Prediction of elastic modulus and mid-span deflection of bamboo-wood composite laminates

To better guide the manufacturing of bamboo-wood composite laminates, classical theory, first-order shear theory, and finite element method were used to predict the elastic modulus and deflection of bamboo-wood composite laminates. The influence of the adhesive layer on the elastic modulus and deflection of composite materials was considered. The effect of transverse shear on the mechanical properties of materials became smaller and smaller with an increasing span-to-height ratio. The effects of the adhesive layer on the elastic modulus and deflection were ± 0.5% and -0.1% to 0.3%, respectively. The transverse elastic modulus and mid-span deflection predicted by the three methods were quite different from the experimental results. When the span-to-height ratio was equal to 20, the prediction error of longitudinal elastic modulus by the three methods was less than 6%, which can be used to predict the elastic modulus of composite materials. The results provide a novel method to predict the properties of bamboo-wood composite laminates.

Transient dynamic response of a nanocomposite conical shell with a ring stiff-ener under the action of an impact load

This work is devoted to the study of transient processes occurring in a nanocomposite shell with a ring stiffener under the action of an impact load. Nanocomposites are promising new materials for the aerospace industry. However, the analysis of dynamic processes in nanocomposite structures requires the development of new methods due to the anisotropic, functional-gradient nature of these materials. The problem is further complicated if a composed structure is to be analyzed. This paper proposes a model of deformation of a functionally graded composite conical shell reinforced with carbon nanotubes with an isotropic ring stiffener. The deformation of the functionally graded nanocomposite conical shell is described by Reddy’s high-order shear theory, and the deformation of the ring stiffener is described by the Euler–Bernoulli hypotheses. The Rayleigh–Ritz method is used to study the natural vibrations of the composite structure. The main variables are the displacements and angles of rotation of the conical shell. A mathematical model of the transient response of the structure under the action of an impact load is obtained in the form of a linear dynamic system in generalized coordinates. To obtain this system, the prescribed form method is used. Numerical studies of the free dynamics and transient response of a nanocomposite conical shell with an isotropic ring stiffener of rectangular section under the action of an impact load were carried out. The results of the numerical modeling of the transient process in the shell showed a close agreement with the results of finite element modeling in the ANSYS package. The effect of the ring stiffener on the amplitudes of the transient response of the nanocomposite shell is investigated. It is shown that the ring-stiffener significantly reduces the amplitude of the transient response of the composite conical shell when it is subjected to an impact load. The proposed method and the conclusions drawn may be used in the aerospace industry in the design of nanocomposite units for multistage launch vehicles.

Research of Fracture Mechanics Applied in the Cutting Process of Plastic Metals

Shear theory is the mainstream view to explain the cutting process. Because of the complexity of the cutting process, it is still difficult to explain and predict the physical phenomena in the cutting process accurately by shear theory. While some physical phenomena can be well explained by fracture theory. At the same time, with the development of fracture theory, fracture phenomenon in cutting process has attracted scholarsattention again. Therefore, the early development and current application of fracture theory in the study of cutting process are reviewed in detail. The research results and key points of fracture theory in cutting process are summarized. The development direction of fracture theory in the cutting process is briefly discussed. It is considered that the integration of fracture theory and shear theory is an effective way to study cutting mechanism, and the cutting process is divided into six stages in order to integrate fracture and shear theory.

A parameter-free double-shear theory for lath martensite

A double-shear theory is introduced that predicts the commonly observed {5 5 7}γ habit planes in low-carbon steels. The novelty of this theory is that the shearing systems are chosen in analogy to the original (single-shear) phenomenological theory of martensite crystallography as those that are macroscopically equivalent to twinning. Out of all the resulting double-shear theories, the ones leading to certain {h h k}γ habit planes naturally arise as those having small shape strain magnitude and satisfying a condition of maximal compatibility, thus making any parameter fitting unnecessary. An interesting finding is that the precise coordinates of the predicted {h h k}γ habit planes depend sensitively on the lattice parameters of the face-centered cubic (f.c.c.) and body-centered cubic (b.c.c.) phases. Nonetheless, for various realistic lattice parameters in low-carbon steels, the predicted habit planes are near {5 5 7}γ. The examples of Fe–0.252C and Fe–0.6C are analyzed in detail along with the resulting orientation relationships which are consistently close to the Kurdjumov–Sachs model. Furthermore, a MATLAB app `Lath Martensite' is provided which allows the application of this model to any other material undergoing an f.c.c. to b.c.c. transformation.

Analysis of Bending of Ceramic-Metal Functionally Graded Plates with Porosities Using of High Order Shear Theory

This work consists of the analysis of the bending responses of porous Ceramic-Metal functionally graded (FG) rectangular plates are investigated according to high order shear deformation theory. The proposed theory contains four unknowns unlike the other theories which contains five unknowns, but it checks the boundary conditions without constraints on the upper and lower plate surfaces. Both the effect of shear strain and normal deformation are included in the present theory and so it does not need any shear correction factor. The equilibrium equations according to the porous FG plates Ceramic-Metal are derived. The solution of the problem is derived by using Navier’s technique. Numerical results have been reported, and compared with those available in the open literature for non-porous plates. Effects of the exponent graded and porosity factors are investigated.