Three-dimensional Five-directional Braided Composites Research Articles

Shape memory behaviors of three-dimensional five-directional braided composites with different axial yarns arrangements

The effect of braided structure on shape memory behaviors of 3D braided composites is critical to design the responses of the composite under external fields. Here we report the effect of axial yarn on shape memory behaviors of three-dimensional five-directional (3D5d) braided shape memory polymer composites (SMPCs) under bending. It was found that the axial yarns will improve bending stiffness and electro-thermal behaviors significantly. The thermomechanical deformation and shape memory effect of SMPCs are influenced by the braiding structural parameters. Specifically, the 3D5d SMPCs exhibits a 53.6% increase in bending recovery force and a faster shape recovery speed than those of 3D four-directional SMPCs. We found from finite element analyses (FEA) that the axial yarns positions influence the inner stress distribution and shape memory behaviors of SMPCs. The axial yarns distributed on both sides of SMPC influence the shape memory behaviors more than those of the middle layer.

Experimental investigation on compressive properties of three-dimensional five-directional braided composites in hygrothermal environment

Abstract This article describes work concerning the compressive properties in hygrothermal environment of three-dimensional (3D) five-directional braided composites. Hygrothermal aging tests at temperatures of 40, 60, and 80°C and compression tests were carried out on the specimens with three braiding angles of 15, 25, and 35°. The surface morphologies of the samples taken using scanning electron microscope before and after the hygrothermal aging test were used to analyze the influence of the hygrothermal environment on the internal structure of braided composites. The experimental results indicate that the hygrothermal environment has a more influence on the specimens with a braiding angle of 15°, and the greater the moisture absorption percentage, the lower the retention ratios of compressive strength and modulus. Compared with room temperature, the compressive strength and modulus of specimens with a braiding angle of 15° reduced by 72.2 and 82.7% as the water bath temperature increased from 40 to 80°C. Moreover, the failure mechanisms of 3D five-directional braided composites in the hygrothermal environment were analyzed.

Refine reconstruction and verification of meso-scale modeling of three-dimensional five-directional braided composites from X-ray computed tomography data

This paper proposes a statistical approach to generate the refine meso-scale representative volume element of three-dimensional (3D) five-directional braided composites considering the fabric compaction and the axial yarn torsion. The method firstly extracts the regions of interest to obtain the reference model (R-model) from the X-ray computed tomography (Micro-CT) data. Then, the geometric parameters of the collected yarns of R-model are statistically analyzed based on the scanning tomograms. Consequently, the meso-scale statistical model (S-model) are reconstructed after being fitted with the appropriate function. Moreover, for the validation of S-model, the traditional ideal model (I-model) and the experimental tests are considered. The results show that the proposed S-model is capable of accurately presenting the effects of the fabric compaction and yarn torsion on the mechanical behaviors of 3D braided composites, validated by the elastic constants and the damaged modes.

High temperature compressive behavior of three-dimensional five-directional braided composites

Abstract An experimental study was performed to investigate the high temperature compressive properties and failure mechanism of three-dimensional (3D) five-directional braided composites. The compression tests of 3D braided composites were conducted at six different temperatures. The failure modes, stress-strain curves, compressive modulus and strength at high temperature were analyzed and compared with those at room temperature. The results showed that temperature has a visible impact on these parameters. The 3D braided composites failed due to shear fracture, and the stress-strain curves exhibited obvious linear elasticity and a brittle failure feature at 20 and 50 °C, while the failure was characterized by fiber/matrix interface debonding, fiber bundles loosening and by outward expansion, and the stress-strain curves exhibited an obvious non-linear trend and a plastic failure feature at 70, 90, 110 and 130 °C. The compressive modulus and strength decreased as temperature increased. The compressive modulus and strength decreased by 92.9 % and 94.1 % as the temperature increased from 20 °C to 130 °C, which was mainly due to the degradation of the matrix properties and fiber/matrix interface properties at high temperature.

Meso-scale progressive damage of 3D five-directional braided composites under transverse compression

A study is conducted with the aim of evaluating the transverse compressive behaviors of three-dimensional five-directional braided composites based on the meso-scale representative volume cells. Finite element models with three kinds of interior braiding angles, 20°, 30°, and 45°, are established on the basis of the realistic cross-section shape of each yarn. A damage mechanics model, which is implemented by user-defined material subroutines in ABAQUS/Standard, is used to investigate the mechanical responses and the damage initiation/evolution throughout the transverse compression. For the verification of numerical results, a series of transverse compression tests are conducted. Numerical results indicate that the transverse compression strength of three-dimensional five-directional braiding composite is strongly dependent on the matrix properties, and is not very sensitive to the braiding angle. The predicted results show good agreement with the relevant experimental data, demonstrating the applicability of meso-scale finite element model.

Meso-scale finite element analyses of three-dimensional five-directional braided composites subjected to uniaxial and biaxial loading

A meso-scale finite element-based model has been developed to evaluate the uniaxial and biaxial strength characterizations of three-dimensional five-directional braided composites. The representative volume cells are established based on the realistic geometry cross sections. A continuum damage mechanics model, which is implemented as a user-defined material subroutine in the ABAQUS commercial finite element code, is introduced to predict the mechanical responses and the failure locus under uniaxial and biaxial loadings. For the verification of numerical results, a series of tensile and compressive tests are conducted along the longitudinal and transverse directions. The results show that under uniaxial loading, the calculated max stress and the final damage morphology agree well with the experimental data. Moreover, it is found that the interaction effect between the axial stress and the shear stress is not apparent, whereas that between two axial stresses becomes significant. It is expected that such a numerical investigation will provide useful information for building a strength criterion of three-dimensional five-directional braided composites.

Transverse tensile damage behaviors of three-dimensional five-directional braided composites by meso-scale finite element approach

In this paper, the meso-scale finite element method is used to evaluate the transverse tensile damage behaviors of three-dimensional five-directional braided composites based on the representative volume cell. Finite element models with two kinds of interior braiding angles, 30° and 45°, are established on the basis of the realistic geometry shape of each yarn. A continuum damage mechanics model, which is implemented as a user-defined material subroutines in the ABAQUS commercial finite element code, is used to capture the complete damage initiation/evolution in yarns and matrix. The local responses and the failure mechanisms are analyzed. Numerical results show that the transverse tensile strength and the failure mechanisms are significantly influenced by the braiding angle. The predicted stress–strain responses and final damage morphology agree well with the experimental data, verifying the applicability of the meso-scale finite element method.

Microstructure and mechanical properties of three-dimensional five-directional braided composites

Three-dimensional (3D) five-directional braided composites are significant structural materials in the fields of astronauts and aeronautics. On the basis of the 3D five-directional braiding process, three types of microstructural unit cell models are established with respect to the interior, surface and corner regions. The mathematical relationships among the structural parameters, such as fiber orientation, fiber volume fraction, the yarn packing factor, are derived. By using these three unit cell models, a micromechanical prediction procedure is described to simulate the stiffness and strength properties of 3D five-directional braided composites. Only the in situ constituent fiber and matrix properties of the composites and the fiber volume proportion are required in the simulation. The stress states generated in the constituent fiber and matrix materials are explicitly correlated with the overall applied load on the composites. The predictive stiffness and strength are in good agreement with available experimental data, which demonstrates the applicability of the present analytical model.