Experimental characterization and modeling stiffness of polymer/clay nanocomposites within a hierarchical multiscale framework

Abstract

To provide a better understanding of the relationship between nanostructure and overall material stiffness in the case of polymer/clay nanocomposites, both analytical and finite element modeling were considered. A micromechanical analytical approach based on a multiscale framework is presented in which special attention is devoted to the constrained region around reinforcements. The thickness of the constrained region is seen as a characteristic length scale and the effect of particle size is explicitly introduced in the model. Moreover, the constrained region presents graded properties. The hierarchical morphology of intercalated silicate stacks is also explicitly introduced in the micromechanical model from an equivalent stiffness method in which the silicate stacks are replaced by homogeneous particles with constructed equivalent anisotropic stiffness. The orientational averaging process is used to derive the overall stiffness tensor of nanocomposite materials containing randomly oriented reinforcements. The respective influence of volume fraction, aspect ratio, size and orientation of the reinforcements, matrix properties, number of silicate layers per stack, and interlayer spacing on the overall nanocomposite stiffness is analyzed. The overall stiffness of polymer/clay nanocomposite systems is also evaluated by means of finite element simulations and the results compare favorably with model predictions. From an experimental point of view, relevant morphological and mechanical data were obtained on polyamide-6 nanocomposites prepared using a modified montmorillonite Cloisite 30B and an unmodified sodium montmorillonite Cloisite Na þ . The amount of constrained region around reinforcements was estimated using results issued from dynamic mechanical analyses and differential scanning calorimetry. Comparison to the model clearly underlines the contribution of the constrained region to the stiffness improvement.

On the overall elastic moduli of polymer–clay nanocomposite materials using a self-consistent approach. Part II: Experimental verification

“…Wang and Pyrz [2], Sheng et al [9], Luo and Daniel [10], and Mesbah et al [11] recently applied Eshelby-type micromechanical formulations to polymerclay nanocomposites. The main result of these investigations is the demonstration that models issued from the continuum mechanics framework can provide accurate predictions of the overall elastic properties of such materials so long as the morphology is accounted for.…”

“…Indeed, the constrained region is often introduced in models to incorporate explicitly the interactions between clay and matrix, and thus improve the modeling capabilities (e.g. [11,15,16]). The obtained results with our formulation show that the real contribution of the constrained region on the macroscopic stiffness seems difficult to assess.…”

Elastic and yield behaviors of recycled polypropylene-based composites: Experimental and modeling study

“…E ref PP=EOCi =E ref im is calculated at first by using Equation (14). Then, the contribution of talc to the stiffness of PP/EOC/Talc is obtained by considering the PP/EOC as the matrix.…”

On variations of the interphase thickness and the slope of strengthening by clay addition in exfoliated polymer-clay nanocomposites

“…Therefore, we summarize a combination of predicted data by dynamic mechanical analysis, nano indentation tests and molecular dynamics predictions. Mesbah et al [29] have employed differential scanning calorimetry and dynamic Sikdar et al [14] have utilized atomic force microscopy and nano-indentation tests to estimate the [These parameters were related to the constituents of the PCN system (see Table 1) and were derived with assumption of randomness in nanoclay distribution. In case of NYLON6_MMT system these parameters were reported in Table 2.…”