Nonlinear Material Research Articles

Wafer-scale fabrication of InGaP-on-insulator for nonlinear and quantum photonic applications

The development of manufacturable and scalable integrated nonlinear photonic materials is driving key technologies in diverse areas, such as high-speed communications, signal processing, sensing, and quantum information. Here, we demonstrate a nonlinear platform—InGaP-on-insulator—optimized for visible-to-telecommunication wavelength χ(2) nonlinear optical processes. In this work, we detail our 100 mm wafer-scale InGaP-on-insulator fabrication process realized via wafer bonding, optical lithography, and dry-etching techniques. The resulting wafers yield 1000 s of components in each fabrication cycle, with initial designs that include chip-to-fiber couplers, 12.5-cm-long nested spiral waveguides, and arrays of microring resonators with free-spectral ranges spanning 400–900 GHz. We demonstrate intrinsic resonator quality factors as high as 324 000 (440 000) for single-resonance (split-resonance) modes near 1550 nm corresponding to 1.56 dB/cm (1.22 dB/cm) propagation loss. We analyze the loss vs waveguide width and resonator radius to establish the operating regime for optimal 775–1550 nm phase matching. By combining the high χ(2) and χ(3) optical nonlinearity of InGaP with wafer-scale fabrication and low propagation loss, these results open promising possibilities for entangled-photon, multi-photon, and squeezed light generation.

Two‐phase flows simulations in a space‐time framework for injection molding applications: Comparison with experimental results

AbstractHigh‐resolution numerical simulations of the injection molding process are crucial for precise process and part behavior prediction and tool fabrication. However, the complex flow behavior with high shear rates, rapid cooling as well as the nonlinear material properties post many challenges, and efficient high‐resolution numerical analysis is still subject to research. This study presents a simplified numerical description of the polymer flow and cooling during the injection phase, aiming for efficient and yet accurate simulations of the process. The in‐house finite‐element solver XNS is used to simulate the polymer and air flows, as a two‐phase flow, using the level‐set method. The injected polymer is characterized as a shear‐thinning flow using the non‐Newtonian Cross‐Williams‐Landel‐Ferry rheology model. To reduce the computational time, other polymer model effects such as a precise crystallization kinetics model during the injection phase have been neglected as a result of the findings of a previous study. Heading towards more efficient computations, we use a space‐time discretization, which has a higher convergence rate than commonly used time discretizations and can allow future mesh refinement in time, particularly convenient for our application. The results of the simulation are compared to the propagation of the flow front in an injection molding process of a plate part. The flow front is traced in‐situ by three aligned infrared sensors that detect the temperature increase from the mold wall. The time of flow front propagation between two sensors is in good agreement with experimental results. The peak temperature is calculated lower as compared to the experiment; however the temperature gradients are in good agreement validating the numerical model presented here.

Integrating simulated and experimental studies on novel single crystal bis(guanidininium) n-carboxylatephenylalanine towards enhanced antitumor effect

A novel organic crystal bis(guanidininium) n-carboxylatephenylalanine (GUPA) was synthesized and X-ray diffraction outcomes exposed P21, triclinic space group with cell dimensions a = 6.6492(3) Å, b = 16.2440(7) Å, c = 7.8985(3) Å, β = 0.127(2) °, V = 853.11(6) Å3, Z = 2 and possess good agreement with experimental data. Intermolecular interactions were revealed through hirshfeld and major contribution from O-H interaction confirms the presence of intermolecular hydrogen bonds. Through B3LYP algorithm with set 6–311++ G (d, p), chemical reactivity forms and molecular structure of GUPA was investigated, confirming a good stability and hard electrophilic nature. While first order hyperpolarizability value (35.37 × 10−31 esu) was indicative of good nonlinear optical material and hyperconjugate interactions and charge delocalization was further confirmed by natural bond orbitals. To further investigate the electronic properties theoretical (TD-DFT) and experimental absorption wavelengths were compared and excitation energies, oscillator strength and type of electronic transition with contributions have also been studied. The topological properties were evaluated using ELF/LOL maps and RDG with NCI were used to establish the type of interaction present in the GUPA molecular system. The anti-breast cancer effect of GUPA was computationally studied through molecular docking against p53 gene and was further investigated through in vitro MDA-MB-231 cell line studies and GUPA showed better inhibition of cancer cells and their expression.

