Fibre reinforced organic rectorite/unsaturated polyester composites

Three series of glass fibre (F) reinforced unsaturated polyester (UP)/organic rectorite (OREC) (F/UP/OREC) composites were manufactured by selecting two types of fibres, different gelation time of UP matrix and different content of OREC. The morphologies of F/UP/OREC composites were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dispersion of OREC in the cured UP matrix was investigated using transmission electron microscopy (TEM). The mechanical properties of UP/OREC and F/UP/OREC composites were evaluated. Additionally, the hot–wet resistance and alkali resistance of UP/OREC and F/UP/OREC composites were investigated. The mechanical properties and the resistance to hot–wet and alkali of UP composites can be improved by adding appropriate OREC without reference to the gelation time of UP matrix or the type of F. The maximum mechanical properties of UP composites can be obtained by adding 2 wt% OREC due to the high stiffness and uniform dispersion of OREC.     

Flexural properties of hemp fibre reinforced polylactide and unsaturated polyester composites

In this work, flexural strength and flexural modulus of chemically treated random short and aligned long hemp fibre reinforced polylactide and unsaturated polyester composites were investigated over a range of fibre content (0-50 wt%). Flexural strength of the composites was found to decrease with increased fibre content; however, flexural modulus increased with increased fibre content. The reason for this decrease in flexural strength was found to be due to fibre defects (i.e. kinks) which could induce stress concentration points in the composites during flexural test, accordingly flexural strength decreased. Alkali and silane fibre treatments were found to improve flexural strength and flexural modulus which could be due to enhanced fibre/matrix adhesion.     

Development of kenaf-glass reinforced unsaturated polyester hybrid composite for structural applications

The main aim of this paper is to develop kenaf-glass (KG) fibres reinforced unsaturated polyester hybrid composite on a source of green composite using sheet moulding compound process. Unsaturated polyester resin (UPE) and KG fibres in mat form were used at a ratio of 70:30 (by volume) with treated and untreated kenaf fibre. The kenaf fibre was treated with 6% sodium hydroxide (NaOH) diluted solution for 3 h using mercerization method. The hybrid composites were tested for flexural, tensile and Izod impact strength using ASTM D790-03, ASTM D618 and ASTM D256-04 standards respectively. The highest flexural, tensile and impact strength were obtained from treated kenaf with 15/15 v/v KG fibres reinforced UPE hybrid composite in this investigation.Scanning electron microscopy fractography showed fibre cracking, debonding and fibre pulled-out as the main fracture mode of composites and kenaf treated 15/15 v/v KG reinforced hybrid composite exhibited better interfacial bonding between the matrix and reinforcement compared to other combinations.     

Water absorption characteristics of aluminised E-glass fibre reinforced unsaturated polyester composites

Novel aluminised E-glass fibre reinforced unsaturated polyester composites, originally formulated for enhanced thermal and electrical shielding properties were evaluated in terms of their water absorption. One of the major obstacles delaying the acceptance of novel composites in engineering applications is the degradation of the polymer matrix material by moisture, which effects the physical and mechanical performance over time. The objective of this study was to characterise and quantify the degree of water absorption of novel aluminised E-glass reinforced unsaturated polyester composites. Aluminised E-glass composites were compared alongside their unmetallised E-glass counterparts. Two sets of temperature were used for this study. Results show that aluminised E-glass significantly reduces the saturation point compared to unmetallised E-glass. The differences between aluminised and unmetallised are correlated to fibre coatings. At elevated temperatures the aluminised E-glass sample is unstable and exhibits significantly higher water absorption indicating that a new failure mechanism is occurring.     

Behaviour of composite soil reinforced with natural fibres

Next to the food shortage, the housing shortage is one of the most crucial problems on earth. To improve this situation and make it possible to build more houses, particularly for low-income families, it is necessary to examine all locally available materials which can be used for construction. Bamboo, sisal and coconut fibres are materials which are available in abundance in Brazil and are not used in civil construction. To increase the amount of information concerning the physical and mechanical behaviour of these materials several research programmes were executed at Pontifical Universidade Católica in Rio de Janeiro (PUC-Rio) and Universidade Federal da Paraiba (UFPb) under the general supervision of the first author. In this paper new results are presented concerning the application of sisal and coconut fibres in conjunction with three types of locally appropriate soil for the production of composite soil blocks reinforced with sisal and coconut fibres.     

