Nano-structured interpenetrating composites with enhanced Young’s modulus and desired Poisson’s ratio

Abstract

This paper has demonstrated that interpenetrating composites could be designed to not only have an significantly enhanced Young's modulus, but also have a Poisson's ratio at a desired value (e.g. positive, or negative, or zero). It is found that when the effect of the Poisson's ratio is absent, the Young's modulus of interpenetrating composites is closer to the Hashin and Shtrikman's upper limit than to their lower limit, and much larger than the simulation and experimentally measured results of the conventional isotropic particle or fibre composites. It is also illustrated that at the nanoscale, the interphase can either strengthen or weaken the stiffness, and the elastic properties of interpenetrating composites are size-dependent.

Auxetic interpenetrating composites: A new approach to non-porous materials with a negative or zero Poisson’s ratio

“…In order to enhance the auxetic behaviour (i.e., a large negative Poisson's ratio), a relatively high value of ⁄ is desired. The elastic properties of composites can be significantly affected by the Poisson's ratio of the matrix material [15][16][17], but are less sensitive to that of the reinforcement material (this may be because the volume fraction of the latter is usually much smaller). As almost all the singlephase solid isotropic materials have a positive Poisson's ratio, a very small Poisson's ratio is desired for the matrix material in order to enhance the auxetic behaviour of the composites.…”

“…With the advance in materials syntheses, experimental measurements and computational simulations, it has been recognised that Poisson's ratio is related to the densification, connectivity, ductility and the toughness of solid materials [14]. It has also been found that the elastic properties of a composite material can be largely affected, thus tuned by the Poisson ratios of the constituent materials [15][16][17]. Cellular materials are often used as filler in sandwich structures.…”

“…Cellular materials are often used as filler in sandwich structures. Compared to the conventional foam fillers, auxetic materials with a negative Poisson's ratio can enhance the stiffness [15,16], indentation resistance [18,19], crashworthiness, energy absorption performance [20][21][22], and fracture toughness [23] of sandwich structures.…”

“…When high stiffness/weight ratio, high strength and energy absorption are all demanded, solid composite materials may be a good choice. Compared to the conventional particle reinforced and unidirectional fibre reinforced composites [31][32][33][34], interpenetrating phase composites (IPCs) reinforced by a self-connected network rather than by separated particles or fibres, have been demonstrated to have much better mechanical and physical properties [16,17,[35][36][37][38] than those of their conventional counterparts. When a self-connected auxetic lattice structure or fibre-network is embedded as reinforcement in a matrix with a low positive Poisson's ratio, the composite would have the potential to exhibit auxetic behaviour.…”

The elastic properties of composites reinforced by a transversely isotropic random fibre-network

“…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 [6][7][8][9][10][11]. Apart from the improved mechanical properties, good thermal and electrical conductivities [12,13] can also be an advantage for fibre network composites owing to the connected network of fibres.…”