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Additive manufacturing (AM) has inherent mechanical strength inconsistencies when the build orientation changes. To address this issue, theoretical models, including analytical and numerical models, can be developed to predict the material properties of additively manufactured materials. This study develops a systematic finite element (FE)-based multiscale numerical model and simulation process for the polymer acrylonitrile butadiene styrene (ABS). ABS samples are fabricated using fused deposition modelling (FDM) to determine the material properties and mechanical behaviours. For macroscale analysis, good agreement between the numerical and experimental tensile strength of transverse samples proved that the FE model is applicable for applying a reverse engineering method in simulating the uniaxial tension of samples. The FE modelling method shows its capability to consider infill density effects. For mesoscale analysis, two methods are developed. The first method is a representative volume element (RVE)-based numerical model for all longitudinal samples. The second method is analytical and based on the rule of mixtures (ROM). Modified rule of mixtures (MROM) models are also developed, which demonstrate an improvement compared to the original ROM models. The research outcomes of this study can facilitate the AM process of parts in various engineering fields.

Aiming at minimizing the issues associated with the disposal of polymers, in this study, elastomeric materials derived from 100% recycled feedstocks were produced. Residues of polyurethane (PU) foams (from 0 to 100%) were blended with residues of ethylene–vinyl acetate (EVA) derived from the shoe-soles industry (from 0 to 100%) to produce films by hot compression. The experimental values obtained by the characterization of the blends were compared with the predicted values derived from the rule of mixtures. Despite of the two-phase morphology observed, the high correlation between the experimental and predicted values suggest that phase segregation did not have a significant effect on the properties of the blends. Voids were also observed on the PU derived materials, due to the source of PU (foams), which reduced their density and increased the water absorption. Yet, this did not jeopardize the mechanical performance of the ensuing materials. In addition, higher amounts of PU resulted in stiffer materials, while higher amounts of EVA induced higher thermal stability. From the results, it was demonstrated that the PU/EVA blends, produced from 100% recycled feedstock, presented suitable properties to be used in shoe-soles applications. published

Strong and tough materials are desired for lightweight, energy efficient applications such as electric cars and aerospace applications. Recently, heterostructures are found to produce unprecedented strength and ductility that are considered impossible based on the materials science in our textbooks. Such superior mechanical properties are enabled by a new scientific principle: hetero-deformation-induced (HDI) strengthening and work hardening. Heterostructured (HS) materials consist of heterogeneous zones with dramatic difference (> 100 pct) in flow stresses. The inter-zone interaction produces back stress in the soft zones and forward stress in the hard zones, which collectively produces the HDI stress. HS materials possess a significant synergistic effect where the integrated property exceeds the prediction by the rule of mixtures. Importantly, HS materials can be produced by current industrial facilities at large scale and low cost. The new materials sciences and promising applications are driving the fast development of the HS materials as an emerging field. There are many fundamental issues that need to be probed so as to effectively design HS materials for superior properties. To solve these issues, it requires collaborative efforts by the communities of experimental materials science and computational material science and mechanics.

Two bulk cermets TiC–WC–Cr3C2–(Ni80Cr20)–Mo–2.8C after liquid-phase sintering at 1400°C for 1 h were used to manufacture powders for plasma spraying of coatings. The cermets were fabricated at a limited time of mechanical alloying at the mixing stage. Plasma coatings were sprayed on a setup with a nozzle attached to a plasmatron for local protection of the sprayed particles from the air atmosphere. The WC–Cr3C2–C content in the cermets provided compensation for carbon losses at all stages of coating production and the formation of an annular zone, the volume of which determines the increase in the TiC content in the coatings by 20% and the formation of additional carbides in the matrix. The microhardness of cermet at an initial carbide content of 60% was 15.26–16.83 GPa with a load on the indenter of 200 G and 20.91–24.68 GPa with a load on the indenter of 20 G, and the difference was explained by a scale factor. The contribution of the microhardness of carbides to the microhardness of cermet with an initial carbide content of 60% was estimated according to the rule of mixtures, proceeding from their volume fraction and microhardness of cermet under a load on the indenter of 20 G. In the initial powder for spraying, this contribution is high, 33.19 GPa, close to the hardness of TiC. The contribution of microhardness of carbides in the coating is lower, 28.09 GPa.

