The mechanical properties of composites consisting of high-density polyethylene (HDPE) and oil palm empty fruit bunch (EFB) fiber are reported. Three sizes of EFB at different filler loadings were compounded with a single screw compounder. Modulus of elasticity (MOE) and modulus of rupture (MOR) of the EFB-HDPE composites increased and decreased, respectively, with increasing filler loading. Samples with smaller sized particles displayed higher MOE and MOR compared to the larger ones. Flexural toughness and tensile and impact strengths decreased as more filler was incorporated in the composite. Scanning electron microscope micrographs showed that the particles embedded in the matrix were in the form of irregular-shaped fiber bundles and the tensile failure occurred through extensive fiber bundles pull out and debonding.
ABSTRACT:The mechanical properties of composites consisting of high-density polyethylene (HDPE) and oil palm fibrous wastes-that is, empty fruit bunch (EFB)-have been investigated. Tensile modulus showed an increase, whereas tensile strength, elongation at break, and impact strength decreased with increasing filler loading. The strong tendency of EFB to exist in the form of fiber bundles and the poor filler-matrix interaction is believed to be responsible for the poor strength displayed by the composites. Attempts to improve these properties using two types of coupling agents, that is, 3-aminopropyltrimethoxysilane (3-APM) and 3-aminopropyltriethoxysilane (3-APE) and two types of compatibilizers, poly(propylene-acrylic acid) (PPAA) and poly(propyleneethylene-acrylic acid), (PPEAA), are described. While almost all chemical treatments increased the stiffness of the composites, limited improvement has been observed in the case of tensile strength. This have been attributed to the presence of fiber bundles that remain intact even after several types of chemical treatment have been carried out. Thus, the role of EFB as reinforcing agent is not fully realized. Scanning electron microscopy (SEM) micrographs revealed that the main energy-absorbing mechanisms contributing towards toughness enhancement is through the fiber bundle pull-out process.
The mechanical properties of composites consisting of high density polyethylene (HDPE) and oil palm frond (OPF) have been investigated. Three sizes of OPF at different filler loadings were compounded using a single screw compounder. Modulus of rupture (MOR) of the OPF-HDPE composites decreased with increasing filler loading. Samples with smaller size particles displayed higher MOR as compared to the larger ones. The incorporation of OPF into polymer matrix has also reduced the tensile and impact properties of the composites. This has been attributed to poor filler dispersion and increasing tendency for filler-filler interactions as filler loading increases. Scanning electron microscopy (SEM) has revealed that the OPF particles embedded in the matrix were in the form of irregular shaped-fibre bundles and the failure occurred through extensive fibre bundle pull-out and debonding. This failure mechanism has provided qualitative evidence for the poor tensile and impact strengths of the composites.
The mechanical properties of wood polymer composites consisting of polypropylene and mixed sawdust of meranti shorea spp. dominant and rice husk filler have been studied. Three different filler loadings of 50, 60, and 70 wt% were used and the process of compounding and extrusion was carried out using a twin-screw extruder. Increase in flexural modulus and tensile modulus are observed while tensile strength, elongation at break, flexural strength, and Izod impact decrease with increasing filler loading. Poor interaction between wood filler and the plastics is believed to be the main reason for the decreasing trend. Maleic anhydride grafted polypropylene (MAPP) was used in the formulation to improve the interfacial adhesion between the two components. Addition of the MAPP shows some improvement, particularly at 1%, and further increment of the MAPP did not show any significant impact on the properties tested.
In recent years, considerable attention has been paid to the research of dynamic response of long-span bridges with particular emphasis on seismic behavior. Cable-stayed and suspension bridges are the most popular types. Since long-span bridges have multi-supports and extreme lengths, due to the spatial variation effects, the ground motions at different supports might be non-uniform. A state-of-the-art update review of the response of long-span bridges subjected to non-uniform excitation is presented. The review mainly focuses on the theoretical aspects of non-uniform excitation, numerical studies, and experimental studies to verify some of the theoretical findings. In this paper, a review of the use of shake-table in experimental studies of long-span bridges is also presented. The non-uniform cases considered include a time delay with the same support excitations, multiple support excitations, and the combination of the first and the later. The results are discussed and summarized in comparison to the cases of uniform support excitation.
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