The effect of polypropylene,polyvinyl-alcohol,carbon and glass fibres on geopolymers properties

Recently, the inclusion of different types of fibres into geopolymers, as reinforcement, has amplified due to the rapid increase in geopolymers developments. In spite of geopolymers have prospective properties such as low carbon footprint, low consumption of energy, good compressive strength, resistance to fire, resistance to flame, resistance to corrosion and good durability, they undergo from low tensile strength and flexural strength. To avoid these shortages, different types of fibres could be incorporated into geopolymers to enhance their toughness, tensile strength and ductility. The current survey aims to review the effect of different types of fibres named polypropylene (PP), polyvinyl alcohol (PVA), carbon and glass fibres on the fresh and hardened properties of geopolymers.     

Comparative study of strain rate effects on mechanical properties of glass fibre-reinforced thermoset matrix composite

The tensile dynamic behaviour of glass fibre-reinforced phenolic and polyester resins has been determined in order to find the influence of strain rate on the mechanical properties of composite materials produced by the resin transfer moulding (RTM) and pultrusion processes. Data and experimental test systems from the literature are analysed. A new specimen design is created and validated using drop-weight dynamic tests. The dynamic elastic modulus and strength tend to increase in an important ratio for the majority of the materials studied. The shear modulus measured with off-axis and ±45° coupons produces different effects as a function of strain rate. The influence of the reinforcement structure is emphasized and shown to be effective.     

Regenerating the strength of thermally recycled glass fibres using hot sodium hydroxide

Results are presented from the ReCoVeR project on the regeneration of the strength of thermally conditioned glass fibres. Thermal recycling of end-of-life glass fibre reinforced composites or composite manufacturing waste delivers fibres with virtually no residual strength or value. Composites produced from such fibres also have extremely poor mechanical performance. Data is presented showing that a short hot sodium hydroxide solution treatment of such recycled fibres can more than triple their strength and restore their ability to act as an effective reinforcement in second life composite materials. The implications of these results for real materials reuse of recycled glass fibres as replacement for pristine reinforcement fibres are discussed.     

Thermal conductivity and thermal diffusivity analyses of low-density polyethylene composites reinforced with sisal, glass and intimately mixed sisal/glass fibres

The thermal conductivity and thermal diffusivity of sisal-reinforced polyethylene (SRP), glass-reinforced polyethylene (GRP) and sisal/glass hybrid fibre-reinforced polyethylene (GSRP) has been evaluated at cryogenic to high temperature (120–350 K). It has been observed that the variation of thermal conductivity with temperature is almost the same for LDPE and SRP containing perpendicularly oriented sisal fibres. The difference between the values of thermal conductivity shown by LDPE and GRP is greater than that of SRP and LDPE. The enhanced thermal conductivity of glass fibre is due to the presence of Fe²⁺ ions in the glass fibres. The linear variation in thermal conductivity with fibre loading is explained with the help of a model suggested by Agari. The difference between the thermal conductivity properties in directions parallel and perpendicular to the applied flux is a maximum for SRP owing to the anisotropic nature of sisal fibre. The difference is marginal for GRP on account of its isotropic nature. The position of GSRP is found to be intermediate. It can been observed that the variation of thermal diffusivity with temperature is just opposite to that of thermal conductivity. This may be due to a reduction in the mean free path of phonons. An empirical equation is derived to explain the variation in thermal conductivity and thermal diffusivity with temperature.     

Mechanical studies of single glass fibres recycled from hydrolysis process using sub-critical water

The study reports mechanical performance of the recycled glass fibres produced from a water-based solvolysis technology, known as the hydrolysis process. The chemical reaction was carried out using sub-critical water to dissolve polyester resin and recover the glass fibres from composites. The effect of temperatures, times, catalyst and water amount on mechanical properties of the recovered glass fibres were investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and time-of flight secondary ion mass spectroscopy (ToF-SIMS) analyses were also employed to examine the fibre surface associated with the polyester resin eliminated level after the hydrolysis reaction. The results revealed that by carefully adjusting the hydrolysis parameters the tensile strength and failure strain of the recycled fibres decrease by approximately 40-70% in comparison with virgin fibres while Young’s moduli remain similar. The relationship between the hydrolysis conditions, recovered fibres and mechanical performance was discussed in this study.     

The role of a polyamide interphase on carbon fibres reinforcing an epoxy matrix

Carbon fibres were pretreated by means of an interfacial in-situ polyamidation technique resulting in a polyamide coating of the fibres. The procedure followed involved successive application to the carbon fibres of two immiscible solutions of hexamethylenediamine and adipoyl chloride. Previous work conducted in our laboratory on chrysotile/epoxy composites coated with Nylon 6,6 provided interesting results when the tensile performance was evaluated. This behaviour was attributed to the improved affinity between matrix and asbestos fibres as a result of the well-known compatibility between polyamide and the epoxy phase. In this study emphasis is given to the coating of long carbon fibres such as are used for the preparation of unidirectional carbon/epoxy composites. The mechanical properties of uniaxial laminates with varying fibre volume fractions and polyamide contents are then compared with those of uncoated carbon fibres.     