In the last decade, single-phase high-entropy materials have attracted considerable research interest owing to their unexpected existence and unique combinations of properties. Recent development of 5-cation high-entropy carbides (HECs) has demonstrated alluring properties compared to the rule of mixtures and binary carbides. Proposed here is the development of ultrahigh-entropy carbides (UHECs) containing 6+ principal elements with greater combinatorial possibilities. The use of 6+ multi-cation compositions allows for the design of ceramics with further tunable properties, while likely possessing higher orders of entropic stabilization. There are 133 possible carbide compositions containing 6, 7, 8, or 9 refractory metal cations in equiatomic ratios. Candidate selection for fabrication and material testing was accelerated using a machine learning model that was originally trained to predict the synthesizability of five cation disordered metal carbides. Two compositions from each category of six through eight cations, one containing Cr and one without, plus the one possible nine cation carbide were fabricated and characterized. The potential for these 6+ cation UHECs as improved materials for oxidative environments is demonstrated by comparing the oxidation performance of a 5- and 7-cation system after 10 min at 1973 K in air. The oxidation behavior is correlated with Ellingham diagrams, and it is demonstrated that the 7-cation carbide has the ability to form a transitional stable 5+ cation HEC layer as elements preferentially form oxides, which results in significantly improved oxidation resistance.

The electrical conduction behavior of solder is well-known, but the dielectric behavior has been reported only recently. Water in the environment commonly affects electronics performance. This work provides the first study of the effect of water on the dielectric behavior of solder (along the solder bar axis). It also provides the first report of a mixed dielectric, which is a new concept referring to the combination of an electronic dielectric and a molecular dielectric. The mixed dielectric here is a combination of Sn-4Ag solder (an electronic dielectric with relative permittivity 3.24 × 106) and water (a molecular dielectric with relative permittivity 80). In this mixed dielectric, the electric field from the high-permittivity solder promotes the electric field in the low-permittivity water, so the relative permittivity of the solder-water combination exceeds that of the corresponding solder-air combination. The relative permittivity of the combination decreases with decreasing solid (solder) volume fraction. For the highest water/air volume fraction in the combination, corresponding to the lowest solid volume fraction of 0.937, the replacement of air with water increases the relative permittivity at 100 kHz by 1.3%, from 3.09 × 106 to 3.13 × 106. The measured relative permittivity is higher than the corresponding calculated value based on the Rule of Mixtures, due to the fringing electric field associated with the water or air, which is not as able as the solder in trapping the electric field in the capacitance measurement using coplanar electrodes.

Improvement of structural efficiency in various materials is critically important for sustainable society development and the efficient use of natural resources. Recently, a lot of attention in science and engineering has been attracted to heterogeneous-structure materials because of high structural efficiency. However, strategies for the efficient design of heterogenous structures are still in their infancy therefore demanding extensive exploration. In this work, two-dimensional finite-element models for pure nickel with bimodal distributions of grain sizes having ‘harmonic’ and ‘random’ spatial topological arrangements of coarse and ultrafine-grain areas are developed. The bimodal random-structure material shows heterogeneities in stress–strain distributions at all scale levels developing immediately upon loading, which leads to developing concentrations of strain and premature global plastic instability. The bimodal harmonic-structure material demonstrates strength and ductility significantly exceeding those in the bimodal random-structure as well as expectations from a rule of mixtures. The strain hardening rates also significantly exceed those in homogeneous materials while being primarily controlled by coarse-grain phase at the early, by ultrafine-grain at the later and by their compatible straining at the intermediate stages of loading. The study emphasises the importance of topological ultrafine-/coarse-grain distributions, and the continuity of the ultrafine-grain skeleton in particular.