Wind-induced collapse mode and mechanism of super-large hyperbolic steel reticulated shell cooling tower with stiffening rings

With advancement of dry-air cooling technology, it has become feasible to use steel reticulated shell structures in design and construction of industrial cooling towers. Steel reticulated shell cooling towers (SRSCTs) with light weight, high strength, and rapid construction have development potential. Wind-induced collapse accidents in cooling towers frequently occur, characterized by pronounced nonlinear behavior involving significant deformation and material failure. Nevertheless, current stability and collapse analyses of cooling towers based on linear theory and elastic deformation are inadequate and unsafe. Thus, the wind-resistant stability of SRSCTs must be evaluated considering their inherent high flexibility and low damping levels. Considering a 220 m high hyperbolic SRSCT as a case study, a wind-induced collapse FEM simulation and analysis were performed. The average and fluctuating wind loads were measured in a reduced-scale model during wind tunnel tests and used as the time-variant wind pressure in a structural finite-element model. The dynamic performance and buckling collapse analyses of the cooling tower were conducted considering geometric and material nonlinearities. The entire wind-induced failure process of the SRSCT in extreme winds was systematically investigated. The weaknesses in the structural stiffness and the failure process were quantified, with five failure stages and four failure modes. The failure stages included linear elasticity, local member failure, local regional failure, overall structural failure, and collapse. The failure modes included circumferential plastic buckling zone failure, windward buckling failure of the shell, crosswind failure of the stiffening ring (hinged curved-beam mechanism), and windward failure of the stiffening ring (triangular arch-like mechanism). This study confirms that development of plastic buckling zones and formation of plastic hinges, considering geometric and material nonlinearity, are the dominant factor in wind-induced failure and collapse of SRSCTs.

Near-Infrared-II Photoactivated Iron(III) Complexes for Highly Efficient RNS and ROS Synergistic Therapy.

Reactive nitrogen species (RNS) are more lethal than reactive oxygen species (ROS), which gives them a very promising future in the field of cancer treatment. However, there are still a few drugs available for RNS generation. In this work, two 5th-order nonlinear optical materials, FB-Fe(III)/SNP@PEG and FB-Fe(II)-FB/SNP@PEG, are synthesized. The outstanding nonlinear optical properties of FB-Fe(III)/SNP@PEG help to achieve generation of bounteous superoxide anions (O2•-) in deep tissues, while sodium nitroprusside (SNP) provides NO in the body, both of which are prerequisites for RNS generation. Meanwhile, type I and type II ROS were also generated under irradiation of a 1600 nm laser. Based on the synergistic effect of ROS and RNS, FB-Fe(III)/SNP@PEG induced mitochondrial damage and DNA fragmentation and inhibited tumor cells through apoptosis, possessing better therapeutic effects than FB-Fe(II)-FB/SNP@PEG. This work put forward an innovative strategy to achieve the cooperative release of RNS and ROS in deep tissues, which provides insights and ideas for applying nonlinear optical materials to RNS therapy.

Validation of AISI Design of Cold-Formed Steel Beams Using Non-Linear Finite Element Analysis

