FATIGUE FAILURE OF FIBROUS COMPOSITE BASED ON MULTISCALE APPROACH

A framework was presented for a fatigue failure model of fibrous composites using a multiscale approach, which uses the fatigue data of the fiber and matrix materials, respectively. Using this model, fatigue failure of fibrous composite materials and structures can be predicted from the constituent material behaviors. To that end, fiber bundles were tested under cyclic loading to determine their residual strength and stiffness. A successful completion of the model is expected to replace many fatigue tests as the configuration of the fibrous composite is varied.

C2 weakens turn over frequency during melting of FexCy: insights from reactive MD simulations

The first-order phase transition plays a pivotal role in material behaviors, yet that of carbides, a type of important materials, has not been systematically studied. Herein, the melting process and...

Extreme-Modulation of Liquid Crystal Viscoelasticity via Altering Ester Bond Direction

The understanding of correlations between molecular-details and macroscopic material behaviors is a fundamental question of molecular chemistry/physics and offers practical interests in material design with fine-property-tunability. Herein, we demonstrate extreme...

Damage mechanisms of material in single-cone scratching

The scratching test has been a key method to characterize the basic mechanics of material in vast scenarios. Although attentions have been paid to this field for decades, a comprehensive analytical framework, which includes material flow, fracture initiation and crack propagation, is still missing. The wide application of scratching test and the accurate description of material behaviors in friction is thus limited. To address the problem, an analytical frame model was established in this study. The strain distribution and pileup ratio in the symmetry section of the front ridge was calculated. Furthermore, the ductile fracture law was also included to predict the mechanism and the initiation location of fracture in the scratching process. The predictive results were further validated by SEM observations of the scratched grooves. The effects of cone angle and material properties on the damage mechanisms of material in the scratching process were studied. It was revealed that the damage mechanism changes from shear failure to tensile failure, and further to plastic deformation with the increase of cone angle and the ratio of yielding stress to Young's modulus. Finally, a map of the damage mechanism of material in the scratching process was obtained by utilizing the developed model. The presented works are meaningful to the understanding of material behavior in ploughing, and helpful in predicting and controlling the surface quality of those parts subject to different machining and forming processes.

Ramberg–Osgood material behavior expression and large deflections of Euler beams

Several assumptions are commonly made throughout the literature with regard to the mechanical expression of material behavior under a Ramberg–Osgood material model; specifically, the negligible effects of nonlinearity on the elastic behavior of the material. These assumptions do not reflect the complicated nonlinearity implied by the Ramberg–Osgood expression, which can lead to significant differences in the member model response from the true material behavior curve. With the proposed approach, new explicit results for Ramberg–Osgood materials are achieved without relying on these assumptions of material and model expression. The only assumptions present within the proposed model are the standard mechanical assumptions of an Euler beam. A general nonlinear moment–curvature relationship for monotone material behaviors is constructed. Large deflections of cantilever Euler beams with rectangular cross-sections under a combined loading are modeled. Numerical validation of this new method against results already given in the literature for the special cases of linear and power-law material behaviors are provided. An analysis is presented for three common material behavior relationships, with a focus on how these relationships are expressed through the deflection of members under the application of force within the model; this analysis clearly demonstrates that the sub-yield nonlinear behavior of the Ramberg–Osgood expression can be significant. The distinctions between material behavior expression demonstrated in this analysis have been long overlooked within the literature. This work addresses a gap between the modeling of Ramberg–Osgood material behaviors and the implementation of that model in mechanics.

A failure criterion revision method for composite materials

Failure criterion predictions often have substantial errors due to the complexity of failure mechanism or different material behaviors, especially composite failure. In this study, an example of delamination is employed to demonstrate the general failure criterion revision of composites. In the present research, the failure function can be raised to a higher order, and also be reduced to a lower one, by fitting the exponents of failure criterion. This method can be easily used to describe the observed, experimented, or computed data, particularly with no law or no rules. Further, the importance of this exponent revision is amplified when the failure surface becomes more complicated. The proposed approach is also to define and calculate the failure criteria of multiplying laminates.