The current research is concerned with the small- and large-amplitude free vibrations of a composite beam made of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) media. It is assumed that the beam is operating in a uniform temperature field, which results in thermally pre-buckled or post-buckled configurations. It is further assumed that a three-parameter nonlinear elastic foundation is in contact with the beam during deformation which acts in compression as well as in tension. The elastic material properties of the beam are evaluated by using a modified rule of mixtures scheme which contains efficiency parameters. The thermomechanical properties of the beam are assumed as temperature dependent. The motion equations of the beam are established using three different beam models, namely first-order, third-order, and sinusoidal beam theories. The obtained equations are reformulated using the fact that both ends of the beam are immovable in axial direction. The established equations are transformed into dimensionless presentation. After that, suitable for beams with both ends pinned, with the aid of the two-step perturbation technique, closed-form expressions are provided for small- and large-amplitude free vibrations of FG-CNTRC beams in thermally pre-buckled or post-buckled states. Results of this study are first validated with the available data in the open literature. After that, novel numerical results are provided to explore the effects of geometrical parameters of the beam, foundation stiffness, temperature variation, and different beam theories.

In this research, a method is examined by which the behavior of continuous carbon fiber reinforced additive manufacturing may be simulated using Finite Element Analysis. This technique is used in a...

This research develops an analytical approach to explore the wave propagation problem of piezoelectric sandwich nanoplates. The core of the sandwich nanoplates is a nanocomposite layer reinforced with graphene platelets, which is integrated by two piezoelectric layers exposed to electric field. The material properties of nanocomposite layer are obtained by the Halpin–Tsai model and the rule of mixtures. The Euler–Lagrange equations of nanoplates are derived from Hamilton’s principle. By using the nonlocal strain gradient theory, the nonlocal governing equations are presented. Finally, numerical studies are conducted to demonstrate the influences of propagation angle, small-scale and external loads on wave frequency. The results reveal that the frequency changes periodically with the propagation angle and can be reduced by increasing voltage, temperature and the thickness of graphene platelets.

Equilibrium equations of a rib grid-stiffened composite cylindrical shell reinforced with carbon nanotubes (CNTs) are derived based on the first-order shear deformation theory considering the effect of shear deformation and moment of inertia. The distribution of CNTs across the shell thickness is assumed uniform, and the elastic modulus of the CNT-reinforced polymer is calculated using the rule of mixtures. In order to determine the equivalent stiffness of the grid-stiffened composite cylindrical shell, the smeared stiffness method is used. Equilibrium equations for free and forced vibration of the rib grid-stiffened composite cylindrical shell are solved using the Galerkin method, and the effects of grid ribs on the dynamic response of the shell are investigated. The results found indicate that the use of circumferential ribs in the structure can increase the frequency, change the fundamental mode shape, and reduce the radial displacement by ~ 12% (especially in higher modes). In addition, the results demonstrate that a 5-degree increase in the angle of helical ribs can decrease the radial displacement linearly by 5%. Eventually, the corresponding outcomes reveal that the rib thickness and presence of CNTs may significantly increase the natural frequencies and decrease the radial displacement of such shells.

We characterize the material properties of a woven, multi-layered, hyperelastic composite that is useful as an envelope material for high-altitude stratospheric airships and in the design of other large structures. The composite was fabricated by sandwiching a polyaramid Nomex® core, with good tensile strength, between polyimide Kapton® films with high dielectric constant, and cured with epoxy using a vacuum bagging technique. Uniaxial mechanical tests were used to stretch the individual materials and the composite to failure in the longitudinal and transverse directions respectively. The experimental data for Kapton® were fit to a five-parameter Yeoh form of nonlinear, hyperelastic and isotropic constitutive model. Image analysis of the Nomex® sheets, obtained using scanning electron microscopy, demonstrate two families of symmetrically oriented fibers at 69.3°± 7.4° and 129°± 5.3°. Stress-strain results for Nomex® were fit to a nonlinear and orthotropic Holzapfel-Gasser-Ogden (HGO) hyperelastic model with two fiber families. We used a linear decomposition of the strain energy function for the composite, based on the individual strain energy functions for Kapton® and Nomex®, obtained using experimental results. A rule of mixtures approach, using volume fractions of individual constituents present in the composite during specimen fabrication, was used to formulate the strain energy function for the composite. Model results for the composite were in good agreement with experimental stress-strain data. Constitutive properties for woven composite materials, combining nonlinear elastic properties within a composite materials framework, are required in the design of laminated pretensioned structures for civil engineering and in aerospace applications.