In the local building industry of Pakistan, pre-engineered steel building manufacturers mainly employ their own self-developed software and Excel sheets. These systems are based on empirical formulas mentioned in the AISI manual. Under this scenario, a need was found to validate AISI flow charts using commercial software like CUFSM 5.04 and ABAQUS R2019x. This study presents a validation of the CUFSM software and the American Iron and Steel Institute (AISI) Direct Strength Method (DSM) results of channel section flexural members using the non-linear finite element method employing ABAQUS. In this study, eight standard cold-formed channel-section (C-section) steel members were modeled and analyzed using ABAQUS to simulate realistic behavior under four-point loading conditions. The non-linear finite element models incorporated material and geometric non-linearities to capture the actual response of the steel elements. The results obtained from ABAQUS were compared with those predicted by the CUFSM and DSM, focusing on critical parameters such as nominal strength, buckling modes, and deformation patterns. During this study, it was observed that out of the selected sections, the AISI charts predict conservative and even unsafe flexural capacities in some of the cases concerning other methods, with a maximum difference of 14.03%. The differences obtained using DSM and ABAQUS when compared with the results of the AISI charts varies on both the plus and minus sides. This study will not only affect the industry in terms of innovative designs for efficient structures but also the community in regards to low-budget construction.

Less is more: surface-lattice-resonance-enhanced aluminum metasurface with giant saturable absorption for a wavelength-tunable Q-switched Yb-doped fiber laser

Resonant metasurfaces provide a promising solution to overcome the limitations of nonlinear materials in nature by enhancing the interaction between light and matter and amplifying optical nonlinearity. In this paper, we design an aluminum (Al) metasurface that supports surface lattice resonance (SLR) with less nanoparticle filling density but more prominent saturable absorption effects, in comparison to a counterpart that supports localized surface plasmon resonance (LSPR). In detail, the SLR metasurface exhibits a narrower resonance linewidth and a greater near-field enhancement, leading to a more significant modulation depth (9.6%) at a low incident fluence of 25 μJ/cm2. As an application example, we have further achieved wavelength-tunable Q-switched pulse generation from 1020 to 1048 nm by incorporating the SLR-based Al metasurface as a passive saturable absorber (SA) in a polarization-maintaining ytterbium-doped fiber laser. Typically, the Q-switched pulse with a repetition rate of 33.7 kHz, pulse width of 2.1 μs, pulse energy of 141.7 nJ, and signal-to-noise ratio (SNR) of greater than 40 dB at the fundamental frequency can be obtained. In addition, we have investigated the effects of pump power and central wavelength of the filter on the repetition rate and pulse width of output pulses, respectively. In spite of demonstration of only using the Al metasurface to achieve a passive Q-switched fiber laser, our work offers an alternative scheme to build planar, lightweight, and broadband SA devices that could find emerging applications from ultrafast optics to neuromorphic photonics, considering the fast dynamics, CMOS-compatible fabrication, and decent nonlinear optical response of Al-material-based nanoplasmonics.

Cubic nonlinearity and surface shock waves in soft tissue-like materials

The cubic nonlinearity of shear wave propagation plays a significant role in brain injury biomechanics. However, soft materials, like the brain, also support the propagation of surface waves, which produce a combination of longitudinal and transverse deformation. The order of the nonlinearity of surface waves in soft materials is still unknown. Here, we directly observe nonlinear Scholte waves propagating in an interface formed by an incompressible gelatin tissue-mimicking phantom and a water layer using ultrasound imaging operated as fast as 16667 frames per second. A two-dimensional correlation-based tracking algorithm was utilized to extract movies of the movement produced by the surface wave. Our results show that the initially nearly monochromatic wave becomes progressively distorted with the propagation due to nonlinearity. The distortion of the wave and its frequency spectrum indicate a high content of odd harmonics when compared with even harmonics. Additionally, by fitting our experimental data to a minimalist one-dimensional model based on the wave speed variation as a function of the perturbation amplitude, we found a cubic nonlinear parameter 46 times larger than the quadratic nonlinear parameter. Overall, the wave distortion, the harmonic development, and the dependence of the wave speed with the amplitude prove that cubic nonlinearity is essential to modeling nonlinear Scholte wave propagation.

