Table 1 - uploaded by R. Rolfes
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![Fig. 1. Fibre and inter-fibre failure modes (Puck [17])](profile/R-Rolfes/publication/228337082/figure/fig9/AS:668417807900678@1536374632256/Fibre-and-inter-fibre-failure-modes-Puck-17_Q320.jpg)
Industrialised infusion processes enable a cost-effective possibility to produce textile composite structures compared to pre-impregnated composite systems (Prepregs). Particularly with regards to high performance structures one has to be familiar with the material behaviour and the failure characteristic to apply fibre reinforced composites profit...
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Citations
... The potential of this method for micro-scale unit cells of textile composites for finite element analysis has been shown by Swan et al. [84]. Rolfes et al. [77] and Ernst et al. [19] use the voxel mesh in damage mechanics of unit cells within the scope of multi-scale consideration. And Mishnaevsky [68] proposes an automated voxel mesh generation procedure to analyse composite structures on micro-scale. ...
Fibre reinforced plastics are widely used for energy dissipating parts. Due to their superior strength to density ratio they provide a high performance and are ideal for lightweight design for crashworthiness. For this, it is essential that the mechanical behaviour of fibre reinforced composites can be predicted correctly
by simulation. However, due to the complex inner structure, this is still a challenging task, in particular in case of highly nonlinear crash loading. In this work, a new purely virtual method is developed, which derives the complex fibre structure of a filament wound tube by a chain of numerical simulations. Thereby a finite element simulation of the fibre placement, taking into account the occurring physical effects, constitutes the fundamental base. Based on the results of the manufacturing simulation, a 3D fibre architecture is generated
and compared to the real existing structure. The fibre structure, combined with an automatic matrix implementation algorithm, subsequently provides a finite element model of the composite on meso-scale. Using micro-scale analysis, effective material properties for the roving structure, based on filament-matrix interaction, are derived. Incorporation of the effective properties in a USER MATERIAL model completes the finite element model generation. The mesoscale model is subsequently used to analyse the filament wound tube in terms of quasi-static and crash loading. Finally, the obtained results are compared to experimental observations.
... Due to their great potential for weight savings, textile composites are becoming increasingly important in many fields of application, such as wind turbine rotor blades, transportation, sporting, construction and medical applications. Textile composites offer several advantages compared to unidirectional (UD) composites, such as lower production costs, better drapability, higher delamination and impact strength, see [1]. However, their mechanical inplane properties, stiffness as well as strength, are lower than those of UD-composites. ...
In this paper, a novel orthotropic layer based failure criterion for modelling progressive failure of non-crimp fabrics is presented. The strength parameters and stiffnesses needed for this failure criterion are obtained from virtual material tests. Therefore, a finite element multiscale algorithm is used to model the effect of lower scale inhomogeneities on macroscale material behavior. With this multiscale approach it is possible to make predictions for one single layer within a textile preform solely from the knowledge of the mechanical behavior of the constituents fiber and matrix and from the textile fiber architecture. The obtained stiffnesses and strengthes for one textile layer are used as input data for the novel orthotropic failure criterion presented in this paper. In order to show the workability of this failure criterion, finite element simulations of coupon tests and of a three-point bending test of a textile composite are shown and compared to experimental data.
Owing to the importance of fibre architectures in the design of textile composite materials, understanding their effect on the failure mechanisms of these composites have taken more considerations. In this regards, non-crimp preform and 2/2 twill fabric have been manufactured from glass fibre by using pin-board and power loom machines respectively, and subsequently composites laminates from both preforms are manufactured via vacuum assisted resin infusion method. In addition, quasi-static tensile and compressive strength tests have been conducted for the composite laminates that have same volume fraction. Damage failure mechanisms that occurred in compressive strength in both composites have been examined by using scanning electronic machine (SEM). Findings show that the mechanical properties are primly determined by fibre architectures and the presence of fibre crimp can further weaken tensile and compressive strength values. It was noticed that the tensile strength of non-crimp composite was 610 MPa whereas that of twill fabrics composite laminates it was found to be 350 MPa and 440 MPa in warp and weft directions respectively. Moreover, in case of twill fabric composites, fibre crimp has a considerable effect on the mode and characteristics of damage in the compressive loading; this leads to fibre fracture and kinks that primarily happened in the intersection point of warp and weft yarns. Results also showed improved ductility, strain to failure and absorbing energy in the twill fabric composites compared to non-crimp composites under in-plane shear strength test.
The complex three-dimensional structure of textile composites makes the experimental determination of the material parameters very difficult. Not only the number of constants increases, but especially through-thickness parameters are hardly quantifiable. Therefore an information-passing multiscale approach for computation of textile composites is presented as an enhancement of tests, but also as an alternative to tests. The multiscale approach consists of three scales and includes unit cells on micro- and mesoscale. With the micromechanical unit cell stiffnesses and strengths of unidirectional fiber bundle material can be determined. The mesomechanical unit cell describes the fiber architecture of the textile composite and provides stiffnesses and strengths for computations on macroscale. By comparison of test data and results of numerical analysis the numerical models are validated.
To consider the special characteristics of epoxy resin and fiber bundles two material models are developed. Both materials exhibit load dependent yield behavior, especially under shear considerable plastic deformations occur. This non-linear hardening is considered via tabulated input, i.e. experimental test data is used directly without time consuming parameter identification. A quadratic criterion is used to detect damage initiation based on stresses. Thereafter softening is computed with a strain energy release rate formulation. To alleviate mesh-dependency this formulation is combined with the voxel-meshing approach.
Epoxy resin is modeled with the first, isotropic elastoplastic material model regarding a pressure dependency in the yield locus. As the assumption of constant volume under plastic flow does not hold for epoxy resin, a special plastic potential is chosen to account for volumetric plastic straining.
To describe the material behavior of the fiber bundles, the second, transversely isotropic, elastoplastic material model is developed. The constitutive equations for the description of anisotropy are formulated in the format of isotropic tensor functions by means of structural tensors. Opposed to the isotropic case the hardening curves are not obtained by experiment but by simulations performed done with the micromechanical model. So the hardening and softening curves from the micro model simulation, reflecting the homogenized material parameters from the micro model, are submitted to the next scale, the mesomechanical model.
The experimental determination of stiffness and strength of textile composites is expensive and time-consuming. Experimental tests are only capable of delivering properties of a whole textile layer, because a decomposition is not possible. However, a textile layer, consisting of several fiber directions, has the drawback that it is likely to exhibit anisotropic material behavior. In the presented paper a finite element multiscale analysis is proposed that is able to predict material behavior of textile composites via virtual tests, solely from the (nonlinear) material behavior of epoxy resin and glass fibers, as well as the textile fiber architecture. With these virtual tests it is possible to make predictions for a single layer within a textile preform or for multiple textile layers at once. The nonlinear and pressure-dependent behavior of the materials covered in the multiscale analysis is modeled with novel material models developed for this purpose. In order to avoid mesh-dependent solutions in the finite-element simulations, regularization techniques are applied. The simulations are compared to experimental test results.
