Composite characteristics reinforcement effects

N/inm. Composites reinforced with lyocell 6.7 and lyocell 15.0 multilayer webs reached values of 36 N/mm and 28 N/mm respectively. For the needle felt reinforced composites clear reinforcement effects were determined (lyocell 1.3-PLA = 63 N/ mm, lyocell 6.7-PLA = 61 N/mm and lyocell 15.0-PLA = 57 N/mm ). These results lead to the assumption that the kind of the semi-finished product has a clear influence on the mechanical characteristics of the composites produced by the compression molding technique CP-1. This effect could be attributed to a more homogeneous fiber distribution in the PLA matrix due to the additional needling process and the lower thickness of the needle felts compared to the multilayer webs. It is assumed that the lower thickness lead already in the pre-heating phase to a better heat conductivity and drying in the press. 

The increase in magnetic properties of vulcanized NR clearly shows that the ferromagnetic characteristics of nickel particles are retained in the composites. The elastic modulus of the samples shows improvement as the nickel content in the composites increases. The increase in the strains modulus as the amount of nickel increases reflects the reinforcing effect of nickel nanoparticles in NR matrix. However, there is a monotonous decrease in elongation at break with the increase in filler loading. This may be due the formation of agglomerates of filler particles in the NR matrix. 

The most important filler characteristics determining the properties of PP composites are particle size, particle size distribution, specific surface area and shape. None of these influence stiffness very much the reinforcing effect is a result of the orientation of the anisotropic particles. All other properties are considerably affected by these filler characteristics. Yield stress and strength usually increase with decreasing particle size and increasing surface area, while deformability and impact resistance change in the opposite direction. 

A traditional chemical extraction process that uses an alkaline sodium hydroxide solution has also been applied to the same wooden material. Fibers extracted by the two methods have been used as reinforcement for the two commercial polypropylenes the conventional isotactic polypropylene, and maleic anhydride functionalized isotactic polypropylene (iPPMA). The composites have also been subjected to a water absorption treatment. To assess the reinforcement effect of fibers, composite characterization techniques and determination of mechanical properties have been performed with particular attention to the fiber-matrix interfacial characteristic. The results have been compared with those of short glass reinforced polypropylene composites. 

The temperature dependence of the Payne effect has been studied by Payne and other authors [28, 32, 47]. With increasing temperature an Arrhe-nius-like drop of the moduli is found if the deformation amplitude is kept constant. Beside this effect, the impact of filler surface characteristics in the non-linear dynamic properties of filler reinforced rubbers has been discussed in a review of Wang [47], where basic theoretical interpretations and modeling is presented. The Payne effect has also been investigated in composites containing polymeric model fillers, like microgels of different particle size and surface chemistry, which could provide some more insight into the fundamental mechanisms of rubber reinforcement by colloidal fillers [48, 49]. 

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