Review of the role of the interphase in the control of composite performance on micro- and nano-length scales

Jancar, J. (Institute of Materials Chemistry, Brno University of Technology)

Source: Journal of Materials Science, v 43, n 20, October, 2008, Stretching the Endurance Boundary of Composite Materials: Pushing the Performace Limit of Composite Structures, p 6747-6757

ISSN: 0022-2461 CODEN: JMTSAS

Publisher: Kluwer Academic Publishers

Abstract: In fiber reinforced composites (FRCs), exhibiting heterogeneous structure at multiple length scales, the interphase phenomena at various length scales were shown to be of pivotal importance for the control of the performance and reliability of such structures. Various models based on continuum mechanics were used to describe effects of the macro- and meso-scale interphase on the mechanical response of laminates and large FRC parts, satisfactorilly. At the micro-scale, the interphase is considered a 3D continuum with ascribed average properties. Number of continuum mechanics models was derived over the last 50 years to describe the stress transfer between matrix and individual fiber with realtively good success. In these models, the interphase was characterized by some average shear strength, τ a, and elastic modulus, E a. On the other hand, models for tranforming the properties of the micro-scale interphase around individual fiber into the mechanical response of macroscopic multifiber composite have not been generally successfull. The anisotropy of these composite structures are the main reasons causing the failure of these models. The strong thickness dependence of the elastic modulus of the micro-scale interphase suggested the presence of its underlying sub-structure. On the nano-scale, the discrete molecular structure of the polymer has to be considered. The term interphase, originally introduced for continuum matter, has to be re-defined to include the discrete nature of the matter at this length scale. The segmental immobilization resulting in retarded reptation of chains caused by interactions with solid surface seems to be the primary phenomenon which can be used to re-define term interphase on the nano-scale. Thus, the Rubinstein reptation model and a simple percolation model were used to describe immobilization of chains near solid nano-particles and to explain the peculiarities in the viscoleastic response of nano-scale "interphase." It has also been shown that below 5 nm, Bernoulli-Euler continuum elasticity becomes not valid and higher-order elasticity along with the proposed reptation dynamics approach can provide suitable means for bridging the gap in modeling the transition between the mechanics of continuum matter at the micro-scale and mechanics of discrete matter at the nano-scale. © 2008 Springer Science+Business Media, LLC. (53 refs.)

terms:  Three dimensional  -  ABS resins  -  Carbon fiber reinforced plastics  -  Continuum mechanics  -  Elastic moduli  -  Elasticity  -  Electric currents  -  Mechanical properties  -  Mechanics  -  Nanomechanics  -  Nanostructured materials  -  Nanotechnology  -  Quantum chemistry  -  Shear strength  -  Structure (composition)