Experimental, quantum chemical spectroscopic investigation, topological, molecular docking/dynamics and biological assessment studies of 2,6-Dihydroxy-4-methyl quinoline

The present work is a comprehensive investigation of the spectral, electronic structure, bonding, and reactivity of the 2,6-dihydroxy-4-methylquinoline (26DH4MQ) molecule through a wide range of experimental and quantum chemical spectroscopic calculations techniques, along with its applications as nonlinear optical materials and biological assessments. The study utilized density functional theory (DFT) and time-dependent density functional theory (TD-DFT) with the B3LYP method and the 6-311G++(d,p) basis set to analyze the structural and molecular properties of 26DH4MQ. The findings from UV–Vis, FT-IR, and FT-NMR spectroscopy show a strong agreement between the experimentally obtained vibrational frequencies and chemical shifts and those predicted by computational methods. Local reactivity descriptors, such as the dual descriptor, Fukui functions, and the molecular electrostatic potential (MEP) map, were used to identify the reactive regions of the molecule. Additionally, natural bond orbital (NBO) analysis provided insights into the charge transfer characteristics of 26DH4MQ, which helps to stabilize the molecular system. The study also revealed notable nonlinear optical (NLO) properties, with polarizability (18.52 × 10–24e.s.u.) and first-order hyperpolarizability (2.26 × 10–30e.s.u.) values that surpass those of standard organic compounds, suggesting significant potential for optoelectronic applications. The biological evaluation of 26DH4MQ assessed its drug-likeness, toxicity, enzyme inhibition, and ADME (Absorption, Distribution, Metabolism, and Excretion) parameters, highlighting its pharmaceutical potential. Furthermore, molecular docking and dynamics studies illustrated the compound's interaction with proteins, indicating its potential role as an insulin inhibitor.

H∞ optimum design and nonlinear seismic performance assessment of tuned-mass-damper-inerter (TMDI) supported by an auxiliary structure

Tuned Mass Damper Inerter (TMDI) and its simplified form, Tuned Inerter Damper (TID), are highly effective in mitigating seismic responses in buildings, particularly when rigidly connected to the ground. However, practical constraints often limit the feasibility of this ideal setup. This study introduces a novel configuration: the AS-type TMDI, which connects the TMDI to an auxiliary structure (AS) adjacent to the main building to simulate a ground connection. To design the AS-type TMDI, this research builds upon insights from studies on TMDIs in adjacent buildings and develops an analogous 3-DOF model representing the TMDI-linked adjacent-building system. This model incorporates two buildings of different heights, allowing the TMDI to be connected at any floor level. Utilizing fixed-point theory, the study derives an analytical solution for the optimal design of TMDI systems within this novel configuration. Additionally, a method is introduced to determine the optimal stiffness and design procedure for the AS itself. The performance of the proposed AS-type TMDI is evaluated through comprehensive nonlinear seismic analysis of a benchmark nine-story steel frame structure, accounting for material and geometric nonlinearities. Results demonstrate that the AS-type TMDI performs comparably to a virtually grounded TMDI in effectively reducing the seismic responses. Furthermore, this innovative configuration outperforms both a conventional retrofitting technique, where the building is rigidly connected to the AS, and a system where a viscous damper alone connects the main building to the AS. This highlights the AS-type TMDI's potential to significantly improve the building’s seismic performance.

Investigation on local mooring stresses of floating offshore wind turbines considering mooring chain geometrical and material nonlinearity

As the renewable energy industry moves towards deep water, mooring chains play an irreplaceable role in position keeping. The geometrical and material nonlinearity of the mooring chains significantly affects moored platform responses and mooring responses. To investigate local mooring stress evolution under wave loads, a simulation method was proposed, combining hydrodynamic loads derived from fully coupled simulations of floating offshore wind turbines (FOWTs). The simulation method, embedding the lumped mass mooring model, was validated by comparing the experimental data from OC4 semi-submersible wind turbines. Their reasonable segment numbers and the mooring structural damping ratio were also discussed. Based on the validated simulation technology, a coupled 3D-mooring analysis was performed, replacing linear mooring stiffness suggested in FAST tutorials with nonlinear mooring stiffness calculated by axial stretching the real-sized 3D chains. The nonlinear mooring stiffness is assumed, taking into account detailed geometry, nonlinear material properties, and contact behavior between chains. The nominal diameter of the real-sized 3D-chains was determined, so that the chains had the same volume per unit length as the validated case, ensuring a similar Morison's force on the mooring line. Then, the local mooring stresses were investigated by loading the derived nonlinear fairlead tension onto both sides of real-sized 3D chains in an explicit finite element software. The evolution of local mooring stresses under design wave loads with different wave headings of 0, 30, 60° was compared and discussed. As wave direction increases, this study indicated that the amplitude of local maximum principal stress decreases and its phase leads. Additionally, its magnitude is mainly influenced by axial tension force and contact behavior.

