortar sample is more severe than that of sandstone, and the mortar sample is broken into powder debris, while the sandstone is broken into fragments. In addition, according to the failure properties of the composite sample, the mortar and sandstone samples are described by different damage models, and the dynamic damage constitutive model of the mortar-sandstone composite is established based on the overlay principle. The dynamic test results were fitted. The research shows that the fitting curves of the model are well fitted with the test curves and that the model accurately reflects the changes in the mechanical parameters of the composite specimens.

Thermal and Mechanical Properties of Plain Woven Ceramic Matrix Composites by the Imaged-Based Mesoscopic Model

The mesoscopic finite element model of ceramic matrix composites is developed by reconstructing computed tomography images. The relationship between microstructure and macroscopic properties and their dispersion are explored. Firstly, a three-dimensional reconstructed computed tomography model was carried out to calculate the orientation of the components. Secondly, the orientation and gray value of images were used to identify the basic structure of composites including fiber tows, matrix, and porosities. Finally, the two-dimensional finite element model was developed to analyze the macroscopic thermal and mechanical properties. The numerical results showed that: (1) the geometries and distributions of pores had a significant effect on the through-thickness modulus and thermal conductivity; (2) the stress and heat flow concentration area on the material surface usually occurred in narrow gaps between closely spaced longitudinal tows; (3) the elastic modulus and thermal conductivity were dispersive, and their distribution followed by two-parameter Weibull distribution.

Microstructure and electrical transport properties of nanoscale [(CO40Fe40B20)34(SiO2)66/(In2O3)/C]46 multilayers

We investigated the role of microstructure and In2O3/C interlayer thickness on the electrical transport properties of [(Co40Fe40B20)34(SiO2)66/(In2O3)/C]46 multilayers prepared using ion-beam sputtering. These multilayers were characterized using an X-ray diffraction, X-ray reflectivity, impedance spectroscopy, and magnetoresistive measurements. The X-ray diffraction data showed that regardless of the layer thickness, all components of the multilayers are X-ray amorphous. Fitting X-ray reflectivity data, multilayer periodicities are extracted and layers thicknesses, densities and roughnesses are determined. Impedance spectroscopy has shown a resistive-capacitive coupling between electrically conductive ferromagnetic CoFeB clusters which corresponds to the model of a prepercolation composite. For the thinnest multilayer with nonmagnetic In2O3/C interlayer thickness of about 1.6 nm, we managed to achieve a magnetoresistance of about 0.8% at room temperature and 3.2% at cryogenic temperature.

Coupled micro-macroscopic modeling of layered composites with finite deformations

A coupled micro- and macroscopic modeling of an incompressible layered composite material under finite deformations is performed based on the asymptotic homogenization method and universal semi-linear models. The deformation diagrams of the periodicity cell are calculated. A method for searching for effective transversally isotropic properties of LCM based on the obtained diagrams is considered. Cylindrical bending of an LCM plate is simulated using the model of a transversally isotropic medium. The microstresses in the periodicity cell are calculated based on the homogenized stresses.

On a computational stress-based non-local damage model for quasi-brittle composites

Numerical models for the stress and strain analysis of quasi-brittle composites, such as cement-based ones, supplied by various stiffening particles, under mechanical, thermal, etc. loads should handle i) the creation of certain micro-damaged zones, antecedent to ii) the initiation and propagation of a system of macroscopic cracks. Whereas ii) can be analysed using some extended, generalized or similar finite element technique (XFEM, GFEM, etc. algorithms), i) must rely on a smeared crack formulation, whose regularization properties are derived from a non-local stress evaluation. This paper studies mathematical and computational properties of such model, based on the Eringen's approach, useful in many applications in civil engineering.

ANALYTICAL MODEL FOR COMPOSITE TRANSVERSE STRENGTH BASED ON COMPUTATIONAL MICROMECHANICS

The transverse strength of fiber-reinforced composites is a matrix-dominated property whose accurate prediction is crucial to designing and optimizing efficient, lightweight structures. State-of-the-art analytical models for composite strength predictions do not account for fiber distribution, orientation, and curing-induced residual stress that greatly influence damage initiation and failure propagation at the microscale. This work presents a novel methodology to develop an analytical solution for transverse composite strength based on computational micromechanics that enables the modeling of stress concentration due to representative volume elements (RVE) morphology and residual stress. Finite element simulations are used to model statistical samples of composite microstructures, generate stress-strain curves, and correlate statistical descriptors of the microscale to stress concentration factors to predict transverse strength as a function of fiber volume fraction. Tensile tests of thin plies validated this approach for carbon- and glass-reinforced composites showing promise to obtain a generalized analytical model for transverse composite strength prediction.

