Composite Finite Element Analysis Research Articles

Simulation and experiment analysis of relationship between voids and permeability of composites

Due to the significant weight reduction advantage, aerospace composite tanks have become the focus of international competition of spacecraft. However, the permeation of small molecules at low temperature caused by the internal voids of composites is one of the key technical problems which restrict the engineering application of composite tanks. In this study, a combination of theoretical research and experimental research was adopted. By changing the curing pressures of the composites’ autoclave process, laminates with different porosities were prepared and tested for low-temperature permeability. Based on the grayscale processing and median filtering methods, a permeability prediction model with the true voids morphology of composite materials was established. Based on the random medium theory, the random voids model of composites was built to study the effect of void size and shape on the permeability of laminates. The results showed that the finite element analysis of composites, permeability based on the real voids morphology model was in good agreement with the experimental results, which proved the feasibility of this method. The permeation rate of laminates increased with the raised of porosity, and the internal porosity of the laminates could be diminished by improving the curing pressure so as to reduce the permeation of the composite components. Under the condition of a certain porosity, the laminates with small, stripe voids had a higher permeation rate than the laminates with large, circular voids.

New constitutive model for anisotropic hyperelastic biased woven fibre reinforced composite

This paper presents an improved constitutive model having application in finite element analysis of composites made of hyperelastic matrix with biased woven fabric reinforcement and is based on a pragmatic approach and the continuum mechanics theory. A generalised strain energy function is developed via a series of uniaxial tests in fibre warp and weft directions and via shear tests of representative samples of composite fabric. The proposed material characterisation approach is demonstrated on composites made of neoprene rubber matrix with nylon biased woven reinforcements having volume fraction composition 0·74 vol.-% neoprene and 0·26 vol.-% nylon. The material parameters in the anisotropic hyperelastic model are obtained by minimisation of least square residuals of uniaxial and pure shear energy densities against the respective strain invariants. Numerical simulations of uniaxial and bulge tests of the composites using the material model presented in this paper are shown to correspond well with results obtained from laboratory experiment.

Parameters Setting Impact Analysis of Composite Cockpit Finite Element Analysis Based on Properties of Composite Materials

At present, mechanics properties of composite at home and abroad only include data of the single-layer board. On the basis of researching literature of composite finite element analysis, approaches of setting composite three-dimensional parameters based on the parameters of single-layer material are summarized. By three-dimensional finite element analysis on composite whole cockpit, the impact of uncertain parameters on cockpit analysis results is studied. Adopting maximum stress criteria, maximum strain criteria and Tsai-Wu criteria to evaluate the initial failure of composite whole cockpit, the impact of material uncertain parameters on initial breaking strength prediction of cockpit is studied. The study can provide reference for three-dimensional finite element analysis of composite whole cockpit.

Stochastic problem of fiber‐reinforced composite with interface defects

The main purpose of the paper is to propose a new approach to stochastic computational modeling of interface defects in fiber‐reinforced composites. Interface defects with random radius and total number at the fiber‐matrix interface are modeled as an interphase between original composite components with the thickness obeying all the discontinuities and material parameters of this new, fictitious material are obtained by modified spatial averaging method. Such a model is used in the stochastic finite element analysis of composites in their original configuration. Next, the probabilistic moments of global effective properties of the entire composite are estimated, thanks to the traditional Monte Carlo simulation method implementation. Numerical experiments show that introduction of the interface defects results in significant increase of randomness level of the composite displacements and the homogenized elastic characteristics. Computer programs implemented can find their applications in digital image‐based analysis and the reliability analyses for fiber‐reinforced composites.

Three-dimensional finite element analysis of composites with coated spherical inclusions

A three-dimensional finite element analysis has been used to determine the internal stresses in a three-phase composite. The stresses have been determined for a variety of interphase properties, the thicknesses of the interphase and the volume fractions of particles. Young's modulus has been calculated from a knowledge of these stresses and the applied deformation. The calculations show that stress distributions in the matrix and the mechanical properties are sensitive to the interphase property in the three-phase composites. The interfacial stresses in the three-dimensional analysis are in agreement with results obtained by an axisymmetric analysis. The predicted bulk modulus in three-dimensional analysis agrees well with the theoretical solution obtained by Qui and Weng, but it presents a great divergence from that in axisymmetric analyses. An investigation indicates that this divergence may be caused by the difference in the unit cell structure between two models. A comparison of the numerically predicted bulk and shear modulus for two-phase composites with the theoretical results indicates that the three-dimensional analysis gives quite satisfactory results.

Integrated approach to finite element analysis of advanced composite structures

A new interactive and integrated approach to composite finite element analysis that addresses data management and graphical display issues is described. The entire abalysis cycle is considered, including the creation of ply properties from fibre and matrix properties, the definition of the laminate, the creation of the finite element model, the interrogation and sorting of the results, and the calculation of ply stresses, strains, and failure indices. New applications of interactive and graphical user interfaces and new approaches to managing both the finite element input and results data are also discussed. Included throughout are many examples using these new, integrated, composite finite element analysis techniques.