Stress-strain curve estimation from micropillar compression with transverse contraction effect

The Focused Ion Beam (FIB) technique and the associated compression testing capabilities provide versatile access to understanding the microstructural behaviour of materials. Among many objectives, determining the stress-strain relationship from experimental or numerical force-displacement data remains a fundamental challenge. However, for micropillers under compression, the inside deformation constraint is complex like in components and the transformation of a measured force-displacement curve into an accurate uniaxial stress-strain curve is not straightforward. In this context, in a previous numerical based analysis for perfect volume constancy or incompressibility the determination of reliable and accurate stress-strain curves from nonlinear load-deformation curves of micropillers was already verified. In the case of transverse contractions, however, numerical simulations of micropillers provide unexpected force-displacement behaviour, i.e. their force-displacement curves are almost superimposing and are very close to the force-displacements for incompressibility. This effect implies, that transverse contraction would have no contributions in micropillar compression. In contrast, independent simulations using a single finite element accurately explore the true uniaxial stress-strain behaviour for the whole range of transverse contractions. These are considered as the reference behaviour and are also treated by an analytical expression. With the presented new stress-strain estimation approach, including transverse contraction, any force-displacement curve from a micropillar under compression can be stepwise corrected. The first step of the new stress-strain curve estimation method, including transverse contraction, is carried out in the same way as in the preceding analysis for incompressibility, followed by further steps to obtain the final true stress-strain curve. Although the presented numerical analysis is exemplarily performed for the behaviour of fused silica, but the stress-strain approach is in the same manner generally applicable for a material behaviour with other stress-strain curves. The assumption behind is isotropic and nonlinear material behaviour.

The fractional solitary wave profiles and dynamical insights with chaos analysis and sensitivity demonstration

This work investigates the dynamics of solitary waves in a thin-film ferroelectric material model, an essential component of optical systems. The study recognizes the limitations of the inverse scattering transform in solving the Cauchy problem for this conformable thin-film ferroelectric material model and applies a new Kudryashov approach and Bernoulli’s equation technique to ordinary differential equations. We apply these methods to the present model and obtain closed form analytical solutions. A variety of traveling wave and soliton solutions are constructed, including kink, bell, bright, and dark soliton solutions. It is acknowledged that the nonlinear evolution equation can be transformed into an ordinary differential equation by applying traveling wave transformations. Suitable physical parameters are chosen to create 2D, 3D, and contour plots that graphically depict the graphical dispersion of obtained fractional soliton solutions. The impact of the conformable fractional parameter is further demonstrated by the graphical representation of solitons propagation. Furthermore, the study develops the Hamiltonian function of the dynamical system to discuss the system’s total energy in terms of momentum and position. While a chaos analysis describes chaotic, quasi-periodic, and periodic behaviors, a sensitivity analysis demonstrates how responsive the model is to various initial conditions. Due to their dual-purpose nature as nonlinear ferroelectric and dielectric materials, thin ferroelectric films are widely used in modern electrical devices.