This paper presents a study on the modelling and free vibration analysis of a rotating functionally graded (FG) porous blade-disk-shaft assembly reinforced with graphene nanoplatelets (GPLs) resting on elastic supports. The rotor is made of graphene nanoplatelet (GPL) reinforced porous foam metal matrix. Both uniform and non-uniform distributions of GPLs and pores in the rotating assembly are considered. The effective material properties are thought of as layered change along the directions of blade thickness, disk radius and shaft radius. Moreover, the material values of this functionally graded structure are determined via the open-cell scheme, the Halpin–Tsai model together with the rule of mixtures. According to the finite element (FE) method, the modelling and free vibration analysis of the nanocomposite blade-disk-shaft rotor system is conducted. To verify the present analysis, the experimental method is adopted. The FE results and experimental results have great match with each other. Special attention is paid to the effects of the rotating speed, GPL distribution pattern, GPL weight fraction, length-to-width ratio and length-to-thickness ratio of GPLs, porosity distribution, porosity coefficient and support stiffness. The obtained conclusions can give particularly important suggestions for the design of GPL reinforced porous blade-disk-shaft rotor systems to achieve advanced mechanical performance.

In this study, a simplified approach to correlate the experimental tensile strength values of the randomly oriented short fiber (SF) reinforced polymer-based composites is presented. For this purpose, a constitutive model to correlate the experimental tensile strength values of SF reinforced composites is derived. The constitutive model was derived based on a rule of mixtures. The experimental results on the Short Carbon Fiber (SCF) reinforced composites reported in our earlier works show a non-linear increase in its tensile strength as the fiber volume fraction is increased. The experimental strength of the composite was found to be significantly dependent on the interfacial stress at the fiber–matrix interface and the percentage of fibers oriented in the loading (tensile) direction. Thus, the orientation dependence of the fibers was incorporated by assuming that the percentage of aligned fibers follow the Weibull Probability Distribution Function (PDF). Additionally, the derived constitutive model was verified against the reported tensile strength data of SCF composites. The correlations of the experimental results from our earlier published work and from other available data in the literature, with the proposed model, were found to be in good agreement. The analytical model was compared to other analytical models and found that the current model showed better agreement with the reported experimental results.

Here, we probed the local creep response of SiC/SiC ceramic matrix composites via high-temperature indentation to examine the contributions of heterogeneous microstructure to creep. Indentations were conducted up to 800 °C on single and polycrystalline Si and SiC, reaction-bonded SiC, and the SiC/SiC composite, which indicated higher creep strain rates of polycrystalline materials yet uncovered comparably lower strain rates of the SiC/SiC composite. Indentation creep rate was observed to be highly dependent on contact stresses. An analytical creep model was presented based on a rule of mixtures approach to incorporate material heterogeneity of the SiC/SiC composite. A finite element model was applied to predict the indentation deformation zone, in which the composite constituents would jointly influence the creep response. The analytical model was then solved for temperatures up to 800 °C and exhibited good agreement with experimental measurements.

This study aims to fabricate partially stabilized zirconia (PSZ)-titanium (Ti) composites to produce implants having ceramic and metallic characteristics. To fabricate such materials via powder metallurgy, sintering reactions must be suppressed. In this study, ceramic-coated Ti powder was used as a starting material to suppress Ti oxide formation. Yttria was coated on Ti powder using the sol-gel technique, the Ti powder was mixed with PSZ powder, and the mixed powders were sintered. From the results of optical microscopy and XRD analysis, dense PSZ-Ti composites containing the yttria phase were successfully fabricated without any reaction products. Hardness and bend tests revealed that the hardness and elastic modulus of the composites increased with the increase of PSZ content and agreed with the predicted values based on the rule of mixtures. Bend tests also revealed that the strength did not improve, as the brittle yttria phase preferentially fractured in the composites subjected to bending.