Water absorption study on pultruded jute fibre reinforced unsaturated polyester composites

Water absorption of natural fibre plastic composites is a serious concern especially for their potential outdoor applications. In this research, jute fibre reinforced with unsaturated polyester composites are subjected to water immersion tests in order to study the effects of water absorption in its mechanical properties. Water absorption tests were conducted by immersing composite specimens into three different environmental conditions included distilled water, sea water and acidic solutions at room temperature for a period up to 3 weeks. Water absorption curves obtained and characteristic parameter D (diffusion coefficient) and M_m (maximum moisture content) were determined. The water absorption of jute fibre reinforced unsaturated polyester composites were found to follow a so-called pseudo-Fickian behaviour. The effects of the immersion treatment on the flexural and compression characteristics were investigated. The flexural and compression properties were found to decrease with the increase in percentage water uptake. These flexural and compression behaviours were explained by the plasticization of the matrix–fibre interface and swelling of the jute fibres.     

Interfacial behaviour from pull-out tests of steel and aluminium fibres in unsaturated polyester matrix

This study aims at implementing an interfacial model to capture the role of interfaces in polyester-based composites reinforced by metallic fibres. A pull-out test of single aluminium and steel fibres embedded in unsaturated polyester matrix is performed. Finite element computation is performed to simulate the typical response of the pull-out test based on an interfacial model. The implemented model relies on a nonlinear relationship assumed between the interfacial shear and interfacial separation. A sensitivity analysis is conducted to reveal the effect of each parameter of the interfacial model. The identification of these parameters with respect to the experimental conditions is also attempted. The predictions show a perfect matching with the experimental trends if a two-term expression is accounted for as an interfacial response. The model outcome reveals superior interfacial performance of the aluminium/unsaturated polyester composite.     

天然细菌纤维素增强不饱和聚酯树脂复合材料的制备及性能

将天然纤维-细菌纤维素（BC）作为增强材料加入不饱和聚酯树脂（UPR）基体中,采用RTM工艺制备BC/UPR复合材料,并对其力学性能、吸湿性能进行了研究。通过紫外辐照方法探讨了BC/UPR复合材料的降解性能。研究结果表明:通过对细菌纤维素的表面改性,在亲水性的天然纤维和疏水性的高聚物基体之间形成了化学键结合,提高了BC/UPR复合材料的力学性能;BC纤维体积分数的增加也有助于提高力学性能, 当纤维体积分数为20%时,该复合材料拉伸强度最高可达152.9MPa; BC/UPR复合材料的吸湿过程符合Fick定律,吸湿可导致力学性能下降; BC/UPR复合材料吸收光能后,表面含氧官能团数量增加,发生一定程度的光降解。      

Mechanical property improvement of unsaturated polyester composite reinforced with admicellar-treated sisal fibers

Sisal fiber was treated by admicellar polymerization with a poly(methyl methacrylate) film coating in order to enhance the interfacial adhesion of the fiber/polymer composite for mechanical property improvement. Properties of the admicellar-treated sisal fiber were investigated by measuring its moisture absorption and electrostatic charge. Thermal stability study by thermogravimetric analysis and film identification by FTIR was also carried out. The treatment was shown to improve the tensile and flexural properties, impact strength, and hardness of the composite. SEM micrographs of the tensile fracture surface of sisal/unsaturated polyester composites also show interfacial adhesion improvement of the composite prepared with admicellar-treated sisal.     

Wettability of glass fibres with different sizings and their adhesion to unsaturated polyester matrices

The wetting characteristics of unsaturated polyester resins on glass fibres with different sizings have been studied by contact angle determination periods. The styrene content of the matrix and the nature of the coatings result to be determinant in the wettability of glass fibres by the polyester matrices. Highest styrene content and styrene-soluble-coatings determine better wetting characteristics. Mechanical properties of the cured specimens and scanning electron microscopy on the fracture surfaces were also performed. Interesting correlations between the nature of the sizing agent and cohesive energy density with mechanical properties and fibre/matrix adhesion were found.[/p]     

The low velocity impact response of non-woven hemp fibre reinforced unsaturated polyester composites

Hemp fibre reinforced unsaturated polyester composites (HFRUPE) were subjected to low velocity impact tests in order to study the effects of non-woven hemp fibre reinforcement on their impact properties. HFRUPE composites specimens containing 0, 0.06, 0.10, 0.15, 0.21 and 0.26 fibre volume fractions (V_f) were prepared and their impact response compared with samples containing an equivalent fibre volume fraction of chopped strand mat E-glass fibre reinforcement. Post-impact damage was assessed using scanning electron microscopy (SEM). A significant improvement in load bearing capability and impact energy absorption was found following the introduction hemp fibre as reinforcement. The results indicate a clear correlation between fibre volume fractions, stiffness of the composite laminate, impact load and total absorbed energy. Unreinforced unsaturated polyester control specimens exhibited brittle fracture behaviour with a lower peak load, lower impact energy and less time to fail than hemp reinforced unsaturated polyester composites. The impact test results show that the total energy absorbed by 0.21 fibre volume fraction (four layers) of hemp reinforced specimens is comparable to the energy absorbed by the equivalent fibre volume fraction of chopped strand mat E-glass fibre reinforced unsaturated polyester composite specimens.     