Flexural behaviour and design of hybrid cold-formed steel built-up I-section beams

The current study investigates the flexural performance and design of hybrid cold-formed steel built-up I-section beams, which are increasingly popular in the construction industry. These beams combine the benefits of both an "I" section and a closed-box section in their cross-section profile. They are constructed from two identical plain channels placed back-to-back with space between them and top and bottom cover plates, fastened together by screws. A nonlinear finite element (FE) model was developed to consider initial geometric imperfections, material and geometric non-linearities. The model was validated against the test results of cold-formed steel (CFS) built-up beams from the companion paper and literature. Once validation was successful, a comprehensive parametric study using finite element modelling was conducted to generate data on hybrid cold-formed steel built-up I-section beams across a broader range of cross-sectional slenderness, hybrid ratio, aspect ratio of the cross section and thickness of the cover plates. The parametric results were used to analyse the influence of key parameters on the moment carrying capacity and buckling modes. The applicability of the current Direct Strength Method in the AISI S100–16 specifications was evaluated based on these results, revealing that it is unconservative. Additionally, modified design procedures and equations were suggested for hybrid CFS built-up I-section beams vulnerable to local buckling in major axis bending, which were then evaluated through reliability analysis.

An extended lumped damage mechanics IGABEM formulation for quasi-brittle material failure

This study proposes a new formulation for the mechanical modeling of quasi-brittle materials. The material degradation due to cracking is addressed through the Extended Lumped Damage Mechanics (XLDM) approach. The model is inserted into an IGABEM formulation, where Non-Uniform Rational B-Splines (NURBS) are the basis functions. A novel nonlinear solution technique has been developed for the numerical implementation. Crack propagation is captured using the initial stress field approach, widely utilized by the BEM community to account for nonlinear material behavior. The XLDM is coupled into an IGABEM formulation by discretizing part of the domain into cells, placed only where damage is expected to grow. Classical benchmark problems are presented to demonstrate the method’s capability and effectiveness. The results show excellent agreement with both experimental and numerical findings from the literature. Damage evolution is assessed through the band thickness opening, leading to material degradation. This method offers a new way of addressing damage mechanics problems within the BEM framework. It could benefit the BEM community, as traditional damage analysis within this numerical method often leads to significant time-consuming and elevated computational costs, which are mitigated by the formulation proposed herein.

An efficient method for evaluating the wind resistance performance of high-vertical standing seam metal cladding systems

Uplift wind-induced responses and failure criteria of high-vertical standing seam metal cladding systems (SSMCSs) are of paramount importance for evaluating their wind resistance performance. This paper proposes an efficient evaluation method that combines a highly efficient finite element (FE) model for structural response analysis with reasonable failure criteria, based on experimental and numerical investigation. The FE model incorporating the developed equivalent spring model is established with the calibrated stiffness from tensile tests and validated through the wind uplift resistance experiments conducted on large-scale prototype structures. The recorded structural responses from the experiments validate the feasibility of the FE model in simulating the geometric and material nonlinearities of the systems. To evaluate the wind resistance performance, the failure criteria are developed based on the observed pullout mechanisms and failure modes from the experiments. These criteria take the relative deformation of standing webs and the pullout resistance strength of seam connections as critical parameters, and the relationship between them is calibrated through a series of tensile tests using a self-designed fixture. Tensile test results show notable variability in the pullout resistance strength of seam connections, with a mean value decreasing as the relative rotational angle of the standing webs increases. According to the developed failure criteria, the ultimate uplift pressures evaluated from the FE analysis exhibit minimal positive deviations of 5.3 % and 7.3 % from the experimental results for different failure modes, respectively. This highlights the effectiveness of the proposed method in evaluating the wind resistance performance of high-vertical SSMCSs.