Linear thermo-elasticity equations are derived in this paper for anisotropic, particle-reinforced composite structures at mesoscale. The full set of equations is first derived at microscale where the structure is represented as a three-dimensional body with spherical inclusions of known spatial distribution. Limiting the consideration by infinitesimal strains and assuming that the inclusions are embedded into the body firmly and that there are no any defects at the interface of inclusions, the mesoscale limit of the set of equations is derived as the scale parameter decreases to 0. Convergence of the corresponding solutions is established. Material characteristics at mesoscale are expressed in terms of Dirac distribution corresponding to a structure with point inhomogeneities. It is shown that the effective or macroscale material characteristics evaluated in terms of the mesoscale ones, match the well-known rule of mixtures. A particular case of Ambarcumyan plate with random distribution of spherical inclusions is studied numerically.

This study investigated the dissolution of silk multifilament fibres in the ionic liquid 1-ethyl-3-methylimidazolium acetate. The dissolution process was found to create a silk composite fibre, comprising undissolved silk multi-filaments surrounded by a coagulated silk matrix. The dissolution procedure was carried out for a range of temperatures and times. The resulting composite fibres were studied using a combination of optical microscopy, wide angle X-ray diffraction (XRD) and tensile testing. An azimuthal (alpha) XRD scan enabled the orientation of the composite silk filaments to be quantified through a 2nd Legendre Polynomial function (P2). The P2 results could be shifted to construct a single master curve using time-temperature superposition (TTS). The shifting factors were found to have an Arrhenius behaviour with an activation energy of 138 ± 13 kJ/mol. Using a simple rule of mixtures the P2 measurements were used to calculate the dissolved silk matrix volume fraction (Vm), which also displayed TTS forming a single master curve with an activation energy 139 ± 15 kJ/ mol. The tensile Young’s Modulus of each silk composite filament was measured and these results similarly formed a master curve with an activation energy of 116 ± 12 kJ/mol.

The silicon carbide filler glass fiber reinforced polymer composites have been prepared by using hand- lay- up technique compression molding machine. Thermal conductivity of silicon carbide filler glass fiber reinforced polymer composites at different volume fractions of glass fiber and silicon carbide is determined using Lee’s apparatus experimentally. The experimental results show that the thermal conductivity of the hybrid polymer composite increases with increase in silicon carbide percentage. Experimental results are compared with mathematical models Hashin formula, Maxwell model and Rule of mixture model to find the variation of the thermal conductivity with volume fraction of silicon carbide. All three mathematical models exhibited results close to each other at low percentage silicon content. From mathematical models and experimental results the difference between the two has been found to be small for 20% SiC content; for example, Maxwell model showed a difference 10.40%, Rule of mixtures 16.12% and Hashin formula 3.62% for 20% SiC content.

Composite structures whose characteristic dimensions are found at the nanoscale are called nanocomposites. In this paper, vapor grown carbon fibers (VGCF) are reinforced in a polypropylene matrix, termed as nanocomposites. A square representative volume element (RVE) is taken in this analytical study to predict the storage modulus, loss modulus and strain energy of the nanocomposites. The diameter of the VGCF is 200 nm and length is 3800 nm. A longitudinal loading is applied along the length of the nanofibers to predict the modulus in the fiber directions. However, a transverse pressure is applied on the RVE to predict the modulus in the transverse direction of the fibers. In this work, two types of arrangement of the fibers are taken inside the RVE. These types are VGCF through the RVE and VGCF inside the RVE. Finite element (FE) analysis software termed as nnumerically integrated elements for system analysis (NISA) is used to predict the mechanical properties of the nanocomposites. The predicted results from FE method/strain energy method are compared with conventional rule of mixtures. It is observed that there is considerable improvement in longitudinal modulus of the VGCF/pp nanocomposite for addition of small amount of nanofiber.