An improved calibration of Karagozian & Case concrete/cementitious model for strain-hardening fibre-reinforced cementitious composites under explosion and penetration loadings

The ultra-high tensile capacity of strain-hardening fibre-reinforced cementitious composites makes them promising for impact dynamics applications, however, there is a lack of reference for taking the parameters of the constitutive model of materials in numerical simulations. In this study, the Karagozian & Case concrete/cementitious model parameters for strain-hardening fibre-reinforced cementitious composites were comprehensively and systematically calibrated. Multiaxial behaviour, crack-bridging constitutive relations, strain-rate effects, regularization of damage evolution parameters, and parameters scaling method for wide-range strength of materials were all considered and carefully discussed. The calibrated parameters were validated using low-velocity drop-weight impact tests, near-field explosion tests, and high-speed penetration tests. In this study, the traditional element erosion method and meshless/particle methods of Smoothed Particle Galerkin (SPG) method were used for failure analysis in penetration and explosion models. The results show that the calibrated parameters accurately predict the cratering and scabbing diameters and failure modes of explosion tests with the element erosion method. Furthermore, the residual velocity of the projectile and crack patterns of targets were also predicted with good precision with both element erosion and SPG methods. However, in the simulations of low-velocity impact tests, the predictions of maximum deflection were acceptable, and the errors in residual deflection were significant due to the inherent weakness of the material constitutive model.

Predicting the tensile stiffness and strength properties of plain woven carbon fiber/epoxy laminates: a practical analytical approach and experimental validations

The difficulties in establishing an analytical model for plain woven fabric composites (PWFC) and its implementation are well-accepted due to the complexity of yarn architecture, approximations assumed, and lack of experimental validations. In this paper, a practical engineering approach is proposed to predict the tensile properties of PWFC. The approach assumes PWFC as cross-ply, the undulation angle an elliptical shape. The approach tremendously simplifies the calculation keeping a close agreement with the tensile experimental results of PWFC. The approach is remarkably compatible with other theoretical models and experiments that existed in the literature.

Finite Element Analysis of Hybrid Skin Sandwich Composite

Sandwich structured composite is a particular classification in composite materials. This type of structure has been mainly used in recent studies because of its high specific strength, low density, and stiffness. It is increasingly more commonly employed in structural designs due to its features and performance. The sandwich composites used in this investigation are made of aluminium alloys and areca fibre. The sandwich composite’s face sheet comes in a variety of thicknesses. The adhesive skin layer is also varied to investigate the effect of using natural fibre. The sandwich composite is subjected to 3 point bend test. The modal analysis is investigated using the finite element method. The 3D model of sandwich composites is modelled using solid works 2020. Using Altair Hyper Works, the boundary conditions and meshing is carried out. ANSYS Mechanical APDL is used to analyse the sandwich composites. This investigation analyses the behaviour of composite sandwich beams.

Interplay of manufacturing-induced thermal residual stresses and microvoids in damage and failure of fiber-reinforced composites

Fiber-reinforced composites have inherent thermal residual stresses (TRS) and microvoids that are both generated during the manufacturing process. While the two factors are naturally included in experimental measurements as they preexist in the specimens for testing, theoretical and computational modeling of composites usually neglect these two or include only one. Such simplifications inevitably introduce errors to the predicted mechanical properties of composites, which may further influence the reliability of subsequent modeling and design efforts. Using a micromechanics-based failure modeling approach, this work investigates the effects of both TRS and microvoids on the mechanical properties of fiber-reinforced composites. The TRS is generated when composites are cooled down from the curing temperature. The microvoids are assumed to take realistically existing circular, triangular, square, and pentagonal shapes. Damage progression is systematically studied in six representative loading modes, five voids, and two TRS conditions. All results are statistically extracted to account for geometric uncertainties. The study unravels the interplay of TRS and microvoids in determining the mechanical properties of composites along with the corresponding failure mechanisms. This investigation provides high-fidelity predictions and theoretical insights to improve our understanding of TRS and microvoids in composites, mitigate their impacts, and guide future modeling and design efforts.

