Mechanical properties interfacial stress distribution

The gap between the predictions and experimental results arises from imperfect dispersion of carbon nanotubes and poor load transfer from the matrix to the nanotubes. Even modest nanotube agglomeration impacts the diameter and length distributions of the nanofillers and overall is likely to decrease the aspect ratio. In addition, nanotube agglomeration reduces the modulus of the nanofillers relative to that of isolated nanotubes because there are only weak dispersive forces between the nanotubes. Schadler et al. (71) and Ajayan et al. (72) concluded from Raman spectra that slippage occurs between the shells of MWNTs and within SWNT ropes and may limit stress transfer in nanotube/polymer composites. Thus, good dispersion of CNTs and strong interfacial interactions between CNTs and PU chains contribute to the dramatic improvement of the mechanical properties of the... 

Concrete is a composite typically composed of aggregate and cement paste. It is the connection between these phases - the interfacial transition zone (ITZ) that is most important.. The ITZ is the weakest link in the composite system with lowest mechanical properties of the three [1-4], The ITZ can affect the overall elastic module and the stress distributions in a concrete material. The ITZ is comparatively more porous than that of bulk cement paste, and often less well bonded to the aggregate [3]. This region can have a low formation of calcium-silicate-hydrate (C-S-H gel), a product of Portland cement hydration responsible for the good mechanical properties and durability [5]. 

In regards to the studies on transcrystalhnity in conventional fiber reinforced composites, their number is vast. A number of issues are related to the formation and growth of TCL [81] crystallinity of the matrix, mismatch of thermal coefficients of the fiber and the matrix, epitaxy between the fiber and the matrix, surface toughness, thermal conductivity, treatment of fiber, etc. Processing conditions such as cooling rate, temperature, and interfacial stress were also found to be important. There are indications that the TC phenomenon is probably too specific for each fiber/matrix system. Nevertheless, it has been recognized that the orientation distribution of the polymer chains in the TCL wUl determine the nature and extent of its effect on the mechanical properties of the composite material [84]. 

Most polymers are immiscible with each other. When two or more immiscible polymers are melt blended, without any planned compatibilization process, the components of the blend form different phases, which are separated from each other in the final product. This phase separation is due to the high surface tension between the immiscible polymer components in the interface region. The compatibilization of an immiscible polymer blend relies on the reduction of this interfacial tension. Normally, a blend that has been compatibilized can still be phase separated, but with a finer, stabilized dispersion of minor phase in the matrix. Improvement in mechanical properties of compatibilized blends are often observed due to a better adhesion between different phases and/or a better stress distribution in the solid state morphology when the material is under stress. 

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