基于掺杂型不饱和聚酯的可调谐F-P腔的研究

将分散红 1(DR1)掺杂的不饱和聚酯(UP)树脂充入F- P腔中,在极化的同时进行热交联,制得了具有一定电光效应的非线性光学不饱和聚酯。研究了温度、引发剂和分散红 1 的含量对不饱和聚酯凝胶和固化时间的影响。随着分散红 DR1 含量的增加,体系的凝胶时间减少,固化时间增加,当 DR1 量>5%时,凝胶时间很短而固化时间却很长,已不适宜进行极化。随着树脂中过氧化苯甲酰(BPO)加入量的增加或温度的升高,体系的凝胶和固化时间缩短。将其制成器件后,发现其电光系数衰减性能与文献报道的掺杂型光交联不饱和聚酯和某些柔性主链的侧链型 NLO聚合物相当,而比PMMA/DR1掺杂体系的衰减小得多,其光损耗基本能满足器件化的需要,而其器件制作工艺性能大大改进,明显优于传统的旋涂法。极化后整个F- P腔的光损耗为 5dB,电光系数 r33 为 9pm/V,最大衰减量为 52%。此类材料和极化方法适合于制作可调谐F- P腔型光开关。     

Friction and wear of friction composites reinforced by natural fibres

In the present work, friction material composites were proposed to be used as automotive friction materials. The composites were reinforced by agricultural fibres of corn, palm, and sugar bars. The conventional friction materials based on asbestos cause serious lung diseases and being cancerous potential. The aim of the present work is to replace them by the proposed composites because they are environmentally friendly friction material for brake lining and clutch facings. Agricultural wastes of sugar bars, corn and palms fibres were prepared to obtain fibres of length less than 5 mm. The fibre materials were mixed by carbon, barium sulfate, silica, metallic powders and phenol formaldehyde. The proposed composites were pressed in the die at 105°C temperature. The produced specimens were subjected to machining processes to obtain the cylindrical form of 8 mm diameter. Experiments were carried out using test rig designed and manufactured to measure both friction and wear. It consists of a rotating hollow flat disc made of carbon steel, with an outside diameter of 250 mm and 16 mm thickness. The experiments investigated the effect of agriculture fibre wastes (corn, sugar bars, and palms fibres) on friction coefficient and wear. Wear mechanisms of the proposed composites were characterized by scanning electronic microscopy. The tribological properties of the proposed composites materials were compared to three commercial brake linings. Based on the experimental results it was found that, addition of agriculture fibre wastes (corn, sugar bars, and palms fibres) to composites materials increased friction coefficient and decreased wear. Friction coefficient slightly increased, while wear drastically decreased with increasing fibres content. The maximum friction value (0.58) was obtained by composites containing 30 wt.% iron and 25 wt.% sugar bar fibres. The corn fibres were more compatible with aluminum powder where it gave the highest friction coefficient and relatively lower wear compared to other composites. Wear resistance of the tested composites containing bunches and aluminum represented the lowest values among composites containing corn and bunches fibres. The lowest wear values were observed for composites containing 25 wt.% corn fibres and 30 wt.% aluminum and composites containing 20–25 wt.% sugar bar fibres.     

New formulations for unsaturated polyester resins and their interactions with low-profile agents and glass fibres

Special anhydrides, such as hexahydrophthalic, methyl-hexahydrophthalic, nadic, methylnadic and methyl-tetrahydroxyphthalic, have been polycondensed with glycols such as propylene and di-propylene, to obtain new formulations for unsaturated polyesters. The properties of these resins, such as tensile behaviour and ultraviolet resistance, neat or mixed with anti-shrinkage additives have been examined and compared to standard polyester resins. Particular attention was paid to the study of the influence of low-profile agents on the resulting phase structures of cured systems. Moreover, the role played by the different phases on the fibre/matrix addition in composite materials reinforced with coated glass fibres was also investigated.     