Constitutive model of elastic response for Fe-TiB2 composites

The constitutive model of Fe-based matrix composites to the macroscopic stress was established for revealing the elastic response at multiscale. The effective elastic constants (EECs) of the Fe-TiB 2 composites were predicted by the constitutive model in this study, including the effective elastic modulus E ̅ , effective bulk modulus K ̅ , effective shear modulus G ̅ , and effective Poisson's ratio ν ̅ . And then, the diffraction elastic constants (DECs) related to the crystal planes ( hkl ), ν hkl and E hkl of the constituents of the composites, were also evaluated based on the multiscale correlation constitutive equations. Compared with experimental values, there was excellent agreement for the EECs of the Fe-TiB 2 composites and reasonable errors in DECs of the Fe-based matrixes and TiB 2 reinforcements. Furthermore, the multiscale coupling between the EECs and DECs related to elastic response and residual stress was also concerned in this micromechanical model. The internal stress in the TiB 2 reinforcements is higher than the Fe-based matrixes at the same applied stress of the composites, which means the desired load transfer has occurred.

A viscoelastic-viscoplastic constitutive model for nanoparticle-reinforced epoxy composites: Particle, temperature, and strain rate effects

The mechanical behavior of nanoparticle-reinforced epoxy (NP/epoxy) exhibits highly nonlinear characteristics accompanied by particle, temperature, and strain rate effects, which are of great significance in the study of composites. This study presents a viscoelastic-viscoplastic (VE-VP) constitutive model applied to rigid silica and soft rubber nanoparticle reinforced epoxies (SNP/epoxy and RNP/epoxy), which are subjected to a wide strain rates and temperatures. The proposed constitutive model is based on the decomposition of the Helmholtz free energy into equilibrium and non-equilibrium parts. The equilibrium part employs the hyperelastic strain energy density function to capture the rubbery state property. The non-equilibrium part is decomposed into viscoelastic strain energy density functions and viscoplastic dissipation potential to capture the glassy state behavior. Temperature- and particle- dependent models were introduced into the proposed VE-VP model. To validate the effectiveness of the VE-VP model, the uniaxial compressive responses of the SNP/epoxy and RNP/epoxy were systematically tested. The results demonstrate that the VE-VP constitutive model can capture the nonlinear compressive behaviors of SNP/epoxy and RNP/epoxy over a strain-rate range of 10 − 2 s − 1 to 10 3 s − 1 and a temperature range of − 80 ℃ to 80 ℃ . Finally, the analysis of the model parameters indicates that the strain softening and hardening are strongly affected by the temperature and strain rate. • Two typical nanoparticles (rigid silica and soft rubber) are utilized to reinforced epoxy. • A viscoelastic-viscoplastic constitutive model for nanoparticles reinforced epoxy incorporating the particle, temperature and strain rate effects is proposed. • The compressive behaviors over wide range of temperature and strain rate are experimentally investigated and well predicted by proposed model. • The activation energy and hyperelastic coefficient in proposed model are strongly affected by temperature and strain rate.

Investigation of nanostructured hard metal composites obtained from powder mixtures (WC-Co)-Al2O3

A new stereological model of nanostructured hard metal composites is suggested which describes the packing density, structural parameters and fracture toughness depending on the sizes, volume of the carbides and addition of nanoparticles Al2O3. The results of complex theoretical and experimental investigations of hard metal composites based on powder mixtures (WC-Co)-Al2O3(nano) are presented, which confirm the possibility of improvement of the structure parameters (with the average size of the binder interlayer being up to 0.12 μm and carbide grain up to 1μm), increasing the hardness 15-18 HV, GPa, fracture toughness, K1c, 16-19 MPa m1/2, transverse rupture toughness, σи - 2700 MPa. The results of the modeling experiments are in satisfactory agreement with the measurements of structure parameters and fracture toughness.

