The anisotropic mechanical properties of a Ti alloy composite reinforced with SiC fibers have been investigated and rationalized using analytical models. The appropriate material model for this composite involves the following features: an interface that debonds and slides, a flaw insensitive ductile matrix, and high-strength elastic fibers subject to residual compressive stress caused by thermal expansion mismatch. This, model is broadly consistent with the longitudinal, transverse, and shear properties of the composite.

The anisotropic mechanical properties of a Ti matrix composite reinforced with SiC fibers

This paper describes the concept of a lightweight and deformable structure with intrinsic distributed electromechanical actuation, potentially suitable to develop soft linear peristaltic pumps for incompressible fluids The proposed system is represented by a series of radially expanding flexible tubular modules, made of dielectric elastomers (DEs), as one of the most promising classes of electroactive polymers for actuation Each module consists of a cylindrical hollow DE actuator, working in purely radial mode with specific boundary constraints The static electromechanical transduction performance of such a module was investigated analytically, numerically, and experimentally For this purpose, predictions obtained from an analytical model, derived in the hypothesis of linear elasticity, were compared with those provided by a finite-element method Both models were validated by means of a comparison with experimental data, obtained from a silicone-made prototype module Results permitted to obtain a simple tool of simulation, suitable to predict the performance of the system in terms of both displaced volume and driving pressure, as a function of the material elastic modulus and the applied voltage

Electroactive Elastomeric Actuator for All-Polymer Linear Peristaltic Pumps

This paper presents the results of a study of the effect of interface microstructure and related mechanical properties on the overall mechanical behaviour of an Al alloy metal matrix composite (A356) containing 10 vol.-%SiC particles. Two different interface microstructures were obtained by using as received or oxidised SiC particles. For the oxidised particle composites, TEM observations show a spinel phase (MgAl2O4) formation at the Al/SiC interface, whereas for as received particle composites very few chemical reactions are observed. The particle oxidation reduces the mechanical strength (0·2% proof stress (σ0·2 and ultimate tensile strength (UIS)) and increases ductility ɛf considerably. In addition, it is evident from tensile tests carried out in an SEM that these two different types of overall behaviour are a result of different failure processes: particle rupture in the as received particle composites and interface decohesions in the oxidised particle composites.MST/1105

Effect of interfacial oxide layer in Al–SiC particle composites on bond strength and mechanical behaviour

Modeling of imperfect bonding in fiber reinforced brittle matrix composites

The influence of moisture content (MC) on the tension-compression (Te-Co) asymmetry of beech wood has been examined. The elastic and strength parameters, including Te and Co Young’s moduli, Poisson’s ratios, and ultimate and yield stress values, were determined and compared in terms of different MCs for all orthotropic directions. The results reveal a distinctive Te-Co strength asymmetry with a moisture dependency that is visualized clearly by the Te to Co yield stress ratio. The Te-Co asymmetry is further shown by the inequality of the elastic properties, known as the “bimodular behavior”. The latter is proven for the Young’s moduli values in the radial and tangential directions and for individual Poisson’s ratios. Although the bimodularity of the Young’s moduli is significant at low MC levels, there is no evidence of moisture dependency on the Te-Co asymmetry of the Poisson’s ratios.

/pdf/moisture-dependent-orthotropic-tension-compression-asymmetry-dofnhc5qky.pdf

Moisture-dependent orthotropic tension-compression asymmetry of wood

A mathematical model is developed to predict the transverse elastic moduli of unidirectional fiber composites. Two cases of fiber/matrix interfacial bondings are investigated: perfect bonding and complete debonding,i.e., no transferring of tensile stress on surfaces where the fiber and matrix materials are separated. Fibers are assumed to exhibit transverse isotropy, and the elastic interactions among fibers are also considered. In the analysis of the completely debonded case, the cavity formation model is adopted and the original fiber and surrounding cavities are replaced by an imaginary anisotropic inclusion. Closed form solutions of effective elastic moduli are obtained for transverse tensile and compressive moduli, and transverse shear moduli. The limiting case of fiber-like voids is also studied. Numerical results are presented for two metal matrix composites, where the optimal wetting between the fiber and matrix is difficult to be obtained and hence the interfacial bonding and transverse property have been major concerns.

K. Takahashi

Papers

Transverse elastic moduli of unidirectional fiber composites with interfacial debonding