Abstract. Cellulose (CE), sawdust (SD) and wheat straw (WS) were subjected to triethoxysilane (AS) and methacriloxy propyl trimethoxy silane (MS), and maleic anhydride grafted polypropylene (MAPP) to improve interfacial bonding with matrix. Composites were prepared by these fibers as reinforcement. Tensile tests results show that composites were significantly enhanced by employment of coupling agents and MAPP to be the most effective coupling agent. Mechanical properties of SD composites exhibit the best performance compared to CE and WS. Optimum conditions for coupling agents were found to be 1 wt % for silane coupling agents and 5 wt % for MAPP.

Abstract. Surface treatment of three natural fibers including cellulose (CE), sawdust (SD) and wheat straw (WS) were carried out with triethoxysilane (AS), methacriloxy propyl trimethoxy silane (MS), and maleic anhydride grafted polypropylene (MAPP), respectively. Then the composites reinforced by these natural fibers were studied by water absorption and FTIR. It was found that water absorption decreased with employment of coupling agents. Among the coupling agents, MAPP exhibited the best performance in decreasing water absorption. In addition, FTIR analysis revealed the decrease in hydrophilicity of fibers with silane treatment and new bond formations with employment of MAPP.

 The surface modification effects of triethoxysilane (AS), methacriloxy propyl trimethoxy silane (MS), and maleic anhydride grafted polypropylene (MAPP) on the cellulose (CE), sawdust (SD) and wheat straw (WS) have been studied by tensile test at room temperature and fracture morphology observation on composites reinforced by these natural fibers. The results revealed that MAPP was the most effective coupling agent, and SD composites exhibit the best performance compared to CE and WS composites. Optimum conditions for coupling agents were found to be 1 wt % for silane coupling agents and 5 wt % for MAPP. SEM analysis confirmed tensile test results, proving better adhesion with the employment of MAPP. Void and crack formations around the fibers were observed to decrease with MAPP treatment. Silane treatment did not provide an observable enhancement in adhesion between fiber and matrix.

Elevated environmental awareness and an increasing concern with the global warming have stimulated the automotive, construction and packing industries to look for materials that can replace conventional synthetic fibers. Natural fiber appears as a good alternative since they are available in fibrous form and can be extracted from plant leaves, stalk, fruits and seeds at very low costs. In this study, the effect of sisal fiber surface treatment on mechanical properties was studied for natural sisal fibers. Sisal fibers were treated by alkali treatment, heat treatment and silane treatment respectively in order to enhance the interfacial adhesion of the fiber/polymer composite for mechanical properties improvement. Sisal fiber/polyethylene (PE) composites were prepared at fiber content of 10, 20, 30wt% by using twin screw extrude equipment and their mechanical properties such as tensile, flexural and impact strength were examined. Silane treated fiber (with content of 30%)reinforced composites showed 18% increase in tensile strength and 32% in Young's modulus, while the alkali treated fiber (with content of 30%)reinforced composites performed 37% increase in flexural strength. However, in case of impact strength, the treatment has been found to cause a reduction. It was also found with increasing fiber content, tensile strength, flexural strength and modulus of the PP composites increased but impact strength and elongation at break decreased.

Abstract.A free-standing TiAl based microlaminate sheet with thickness of 300 μm was deposited with high-power electron beam physical vapour deposition system. Microstructure and phase analysis of as-deposited samples were studied by XRD, SEM and TEM. Toughening by structure was analyzed with tensile test. The results show as-deposited sample was constituted of α2-Ti3Al and γ-TiAl and α-Ti. Alternation of rich aluminum zone and rich titanium zone are presented along cross section of TiAl depositing layer resulted from deviation of saturated vapor pressure between aluminum and titanium. After densification treatment, room-temperature tensile strength and elongation increased compared to that of as-deposited samples，reached 657 MPa and 2.95%, respectively. Tensile strength under high temperature exhibits an abnormal increase, exceeding 450 MPa at 1023K. The presence of ductile Ti layers can lead to cracks stagger along inter-laminar interfaces or crack deflection and the micro-bridge connection caused by ductile Ti layers, due to the TiAl-Ti3Al/α-Ti micro-laminate displaying a fine characteristic of delayed fracture.