Network Optimization of CNT Yarn Sensor Based on NNIA Algorithm in Damage Monitoring of 3D Braided Composites

In order to solve the optimization problem of carbon nanotube (CNT) yarn sensor network embedded in three-dimensional (3D) braided composite materials and realize the structural health monitoring of internal damage of aerospace parts, the multi-objective optimization of the number and location of sensors was studied using non-dominated neighborhood immune algorithm (NNIA). Through the research of 3D six-direction braiding process, stress sensitivity of single CNT yarn sensor, and damage location of 3D braided composites, the number, position, and coverage constraint functions based on NNIA algorithm are constructed. In addition, the number and position of three-dimensional braided composite embedded CNT yarn sensors with different sizes are solved. Through the stress experiment and data analysis of damaged parts, it is proved that the optimized configuration result of CNT yarn sensor obtained by NNIA algorithm is suitable for the damage monitoring of 3D braided composites. The damage location error is less than 1 mm. This study lays a foundation for the establishment of damage source localization model of 3D braided composites.

Study of 1-3 piezoelectric composites based on phononic crystals theory

To further improve the working performance of 1-3 piezoelectric composites, in this paper, they are regarded as two-dimensional phononic crystals, the band structures, transmission characteristics and vibration modes are firstly calculated by the finite element method, and the suppression of lateral vibration by 1-3 piezoelectric composite structure is investigated based on band gap theory to obtain a purer thickness vibration. Secondly, the influence of the lattice system on the band gap as well as the overall working performance of piezoelectric composites is analyzed, finite element models of square and hexagonal lattice piezoelectric composites are established, and their operating parameters such as transmitting voltage response level and total radiated power are calculated by simulation. This study shows that the working frequency of 1-3 piezoelectric composites can be set in the band gap of phononic crystals to obtain better lateral vibration suppression; compared with square lattice, 1-3 piezoelectric composites with piezoelectric phase hexagonal lattice arrangement can obtain larger working bandwidth and higher total radiated power in the thickness mode, the overall working performance is better. This study is a guideline for the design and application of piezoelectric components in the fields of acoustics and medicine.

A microstructure-sensitive and derivative-free continuum model for composite materials: Applications to concrete

Owing to high strength to weight ratio, durability, corrosion resistance and design flexibility, composite materials are extensively used in engineering applications. While these materials have several useful properties, they often exhibit complex failure modes that arise from their heterogeneous microstructure details. A continuum model for composites should accordingly exploit the microstructural information for an accurate prediction of the non-local and non-linear behavior preceding failure. In simulating discontinuities such as cracks, a derivative-free continuum theory – peridynamics, to wit – has an advantage in that the integro-differential balance laws work even with discontinuities. It does not need the special measures required with continuum models using partial differential equations (PDEs) for simulating cracks. In this work, we use a novel non-local variant of the deformation gradient and propose a constitutive model for composite materials within a derivative-free set-up whilst incorporating the microstructural information, which enables a faithful reproduction of the macroscopic response leading to failure. Since concrete is perhaps the most commonly used composite material in large scale engineering applications, we implement the model to study fracture/damage and size effect in concrete. Our results are in close conformity with the experimental data available in the literature. We also show that complex phenomena like crack propagation and branching are accurately simulated via the proposed model with considerably reduced computational overhead.

Preparation and dynamic moisture adsorption of fiber felt/silica aerogel composites with ultra-low moisture adsorption rate

Understanding the effects of preparation parameters on thermal insulation materials is important for reducing building energy consumption. In this study, fiber felt/silica aerogel composites with ultra-low moisture adsorption rate were prepared by the sol–gel and atmospheric drying technology. The effects of relative humidity and preparation parameters (e.g., silica sol ratios, volume ratios of the sol to fiber felt, aging duration, and modification duration) on the performance (thermal conductivity and moisture adsorption rates) of silica aerogel composites were explored. Furthermore, an isothermal adsorption model of silica aerogel composites for water vapor was established. The results showed in the environment with high relative humidity of 90 %, the moisture adsorption rate and thermal conductivity of the composites were approximately 1 % and 0.02 W·m−1·K−1, respectively. However, the moisture adsorption rate and thermal conductivity of the fiber felt were up to 20 % and 0.1687 W·m−1·K−1, respectively. With the change in the sol ratio, the moisture adsorption rate of the composites varied between 0.7 % and 0.8 % after reaching the adsorption equilibrium. The isothermal adsorption process was described by the D–A isothermal adsorption equation with the correlation of more than 0.99. The prepared fiber felt/silica aerogel composites with ultra-low moisture adsorption rate can be widely used for building insulation, especially in humid areas. This study provides the theoretical data reference for applying new aerogel composites insulation materials in high-humidity environments.