The current paper studies the development of new models for the prediction of tensile modulus in metal/carbon nanotubes (CNTs) nanocomposites. Several composite models such as the Hirsch, Hui–Shia, developed Halpin–Tsai for 3D fillers and Lewis–Nielsen models can present appropriate predictions compared to experimental results of a Cu/multiwalled CNTs (MWCNTs) sample. Furthermore, Takayanagi model reveals that the effect of the interface phase should be considered for the present nanocomposite. Therefore, an appropriate evaluation of the thickness and modulus of the interphase is carried out by the Ji model. In addition, new models are developed based on the modified rule of mixtures and Kerner–Nielsen models. Many ineffective and difficultly characterized parameters are eliminated from the suggested models. The developed models demonstrate the best predictability together with significant simplicity for the calculation of tensile modulus in nanocomposites.

In the present work stir casting route is used to fabricate the ZA27 Metal matrix composites containing 3 wt%, 6 wt%, 9 wt%, and 12 wt%. Zircon sand particulates of size 100 mesh. Microstructure studies using Optical Microscopy, SEM-EDAX are carried out to ascertain the distribution and morphology of particulates in the composites. Effect of zircon sand as reinforcement on bulk density, porosity, of the fabricated composites is studied. SEM studies are carried out to understand the behavior of as-cast ZA27 alloy reinforced with zircon sand. The dislocation density of the fabricated composite affects the strength of the composites and depends on the strain due to thermal mismatch and is found to increase with increase in weight% of zircon sand. However, it does not consider casting defects of voids/clustering observed in micrographs of the fabricated composite. Porosity in composites does not have influence on Coefficient of thermal expansion (CTE) of the ZA27 composites studied using thermoelastic models like Kerner and turner model and rule of mixtures of composite.

This work is focused on the static studies on Smart active composites cantilever beams (SACCB) obtained by reinforcing shape memory alloy wires in a polymer matrix. Homogenization is carried out for the composite using the rule of mixtures to obtain effective material properties. Analytical modeling is carried out for SACCB to determine the beam tip deflection. SACCB specimen is fabricated using hand layup process. A suitable die is prepared so that it provides the required pretension in the SAM wires reinforced in SACCB. Experimental studies are conducted on the SACCB in the static cantilever beam condition. A comparison of the analytical and experimental results is presented.

Stanene has revealed a new horizon in the field of quantum condensed matter and energy conversion devices but its significantly lower tensile strength limits its further applications and effective operation in these nanodevices. Van der Waals heterostructures have given substantial flexibility to integrate different two-dimensional (2D) layered materials over the past few years and have proven highly functional with exceptional features, appealing applications, and innovative physics. Considerable efforts have been made for the preparation, thorough understanding, and applications of van der Waals heterostructures in the fields of electronics and optoelectronics. In this paper, we have executed Molecular Dynamics (MD) simulations to predict the tensile strength of van der Waals heterostructures of stanene (Sn) adsorbed on graphene (Gr), hexagonal boron nitride (hBN), and silicon carbide (SiC) (Sn/Gr, Sn/hBN, and Sn/SiC, respectively) subjected to both armchair and zigzag directional loading at different strain rates for the first time, which has enticing applications in electronic, optoelectronic, energy storage and bio-engineered devices. Among all the van der Waals heterostructures, the Sn/SiC heterostructure exhibits the lowest tensile strength and tensile strain. Furthermore, it has been found that zigzag directional loading could endure more tensile strain before fracture. Besides, it has been disclosed that though the rule of mixtures may accurately reproduce the Young's modulus of these heterostructures, it has limitations to predict the tensile strength. Fracture analysis suggests that for the Sn/hBN heterostructure the fracture initiates from the stanene layer while for the Sn/Gr and Sn/SiC heterostructures the fracture initiates from the Gr and SiC layer, respectively, for both armchair and zigzag directional loading. Overall, this study would aid in the design and efficient operation of Sn/Gr, Sn/hBN, and Sn/SiC heterostructures when subjected to mechanical force.

