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"Fiber reinforced materials"
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High-temperature mechanical hysteresis in ceramic-matrix composites
\"This book focuses on mechanical hysteresis behavior in different fiber-reinforced ceramic-matrix composites (CMCs), including 1D minicomposites, 1D unidirectional, 2D cross-ply, 2D plain-woven, 2.5D woven, and 3D needle-punched composites. Ceramic-matrix composites (CMCs) are considered to be the lightweight high-temperature materials for hot-section components in aeroengines with the most potential. To improve the reliability and safety of CMC components during operation, it is necessary to conduct damage and failure mechanism analysis, and to develop models to predict this damage as well as fracture over lifetime - mechanical hysteresis is a key damage behavior in fiber-reinforced CMCs. The appearance of hysteresis is due to a composite's internal damage mechanisms and modes, such as, matrix cracking, interface debonding, and fiber failure. Micromechanical damage models and constitutive models are developed to predict mechanical hysteresis in different CMCs. Effects of a composite's constituent properties, stress level, and the damage states of the mechanical hysteresis behavior of CMCs are also discussed. This book also covers damage mechanisms, damage models and micromechanical constitutive models for the mechanical hysteresis of CMCs. This book will be a great resource for students, scholars, material scientists and engineering designers who would like to understand and master the mechanical hysteresis behavior of fiber-reinforced CMCs\"-- Provided by publisher.
BOOK
On the quasi-incompressible finite element analysis of anisotropic hyperelastic materials
Quasi-incompressible behavior is a desired feature in several constitutive models within the finite elasticity of solids, such as rubber-like materials and some fiber-reinforced soft biological tissues. The
Q1P0
finite element formulation, derived from the three-field Hu–Washizu variational principle, has hitherto been exploited along with the augmented Lagrangian method to enforce incompressibility. This formulation typically uses the unimodular deformation gradient. However, contributions by Sansour (Eur J Mech A Solids 27:28–39,
2007
) and Helfenstein et al. (Int J Solids Struct 47:2056–2061,
2010
) conspicuously demonstrate an alternative concept for analyzing fiber reinforced solids, namely the use of the (unsplit) deformation gradient for the anisotropic contribution, and these authors elaborate on their proposals with analytical evidence. The present study handles the alternative concept from a purely numerical point of view, and addresses systematic comparisons with respect to the classical treatment of the
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element and its coalescence with the augmented Lagrangian method by means of representative numerical examples. The results corroborate the new concept, show its numerical efficiency and reveal a direct physical interpretation of the fiber stretches.
Journal Article
Convexity and Quasiconvexity in a Cosserat Model for Fiber-Reinforced Elastic Solids
An inequality of the quasiconvexity type is derived in the context of a Cosserat model for fiber-reinforced elastic solids in which the Cosserat rotation field accounts for the kinematics of the embedded fibers, modeled as extensible, unshearable spatial rods. This is shown to be equivalent to the requirement that the fiber bend-twist strain vector associated with an energy minimizer be a point of convexity of the operative strain-energy function. The analysis requires careful consideration of constraints associated with the fact that fibers are convected by the continuum deformation field as material curves.
Journal Article
Topology optimization considering Tsai–Wu yield criterion for composite materials
The increasing popularity of composites reinforced with fiber has spurred the development of sophisticated additive manufacturing technologies, allowing for precise tailoring of fiber orientation for optimization purposes. Despite significant advancements in fiber orientation optimization, the key challenge posed by stress yield criteria still needs to be solved. This work presents a novel optimization approach, aiming to minimize structural volume while incorporating local stress constraints based on the Tsai–Wu criterion. The proposed NDFO-adapt method optimizes material distribution, fiber angles, and the penalization field. This optimization process involves multiple design variables, and new schemes are introduced to determine these variables using an optimization algorithm and adaptive continuations based on the structural grayscale. Numerical examples show the effectiveness of the proposed method, providing valuable insights for optimizing fiber-reinforced materials considering stress constraints with potential applications in the design of lightweight, high-strength structures.
Journal Article
Finite Bending of Fiber-Reinforced Visco-Hyperelastic Material: Analytical Approach and FEM
This paper presents a new anisotropic visco-hyperelastic constitutive model for finite bending of an incompressible rectangular elastomeric material. The proposed approach is based on the Mooney–Rivlin anisotropic strain energy function and non-linear visco-hyperelastic method. In this study, we aim to examine the mechanical response of a reinforced viscoelastic rectangular bar with a group of fibers under bending. Anisotropic materials are typically composed of one (or more) family of reinforcing fibers embedded within a soft matrix material. This operation may lead to an enhancement in the strength and stiffness of soft materials. In addition, a finite element simulation is carried out to validate the accuracy of the analytical solution. In this research, the well-known stress relaxation test, as well as the multi-step relaxation test, are examined both analytically and numerically. The results obtained from the analytical solution are found to be in good agreement with those from the finite element method. Therefore, it can be deduced that the proposed model is competent in describing the mechanical behavior of fiber-reinforced materials when subjected to finite bending deformations.
