خواص کشسان کامپوزیت های تقویت شده توسط فیبر شبکه ای
Abstract
1- Introduction
2- Numerical implementation
3- Numerical results
4- Analytical results
5- Discussion
6- Conclusions
References
Abstract
This research stems from the idea of introducing a fibre-network structure into composites aiming to enhance the stiffness and strength of the composites. A novel new type of composites reinforced by a tranversely isotropic fibre-network in which the fibres are devided into continuous segments and randomly distributed has been proposed and found to have improved elastic properties compared to other conventional fibre or particle composites mainly due to the introduction of cross-linkers among the fibres. Combining with the effects of Poisson’s ratio of the constituent materials, the fibre network composite can exhibit extraordinary stiffness. A simplified analytical model has also been proposed for comparison with the numerical results, showing close prediction of the stiffness of the fibre-network composites. Moreover, as a plate structure, the thickness of the fibre network composite is adjustable and can be tailored according to the dimensions and mechanical properties as demanded in industry.
Introduction
Fibre reinforced composites have been widely used in various fields for their attractive mechanical and physical properties with the wide choices of constituent materials and geometry structures. Numerous different structures of fibre composites, such as uni-directional fibre composites, cross-ply fibre composites, woven fabric composites and fibre laminates etc., have been designed and applied primarily for their advantages in directional mechanical properties. However, the superior properties are achieved by sacrificing the properties in other axial or planar directions. In addition, it is inevitable in engineering that loads are applied to the inferior directions of the structure. This may increase the risk of crack propagation and, even worse, fracture. For instance, delamination [1] is a common problem for laminate composites due to the weakly bonded interfaces between plies. The similar problem also exists even for the randomly distributed fibre composites which are mostly isotropic [2] or transversely isotropic [3]. Some three dimensional numerical models [2–4] of short fibre reinforced composites have been proposed by many researchers with the most frequently used method of random sequential adsorption (RSA). However, overlap between fibres are usually avoided which makes it difficult to generate a model with a high volume fraction. Besides, the constraints among fibres in the conventional fibre composites are weak since they are only, or at most, in contact but without bonding connection, thus rendering large deformation and easy pull-out [5] of fibres when subjected to load. It has been found that interpenetrating composites reinforced by a self-connected fibre-network have significantly enhanced mechanical properties, such as stiffness and strength, compared to their counterparts with discontinuously reinforced phase structures.