Hygrothermal effects of glass fiber reinforced unsaturated polyester resin composites aged in steady and fluctuating conditions

This paper presents the water uptake and its effect on the tensile properties and the translaminar fracture toughness of glass fiber reinforced unsaturated polyester composites (GFRUPs) aged in distilled and saltwater at a temperature of 50 °C, in steady and fluctuating conditions. In both conditions, the GFRUPs aged in distilled water absorbed more water than in saltwater. The tensile strength of GFRUP tends to decrease with the immersion time in both aging media, but the decrease of tensile strength in saltwater is worse than that in distilled water. In steady condition, the translaminar fracture toughness increases after 7 days immersion and then tends to decrease beyond that immersion time. While in fluctuating condition, the translaminar fracture toughness increases until 15 days immersion and then gradually decreases up to 30 days immersion. Overall, the degradation of mechanical properties in the fluctuating condition is lower than in the steady condition.     

Mechanical characterisation and impact behaviour of concrete reinforced with natural fibres

It is well known that high strength concrete displays a brittle behaviour and less tough characteristics than normal strength concrete. This type of behaviour can be enhanced by incorporating various types of fibres which lead to better mechanical properties and impact resistance. In this paper, an experimental study conducted on high strength concrete reinforced with glass fibres and natural fibres (palm tree leaves), both used at a relatively low volume fraction, is presented. Compressive, splitting, three-point bending and impact test methods have been used to characterise reinforced concrete materials, and the results are analysed statistically. It is observed that natural fibres enhanced the mechanical properties and impact resistance of concrete and exhibit comparable response to the glass fibres. A finite element model using ANSYS was employed to study the flexural behaviour of fibre reinforced concrete. It is concluded that both experimental and numerical results are in good agreement.     

Influence of silane coupling agents on interlaminar fracture in glass fibre fabric reinforced unsaturated polyester laminates

The relationship between the adhesive properties of the interphase of glass fibre/resin and the resultant composite Mode I delamination fracture toughness in glass fibre fabric laminate (GFFL) was studied. The Mode I interlaminar fracture toughness of GFFL was obtained by using a double cantilever beam (DCB) specimen. The delamination resistance of GFFLs which have two silane coupling agents and three concentration finishes is discussed on the basis of interlaminar fracture toughness. The crack propagation behaviour of DCB testing was mainly divided into stable and unstable manners. The fracture toughness and the crack propagation behaviour were dependent on the types and concentration of silane coupling agents.     

Effect of water absorption on the mechanical properties of hemp fibre reinforced unsaturated polyester composites

Hemp fibre reinforced unsaturated polyester composites (HFRUPE) were subjected to water immersion tests in order to study the effects of water absorption on the mechanical properties. HFRUPE composites specimens containing 0, 0.10, 0.15, 0.21 and 0.26 fibre volume fraction were prepared. Water absorption tests were conducted by immersing specimens in a de-ionised water bath at 25 °C and 100 °C for different time durations. The tensile and flexural properties of water immersed specimens subjected to both aging conditions were evaluated and compared alongside dry composite specimens. The percentage of moisture uptake increased as the fibre volume fraction increased due to the high cellulose content. The tensile and flexural properties of HFRUPE specimens were found to decrease with increase in percentage moisture uptake. Moisture induced degradation of composite samples was significant at elevated temperature. The water absorption pattern of these composites at room temperature was found to follow Fickian behaviour, whereas at elevated temperatures it exhibited non-Fickian.     

KH560功能化氧化石墨烯/光敏性不饱和聚酯树脂复合材料的制备与性能

合成了γ-缩水甘油醚氧丙基三甲氧基硅烷（KH560）功能化氧化石墨烯（FGO）,通过红外光谱和热重进行了表征分析。通过加入FGO对混杂型（自由基-阳离子混杂机制）光敏树脂（CRCPR）进行改性,探讨了FGO的加入对CRCPR的黏度、凝胶率和体积收缩率的影响,并测试了固化FGO/CRCPR复合材料的力学性能。结果表明：与氧化石墨烯（GO）相比,由于功能团的引入,FGO在树脂中呈现良好的分散性,少量FGO的引入既未明显改变树脂的黏度,也未降低树脂的凝胶率;同时,极少量FGO的加入即可大幅提高固化FGO/CRCPR复合材料的力学性能,当FGO的质量分数为0.06%时,体积收缩率降低了37%,拉伸强度和弯曲强度分别提高了71.8%和26.9%,冲击强度也提高了49.7%。良好的力学性能与FGO良好分散性及FGO与CRCPR基体良好的界面性能有关。