Fabrication Mechanical Properties of Unidirectional Jute/PP Composites Using Jute Yarns by Film Stacking Method

This paper mainly focuses on the fabrication process of long fibre reinforced unidirectional thermoplastic composites made using both natural (untreated) treated jute yarns. Jute yarns were wound in layers onto a metallic frame. Polypropylene films were inserted between these layers and compression moulded to fabricate unidirectional jute/PP composite specimens. Static mechanical properties were evaluated from tensile three point bending tests. Pre- post-failure examination were carried out on the test specimens using optical scanning electron microscopy to analyse the test results and investigate the correlations between their impregnation state, processing conditions, mechanical performances and fracture morphologies. For the unidirectional jute/PP film-stacked composites, the results indicated that the processing condition at the moulding temperature of 160°C and moulding pressure of 2.0 MPa for 15 min was ideally suited to obtain optimized properties. Improved wettability of resin melts due to complete matrix fusion at this processing condition facilitated thorough impregnation with minimum microstructural imperfections (microvoids) being generated. Jute/PP composites that contained treated jute yarns have shown superiority in tensile bending properties. Jute yarns polished or coated with PVA/PP (polyvinyl alcohol/polypropylene) must have contributed positively to fibre/matrix interfacial interactions leading to matrix to fibre effective stress transfer, thereby improving their reinforcing effects. Tensile strength and modulus of PP resin increased by approximately 285% and 388%, respectively, due to 50 wt% reinforcement by natural jute yarns. Further improvements in strength and modulus were achieved by approximately 14% and 10%, respectively, when treated yarns were used . The maximum bending stress modulus of jute/PP composites containing untreated yarns were approximately 190% and 460% higher than those of the virgin PP materials, and bending properties were improved by further 11% and 23%, respectively, due to coating treatments on the yarn surface.     

Modifying glass fiber surface with grafting acrylamide by UV-grafting copolymerization for preparation of glass fiber reinforced PVDF composite membrane

Experimental design and response surface methodology(RSM) were used to optimize the modification of conditions for glass surface grafting with acrylamide(AM) monomer for preparation of a glass fiber reinforced poly(vinylidene fluoride)(PVDF) composite membrane(GFRP-CM). The factors considered for experimental design were the UV(ultraviolet)-irradiation time, the concentrations of the initiator and solvent, and the kinds and concentrations of the silane coupling agent. The optimum operating conditions determined were UV-irradiation time of 25 min, an initiator concentration of 0–0.25 wt.%,solvent of N-Dimethylacetamide(DMAC), and silane coupling agent KH570 with a concentration of 7 wt.%. The obtained optimal parameters were located in the valid region and the experimental confirmation tests conducted showed good accordance between predicted and experimental values. Under these optimal conditions, the water absorption of the grafted modified glass fiber was improved from 13.6% to 23%; the tensile strength was enhanced and the peeling strength of the glass fiber reinforced PVDF composite membrane was improved by 23.7% and 32.6% with an AM concentration at 1 wt.% and 2 wt.%. The surface composition and microstructure of AM grafted glass fiber were studied via several techniques including Field Emission Scanning Electron Microscopy(FESEM), Fourier transform infrared spectroscopy-attenuated total reflectance(FTIR-ATR) and energy dispersive X-ray spectroscopy(EDX). The analysis of the EDX and FTIR-ATR results confirmed that the AM was grafted to the glass fiber successfully by detecting and proving the existence of nitrogen atoms in the GFRP-CM.     

碳纤维环氧复合材料火灾危险综合评价

碳纤维环氧复合材料是目前航空领域中应用最为广泛的结构材料之一,但其本身具有可燃性,一旦起火,会严重危及飞机结构安全。建立碳纤维环氧复合材料火灾评价体系,以层次分析法为基础,结合锥形量热仪试验数据对3种典型的碳纤维环氧复合材料的火灾危险性进行了综合评价。通过理论分析和试验测试得到FGI(火势增长指数)、THRI_(4min)(放热指数)、TSPI_(4min)(发烟指数)和ToxPI_(4min)(毒性气体生成速率指数)4个火灾危险性评价指数,能够很好地量化典型碳纤维环氧复合材料的火灾危险性,FGI能更好地辨识碳纤维环氧复合材料的火灾危险性。结果表明,双向碳纤维布和单向碳纤维预浸料的火灾危险性接近,表明织造方式的不同对火灾危险性影响很小,而碳纤维夹层板的火灾危险性相对较大。轻型飞机仪表箱部位相对于仪表板和机身框,火灾危险性较大,对此部位的防火应提出更高的要求。     

