Composites For Industrial Applications Research Articles

Barrier Screw Compounding and Mechanical Properties of EAA Copolymer and Cellulose Fiber Composite

Abstract The difficulty of feeding cellulose fibers and thermoplastics into the extruder or injection molding machine is addressed, this being a serious problem in the production of cellulose fiber composites for industrial applications. Agglomerates consisting in cellulose fibers and ethylene-acrylic acid copolymer (EAA) with different cellulose contents and different fiber lengths were processed with two different screws in order to better understand how the dispersion of the fibers can be improved by melt extrusion. A conventional screw with a compression ratio of 4:1 and a screw with barrier flights were used at different screw rotation speeds. The fiber length and fiber content were measured and microscopic analyses were performed in order to estimate the number and size of the cellulose fiber aggregates in the final composites. It was concluded that the barrier screw was more effective than the conventional screw in breaking up the fiber aggregates and dispersing the fibers. More but smaller cellulose aggregates were observed when the barrier screw was used, and the reduction of length was significantly greater for long than for short fibers. In contrast to that was expected, the samples containing the shorter fibers had better mechanical properties, probably due to a better dispersion of the fibers.

Crack identification in composite elements with non-linear geometry using spatial wavelet transform

A great popularity of constructional polymer composites in industrial applications requires the development of appropriate diagnostic methods for the elements made of these materials. These methods should provide damage detection and identification in possible early stages of its development. A large group of such methods is based on vibration testing and modal analysis. One of the promising techniques of processing vibration data for damage identification is a wavelet transform. Considering the practical needs the method should be applicable for plane structures with non-linear geometry. Results presented in this paper consider numerous analyses including the application of different types of wavelet transforms, different types of wavelet functions and other factors, which have an influence on the accuracy of damage identification. The proposed method shows good effectiveness in damage identification problems and could be applied in industrial conditions as well.

STONE-GROUND WOOD PULP-REINFORCED POLYPROPYLENE COMPOSITES: WATER UPTAKE AND THERMAL PROPERTIES

Two of the drawbacks of using natural-based composites in industrial applications are thermal instability and water uptake capacity. In this work, mechanical wood pulp was used to reinforce polypropylene at a level of 20 to 50 wt. %. Composites were mixed by means of a Brabender internal mixer for both non-coupled and coupled formulations. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the thermal properties of the composites. The water uptake behavior was evaluated by immersion of the composites in water until an equilibrium state was reached. Results of water absorption tests revealed that the amount of water absorption was clearly dependent upon the fiber content. The coupled composites showed lower water absorption compared to the uncoupled composites. The incorporation of mechanical wood pulp into the polypropylene matrix produced a clear nucleating effect by increasing the crystallinity degree of the polymer and also increasing the temperature of polymer degradation. The maximum degradation temperature for stone ground wood pulp–reinforced composites was in the range of 330 to 345 oC.

Dramatic property enhancement in polyetherimide using low-cost commerciallyfunctionalized multi-walled carbon nanotubes via a facile solution processingmethod

Polyetherimide (PEI) has excellent mechanical and thermal properties, and exceptional fireresistance. Developing even broader multi-functionality in PEI/carbon nanotube (CNT)composites for industrial applications is an alluring but challenging goal, due to processingdifficulties related to the high pressure and temperature needed to achieve effective flow forthis polymer, and costly and complex treatments of the CNTs. Here we report thefabrication of PEI nanocomposite films using low-cost commercially functionalizedmulti-walled carbon nanotubes (MWNTs), and a simple and innovative process, achievingexceptional properties with only 0.5 wt% of MWNTs, including an increase in electricalconductivity of 12 orders of magnitude, accompanied by an unprecedented increase of86 °C in thermal decomposition temperature (higher service temperature). Field emissionscanning electron microscopy revealed a high degree of uniform dispersion among theMWNTs, superb polymer–MWNT interaction and formation of a spatially homogeneousnanotube network within the matrix. The enhancement in these properties suggests greatpotential use for this developed processing approach and the resulting nanocomposites formulti-functional coating or interfacing materials in aerospace and electronic industries.

Industrial applications of natural fibres advanced composites: environmental effects and comparative Life Cycle Analysis

Natural fibres composite materials can have an important role for the planet sustainability. The use of such materials involves the following considerations: complete biodegradability; no toxic agents; no fabrication energy consumption (very low emissions). The purpose of this paper is to evaluate the Life Cost Analysis (LCA) of natural fibres composites for industrial applications, for making a comparison with those relative to steel, aluminium and glass fibres production. The comparison shows all the important advantages that we can obtain by the (partial) substitution of such materials with the new natural fibres composites, depending on the applications.

Design aspects of processing of aluminium 6061 based metal matrix composites via powder metallurgy

AbstractAcceptance of metal matrix composites for industrial applications depends upon improving properties using an economic production route, which includes the processing design. Two powder metallurgical routes have been used in the manufacture of Al 6061 metal matrix composites. The first involves blending, vacuum canning, and hot pressing from prealloyed powders and the second involves blending of elemental powders, liquid phase sintering, and subsequent hot rolling. These composites comprise 7·5 or 15 vol.-% of 7, 23, or 45 μm SiC particles. In this paper, the composite microstructure at each stage of the different processing routes has been examined and the aging behaviour investigated. Effects on the tensile properties of fabrication techniques, SiC particle size, and volume fraction are presented and discussed.MST/3020