Bending response in smart functionally graded material (FGM) panels is presented using a zigzag theory. The functionally graded panel has sensing and actuation capabilities due to the presence of two piezoelectric layers at its outer surfaces. The theory is capable of predicting structural responses in presence of material property continuity as well as discontinuity at the interfaces. Rule of mixtures is used in obtaining effective material properties across thickness of each layer. Governing equations and boundary conditions have been derived using variational principle. Responses in piezoelectric laminated FGM panels have been analyzed using two smart FGM panels of which one panel contains non-symmetric FGM substrate and the other contains symmetric FGM substrate. Effects of variation of the power law index have been studied in thick and moderately thick multilayered smart FGM panels.

Recent investigations have highlighted the multi-resolution and high throughput characteristics of the spherical indentation experimental and analysis protocols. In the present work, we further demonstrate the capabilities of these protocols for reliably extracting indentation stress-strain (ISS) responses from the microscale constituents as well as the bulk scale of dual phase materials exhibiting bimodal microstructures. Specifically, we focus on bimodal microstructures produced in an α–β Ti6242 sample. Combining the multi-resolution indentation responses with microstructural statistics gathered from the segmentation of back-scattered electron images from the scanning electron microscope allowed for a critical experimental evaluation of the commonly utilized Rule of Mixtures based composite model for the elastic stiffness and plastic yield strength of the sample. The indentation and image analyses protocols described in this paper offer novel research avenues for the systematic development and critical experimental validation of composite material models.

Adhesives are extensively used in the automotive and aeronautical industries as they enable the creation of durable and light weight joints, with exceptional strength to weight ratios. The constant search for the means of adapting the mechanical performance of adhesives to each application has led to the use of several types of fillers to change their properties. Following a study on the effect of inorganic fillers, i.e., hollow glass beads, in the failure mechanisms of single lap joint’s (SLJ), this work focuses on the response of the strength and fracture properties of structural adhesives to this filler. To this end, their tensile strength and mode I fracture properties were thoroughly analyzed by performing bulk tensile and double-cantilever beam (DCB) tests, at a quasi-static speed. The specimens were manufactured by adding different %v/v of filler to two epoxy-based crash resistant adhesives. Both adhesives have shown a negligible effect on the tensile strength, a decrease in strain at failure and critical energy release rate in mode I, as well as an increase of the Young’s modulus, for higher % in volume of hollow glass beads. These phenomena were further analyzed recurring to scanning electron microscopy, and the concept of rule of mixtures.

In the present study, three types of bimetal composites, Al 6082 sleeve/Al 6082 core, Mg AZ31 sleeve/Mg AZ31 core and Al 6082 sleeve/Mg AZ31 core, were fabricated by drilling and assembling. The rule of mixtures (ROM) for the flow curves and yield strengths during compressive test were addressed. Our results show that the ROM can predict well the experimental flow curves and yield strengths of bimetal composites without bonding, irrespectively of the different strain hardening behavior between the two components.

Single fiber-tow minicomposites represent the major load-bearing element of woven and laminate ceramic matrix composites (CMCs). To understand the effects of fiber type, fiber content, and matrix cracking on tensile creep in SiCf/SiC CMCs, single-tow SiCf/SiC minicomposites with different fiber types and contents were investigated. The minicomposites studied contained either Hi-Nicalon™ or Hi-Nicalon™ Type S SiC fibers with a boron nitride (BN) interphase and a chemical-vapor-infiltrated-silicon-carbide (CVI-SiC) matrix. Tensile creep was performed at 1200 °C in air. A bottom-up creep modeling approach was applied where creep parameters of the fibers and matrix were obtained separately at 1200 °C. Next, a theoretical model based on the rule of mixtures was derived to model the fiber and matrix creep-time-dependent stress redistribution. Fiber and matrix creep parameters, load transfer model results, and numerical modeling were used to construct a creep strain model to predict creep damage evolution of minicomposites with different fiber types and contents.