Si(B)CN 陶瓷及其复合材料评价与应用研究现状

总结了近年来Si(B)CN陶瓷及其复合材料评价与应用研究现状。首先介绍了Si(B)CN陶瓷及其复合材料的制备,而后详细综述了Si(B)CN陶瓷及其复合材料在力学性能、氧化行为、烧蚀行为、疲劳与蠕变性能、环境性能等方面的性能评价,并对其应用现状进行了概述。     

基于绿色合成法的纳米铁/活性碳复合材料对甲基橙的降解动力学研究

为了综合处理废水中的甲基橙,以绿茶萃取液为还原剂、活性炭为载体,采用液相还原法绿色合成了纳米铁/活性炭复合材料,研究了活性炭投放量、甲基橙溶液的初始浓度、溶液初始p H值及反应时间对甲基橙去除率的影响,探讨了不同影响因素下甲基橙的降解动力学。结果表明:甲基橙的降解反应近似符合一级反应动力学,反应速率常数为0.0047~0.0158 L/(mol·min)。在纳米铁/活性炭复合材料去除甲基橙的过程中,通过纳米铁的还原和活性炭的吸附共同作用,其中纳米铁对甲基橙的降解起主要作用。     

Use of recycled plastics in wood plastic composites – A review

The use of recycled and waste thermoplastics has been recently considered for producing wood plastic composites (WPCs). They have great potential for WPCs manufacturing according to results of some limited researches. This paper presents a detailed review about some essential properties of waste and recycled plastics, important for WPCs production, and of research published on the effect of recycled plastics on the physical and mechanical properties of WPCs.     

基于ABAQUS的复合材料低速冲击损伤分析

目的分析不同冲击能量对复合材料层合板的损伤情况,验证有限元模型的合理性和有效性。方法以CCF300/10128H型碳纤维树脂基复合材料层合板为研究对象,采用落锤冲击试验机对层合板进行冲击实验,然后对冲击后的试验件进行超声C扫描。建立有限元模型,运用ABAQUS软件对冲击过程进行模拟。结果有限元模拟结果与实验结果吻合良好。结论复合材料层合板内部损伤随着冲击能量的增大而快速变大。出现穿透损伤以后,损伤趋于平缓,有限元模型能够较好地预测复合材料低速冲击损伤。     

g-C3N4/Bi2S3复合物的制备及可见光催化降解MO

采用简单溶剂热方法成功合成可见光催化剂g-C_3N_4/Bi_2S_3.合理地利用X射线衍射(XRD)、傅立叶红外光谱分析仪(FTIR)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM、HRTEM)、紫外可见漫反射光谱(UV-vis DRS)等表征手段对合成的样品进行了表征.与纯g-C_3N_4和Bi_2S_3相比,g-C_3N_4/Bi_2S_3复合物对甲基橙(MO)的可见光催化降解具有更高的降解效率.根据能带分析结果,电子-空穴对的有效分离增强了光催化效率.此外,提出了g-C_3N_4/Bi_2S_3对MO的光催化降解过程以阐明降解机制.提供了一种经济简单并易于规模化扩大开发可见光响应催化剂的方法,并在废水处理中具有潜在的应用价值.     

Biodegradation of Compostable Plastics in Green Yard-Waste Compost Environment

Compostable plastic materials, produced from polylactic acid (PLA), corn starch, or sugarcane, degraded in a green yard-waste compost environment. The compostable plastics claim to meet ASTM D6400 standards for biodegradation, sustainable plant growth, and eco-toxicity. Biodegradation was measured by disintegration studies over 20 weeks. The commercially available compostable products, made from PLA, sugarcane, or corn starch, biodegraded while in a commercial compost facility with other common yard waste compostable items. The PLA container, cup, and knife completely degraded in 7 weeks at a rate similar to the Avicell micro-cellulose control. The corn starch-based trash bag and sugarcane plate degraded at a similar rate as the Kraft paper control. The three materials degraded between 80% and 90% after 20 weeks.     

Starch-Based Polymers in Extrusion Coating

The starch-based polymers exhibited shear thinning and elastic nature in rheological characterizations. Thin coatings with narrow neck-in could be produced at fairly high extrusion coating line speeds. Adhesion between the starch-based polymers and paperboard was typically weak. Water vapor barrier of starches was very poor. Soft starch grades had a good pinhole resistance and a good heat sealing performance. Brittle nature of starch caused cracking as the coated paperboards were creased.