Journal Article
Effects of Microstructures, Heterogeneity, and Imperfectness on Propagation of SH-Waves in a Fiber-Reinforced Layer Sandwiched Between Two Microstructural Half-Spaces
The objective of the paper is to investigate the propagation behavior of horizontally polarized shear waves (SH-waves) in an inhomogeneous fiber-reinforced layer which is sandwiched between two microstructural half-spaces. The half-spaces are modeled using size-dependent consistent couple stress theory. The mathematical formulations of consistent couple stress theory contains a length scale parameter called characteristic length. Characteristic length is comparable with the size of internal microstructure of the material and introduces the role of size dependency into the problem. The propagation behavior of SH-waves is investigated in an inhomogeneous fiber-reinforced layer under two different scenarios, first when the layer is perfectly attached to the half-spaces and second when the layer is in imperfect contact with the half-spaces. Dispersion and damping relations are calculated for the propagation of SH-waves in both cases separately using suitable boundary conditions. Some special cases are also generated under different conditions. The impact of various parameters such as characteristic length, inhomogeneity, reinforcement, and imperfectness are manifested graphically on the phase and damping velocities of the SH-waves.
Journal Article
Bulging initiation and propagation in fiber-reinforced swellable Mooney–Rivlin membranes
This article considers a thin-walled hollow cylinder, which is composed of a fibrous and swellable hyperelastic material. The fibers are arranged in two families and they are taken to be parallel within each fiber family. The two fiber families are also assumed to be mechanically equivalent and symmetrically disposed in the ground substance material. At each instant of the homogeneous swelling, the material is taken to be incompressible. This article studies the interplay of swelling, fiber orientation, and the mechanical properties of the constituents on the initiation as well as on the axial propagation of bulging.
Journal Article
Effect of mullite on the friction stability of carbon fiber-reinforced friction material
Purpose
The purpose of this paper is to investigate the effect of mullite on the mechanical properties and friction of carbon fiber (CF)-reinforced friction material.
Design/methodology/approach
CF-reinforced friction materials with varying content of mullite were fabricated by hot press molding, and then the tribological properties were tested on the MRH-3-type tribometer under ambient conditions with the ring-on-block configuration.
Findings
The experimental results indicated that the addition of mullite increased the density and compressive strength of friction material. However, the flexural strength of friction material decreased by 16% with the addition of 15 Wt.% mullite. The friction coefficient was proportional to the mullite content. Friction material with 12.5 Wt.% mullite showed the highest friction stability under different loads, whereas friction material with 10 Wt.% mullite exhibited the highest friction stability under different sliding speeds.
Originality/value
By boosting the resistance to deformation under load and increasing the specific heat capacity, mullite contributed significantly to the friction stability of the friction material.
Journal Article
Characterization of the Mechanical Properties of Fiber-Reinforced Modified High Water Content Materials
This research examines the mechanical properties of fiber-reinforced modified high-water content materials intended for mining backfill applications. Conventional high-water content materials encounter several challenges, including brittleness, inadequate crack resistance, and insufficient later-stage strength. Basalt fiber (BF) and polypropylene fiber (PP) were integrated into the material system to establish a reinforcing network through interfacial bonding and bridging mechanisms to mitigate these issues. A total of nine specimen groups were developed to assess the influence of fiber type (BF/PP), fiber content (ranging from 0.5% to 2.0%), and water cement ratio (from 1.25 to 1.75) on compressive, tensile, and shear strengths. The findings indicated that basalt fiber exhibited superior performance compared to polypropylene fiber, with a 1% BF admixture yielding the highest compressive strength of 5.08 MPa and notable tensile enhancement attributed to effective pore-filling and three-dimensional reinforcement. Conversely, higher ratios (e.g., 1.75) resulted in diminished strength due to increased porosity, while a ratio of 1.25 effectively balanced matrix integrity and fiber reinforcement. Improvements in shear strength were less significant, as excessive fiber content disrupted interfacial friction, leading to a propensity for brittle failure. In conclusion, basalt fiber-modified high water content materials (with a 1% admixture and a ratio of 1.25) demonstrate enhanced ductility and mechanical performance, rendering them suitable for mining backfill applications. Future investigations should focus on optimizing the fiber matrix interface, exploring hybrid fiber systems, and conducting field-scale validations to promote sustainable mining practices.
Journal Article
Foundation of Polar Linear Elasticity for Fibre-Reinforced Materials
This study is motivated by evidence suggesting that the equations of polar elasticity of fibre-reinforced materials are non-elliptic even within the regime of infinitesimal deformations. In its endeavour to resolve this issue, which in symmetric-stress elasticity emerges in the regime of finite deformations only, it lays the foundation for development of a second-gradient theory of linear elasticity. Complete formulation of this new theory is achieved for locally transverse isotropic materials; namely, materials having embedded a single unidirectional family of arbitrarily shaped fibres which are resistant in bending, stretching and twist. The associated analysis shows that, indeed, the obtained Navier-type displacement equations are not elliptic. They accordingly predict that there exist in the material weak discontinuity surfaces, which may indeed be activated within the infinitesimal deformation regime. Surfaces containing the fibres are certainly such surfaces of weak discontinuity; this result may be not irrelevant to numerous practical situations where straight metallic fibres in fibre-reinforced concrete structures emerge partially de-bonded and exposed from their concrete matrix. Nevertheless, the analysis reveals further that additional surfaces of weak discontinuity may well exist in the locally transverse isotropic material of interest. An extension framework is also outlined towards cases of fibrous composites containing two or more families of non-perfectly flexible fibres.
Journal Article