The mechanical behaviour of bamboo is greatly influenced by its transverse properties, which are not easily measured by experiment. This study develops a framework and the computational tools required to evaluate the material and mechanical properties of bamboo in its full-culm form. A numerical model of bamboo as a transversely isotropic material with functionally graded material properties in the radial direction is developed. The random field method was introduced as a means of quantifying the measured uncertainty of bamboo with respect to the mechanical characterisation of its full-culm state. Four increasingly complex approaches to model circumferential compression tests of bamboo are presented: a theoretical evaluation using Castigliano’s theorem; an orthotropic model neglecting the graded nature of the culm wall; and, two models—one discrete and one continuum-based that define a transversely isotropic graded material. Output from each model is compared, calibrated and validated with experimental results. While the models developed were robust, their application has drawn into question the fundamental hypothesis that the functionally graded behaviour of bamboo can be captured using the rule of mixtures.

Zirconium (Zr) partially stabilized zirconia (PSZ) composites were fabricated using the spark plasma sintering technique with the aim of producing medical implants with reduced metal-related artifacts in magnetic resonance imaging. Composites with compositions ranging from 100% Zr to 100% PSZ were fabricated, and they exhibited high mechanical performance. Optical microscopy and density measurements revealed that dense composites were successfully produced, irrespective of the PSZ content. Hardness and bending tests were performed to evaluate the influence of the addition of PSZ on the mechanical properties of the composites. The results showed that the hardness and bending strength increased with increasing PSZ content. The elastic modulus of the composites was higher than that predicted by the rule of mixtures, and this was due to the formation of Zr oxide around the Zr phase during sintering. It was concluded that the mechanical properties of the composites could be controlled within the range of those of monolithic Zr and monolithic PSZ, and that the use of PSZ was effective for improving the mechanical properties.

In this study, the free vibration of a composite sandwich plate reinforced with graphene nanoplatelets (GPLs) enclosed by piezoelectric layers is investigated using an analytical solution. In the framework of the first-order shear deformation plate theory, multilayer functionally graded graphene platelets-reinforced composite plate is assumed. Applying modified Halpin–Tsai model and rule of mixtures, the effective Young’s modulus, mass density and Poisson’s ratio of nanocomposites are predicted. In each individual layer, the weight fraction of GPL nanofillers illustrates a layer-wise variation along the thickness direction either uniformly or non-uniformly GPLs dispersed. Based on Maxwell’s equation, the electric potential in a piezoelectric layer is considered for open and closed circuit boundary conditions. Coupled governing equations of motion and boundary conditions are derived by using the Hamilton’s principle. Four auxiliary scalar functions are introduced to decouple the governing equations of motion and boundary conditions, which are solved analytically by employing Levy-type boundary conditions. The effects of GPLs weight fraction, GPLs distribution patterns, number of layers and aspect ratio are examined in detail. The results show that the best way to predict the most effective reinforcement is to distribute more GPLs with a larger surface area near the top and bottom surfaces of the plate. Besides, adding a small amount of GPLs as reinforcing nanofillers can significantly improve the stiffness of the plate.

A linear free vibration analysis is presented for computing the natural frequencies of a grid-stiffened carbon-nanotube-reinforced composite cylindrical shell. The carbon nanotubes (CNTs) are supposed to be oriented unidirectionally across the shell thickness, and the elastic moduli of the CNT-reinforced polymer composite are calculated using a modified rule of mixtures. In order to obtain the equivalent stiffness parameters of the grid-stiffened cylindrical shell, the smeared stiffness method is employed. The stiffeners are assumed to support the transverse shear loads, bending moments, and axial loads. An analytical method based on the first-order shear deformation theory is used. To validate the results obtained, a 3-D finite-element model is employed using the ABAQUS CAE software.