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Considering the boom in the market for wood plastic composite (WPC) products due to their relatively high specific strength properties, low maintenance costs, and wide range of applications, many authors have studied the performance of these composites prepared by reactive extrusion with different compatibilizers and peroxide types. This paper presents the density, chemical composition, and morphology of sawdust and the preparation and characterization of WPC with polypropylene by compression molding using different amounts of sawdust with and without coating with compatibilizer. Good-quality WPCs were obtained, as evident from almost identical experimental and theoretical density values of these composites. The WPCs prepared without compatibilizer coating exhibited low tensile properties. Irrespective of coating by different compatibilizers, the maximum tensile strength of all the WPCs decreased with increasing amount of sawdust. The WPCs prepared with uncoated sawdust fibers absorbed much more water than those prepared with compatibilizer-coated fibers, the latter showing increasing water intake with increasing amount of sawdust. These results are discussed in terms of melt-flow index, density differences, and adhesion between the sawdust and polypropylene.

Greater concern for environmental safety and fuel economy has increased interest in the use of renewable resources for development of new materials. Wood-plastic composites, made of recycled plastic and wood wastes, are very attractive in this respect, making this one of the most dynamic areas of new developments in the plastics industry in the past decade. This paper presents the preparation and characterization of polypropylene-sawdust composites by compression molding using maleated polypropylene (MAPP) produced in Brazil by reactive extrusion, with different amounts of two types of peroxides. The MAPP was characterized for thermal properties, melt flow index, and chemical structure, while the composites containing both uncoated and MAPP-coated sawdust were characterized for mechanical properties to understand the effect of coating as well as to compare these properties with those of composites prepared with commercial MAPP. The MAPP was efficient as a compatabilizer for polypropylene/sawdust composites. Better impact and tensile properties were observed in composites prepared with medium and high melt flow index compatibilizer concentrations, respectively.

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 This paper provides a case study of a real aeronautical safety-critical software development project under the DO-178C processes, where the COCOMO II method was applied as an estimation technique for the required software development effort. The main goal and contribution of the case study is to support the research on software effort estimation and provide software practitioners with useful data based on a real project. We collected the actual required effort for the project and then compared to the estimated values. The rationales for each scale factor and effort multiplier selection were also described in details. We found a Magnitude of Relative Error (MRE) of 31% and provided alternatives for future work in order to increase the effort estimation accuracy in safety critical software projects.