A statistical high-order reduced model for nonlinear random heterogeneous materials with three-scale micro-configurations

An effective statistical higher-order three-scale reduced homogenization (SHTRH) method is established to analyze the nonlinear random heterogeneous materials with multiple micro-configurations. Firstly, the various unit cell functions based on the microscale and mescoscale regions are given, and two expected homogenization coefficients are computed through Kolmogorov's strong laws of large number. Further, the nonlinear homogenized equations are formulated, and the corresponding reduced-order multiscale systems for displacement and stress solutions are derived by using the high-order unit cell solutions and homogenized solutions. The key features of the new statistical multiscale methods are (i) the novel reduced models established to solve the inelastic problems of random composites at a fraction of cost, (ii) the high-order homogenized solutions which do not need high-order continuity for the macro solutions of the random problems and (iii) the statistical high-order multiscale algorithms developed for analyzing the nonlinear random composites with three-scale structures. Finally, the effectiveness and correctness of the algorithm are confirmed according to several hyperelastic, plasticity and damage periodic/random composites with multiple-scale configurations. The computation shows that the proposed SHTRH methods are useful for analyzing the macroscopic nonlinear performance, and can efficiently catch the microscopic and mesoscopic information for the random heterogeneous composites.

Design of a monolithic silicon-on-insulator resonator spiking neuron

Increasingly, artificial intelligent systems look to neuromorphic photonics for its speed and its low loss, high bandwidth interconnects. Silicon photonics has shown promise to enable the creation of large scale neural networks. Here, we propose a monolithic silicon opto-electronic resonator spiking neuron. Existing designs of photonic spiking neurons have difficulty scaling due to their dependence on certain nonlinear effects, materials, and devices. The design discussed here uses optical feedback from the transmission of a continuously pumped microring PN modulator to achieve excitable dynamics. It is cascadable, capable of operating at GHz speeds, and compatible with wavelength-division multiplexing schemes for linear weighting. It is a Class 2 excitable device via a subcritical Hopf bifurcation constructed from devices commonly found in many silicon photonic chip foundries.

Effects of interfacial debonding on the stability of finitely strained periodic microstructured elastic composites.

Predicting failure initiation in nonlinear composite materials, often referred to as metamaterials, is a fundamental challenge in nonlinear solid mechanics. Microstructural failure mechanisms encompass fracture, decohesion, cavitation, compression-induced contact and instabilities, affecting their unconventional static and dynamic performances. To fully take advantage of these materials, especially in extreme applications, it is imperative to predict their nonlinear behaviour using reliable, accurate and computationally efficient numerical methodologies. This study presents an innovative nonlinear homogenization-based theoretical framework for characterizing the failure behaviour of periodic reinforced hyperelastic composites induced by reinforcement/matrix decohesion and interaction between contact mechanisms and microscopic instabilities. Debonding and unilateral contact between different phases are incorporated by employing an enhanced cohesive/contact model, which features a special nonlinear interface constitutive law and an accurate contact formulation within the context of finite strain continuum mechanics. The theoretical formulation is demonstrated using periodically layered composites subjected to macroscopic compressive loading conditions along the lamination direction. Numerical results illustrate the ways in which debonding phenomena, in conjunction with fibre microbuckling, may influence the critical loads of the examined composite solid. The sensitivity of the results obtained through the proposed contact-cohesive model at finite strain with respect to its implementation is also explored. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Prediction Accuracy of Hyperelastic Material Models for Rubber Bumper under Compressive Load.

Different hyperelastic material models (Mooney-Rivlin, Yeoh, Gent, Arruda-Boyce and Ogden) are able to estimate Treloar's test data series containing uniaxial and biaxial tension and pure shear stress-strain characteristics of rubber. If the rubber behaviour is only determined for the specific load of the product, which, in the case of rubber bumpers, is the compression, the time needed for the laboratory test can be significantly decreased. The stress-strain characteristics of the uniaxial compression test of rubber samples were used to fit hyperelastic material models. Laboratory and numerical tests of a rubber bumper with a given compound and complex geometry were used to determine the accuracy of the material models. Designing rubber products requires special consideration of the numerical discretization process due to the nonlinear behaviours (material nonlinearity, large deformation, connections, etc.). Modelling considerations were presented for the finite element analysis of the rubber bumper. The results showed that if only uniaxial compression test data are available for the curve fitting of the material model, the Yeoh model performs the best in predicting the rubber product material response under compressive load and complex strain state.