Effect of fibre conditioning on the interfacial shear strength of glass-fibre composites

A study of the interaction of water-sized E glass fibres, supplied with and without an aminopropylsilane coupling agent, with vinyl and epoxy resins is reported. Interfacial shear strength measurements, made by means of the multifragmentation technique, have demonstrated that molecularly thin layers are effective adhesion promoters, as indicated by (a) the silane contamination on the nominally non-coupled fibres and (b) the aqueous extraction of the coupled fibres. Epoxy resins adhere through amino coupling reactions, but for the vinyl ester resin the maximum adhesion probably occurs through aluminium hydroxide sites exposed through extractive hydrolysis, and acidic residues in the resin.     

Terahertz spectroscopy to study the orientation of glass fibres in reinforced plastics

We employ terahertz time-domain spectroscopy (THz TDS), a novel, non-destructive testing method, to study the fibre orientation and fibre content in reinforced plastics. The birefringent properties of plastics filled with differing amounts of short glass fibres are measured at frequencies from 100 GHz up to 1 THz. To predict the permittivity of the experimentally examined composite materials, we use an effective medium theory first introduced by Polder and van Santen. On the basis of the measured data and this model, we deduce the additive content ξ, the preferential orientation of the fibres φ and the fraction of orientated fibres a. Our findings agree well with corresponding mold flow simulations performed with commercially available software.     

Effect of fibre volume fraction on fatigue behaviour of glass fibre reinforced composite

The aim of this paper is to study the fatigue behavior of GFRP composites manufactured by vacuum bagging process by varying the volume fraction. Constant‐amplitude flexural fatigue tests were performed at zero mean stress, i.e. a cyclic stress ratio R=?1 by varying the frequency of the testing machine. The relationship between stiffness degradation rate and fibre volume fraction, was observed, and the influence of volume fraction on the tensile strength was also investigated. The results show that, as the volume fraction increases the stiffness degradation rate initially decreases and then increases after reaching a certain limit for the volume fraction. Graph between volume fraction and Young's modulus shows that as the volume fraction increases Young's modulus also increases and reaches a limit and then it decreases with further increase in volume fraction, due to the increase in fibre content which changes the material properties of the composite material. The obtained results are in agreement with the available results.     

SWNT composite coatings as a strain sensor on glass fibres in model epoxy composites

The preparation of a model glass-fibre/epoxy composite with single-walled carbon nanotubes (SWNTs) incorporated as a strain sensor on the fibre surface is described. A micromechanical study of stress transfer at the fibre–matrix interface followed using Raman spectroscopy properties is reported. The SWNTs were distributed along the fibre surface either by dispersing them in an amino-silane coupling agent or coating with an epoxy resin solution containing the SWNTs. The point-by-point mapping of the fibre strain in single fibre fragmentation tests has been undertaken for the first time using SWNTs on the fibres and the interfacial shear stress distribution along the fibre length was determined using the embedded SWNTs. The behaviour was found to be consistent with the classical shear-lag model. The effects of SWNT type and preparation procedure on the sensitivity of the technique were evaluated and optimized from single fibre deformation tests.     

槽沉法制备长余辉发光玻璃微球

选择铝硼硅酸盐玻璃体系，高温熔融法制备了Eu，Dy掺杂的铝硼酸盐基质透明玻璃，并采用槽沉法制备了透明玻璃微球．利用XRD、SEM和荧光光谱对样品进行分析．结果表明：该玻璃微球粒径分布范围窄，光学性能好，其折射率为1．690；单掺杂和双掺杂玻璃微球均具有长余辉发光性能，单掺杂Eu^2＋发光峰位于460nm，而双掺杂Eu^2＋、Dy^3＋的发光峰分别位于456和452nm，并且样品的发光时间达到15h以上。     

Visualization of debonding of fully and partially embedded glass fibres in epoxy resins

Very short glass fibres have been embedded in bars of epoxy resin and the debonding process was observed under the microscope as the polymer was stressed. In addition, fibre pull-out specimens have been similarly watched while the fibre was pulled. The interfaces of the fully embedded fibres failed across the fibre ends at strains of 0·2–0·3%, and circumferential failure started at about 0·6% strain. The low values for the end failures are compatible with models involving stress concentrations at the fibre ends. The circumferential failure value is in agreement with the results of earlier pull-out studies. In the case of the pull-out specimen, the behaviour was complex. Fibres with short embedded lengths debonded first across the embedded end. Failure of the cylindrical surface was too fast for the direction of crack propagation to be determined. Longer fibres first debonded at the fibre entry point and then arrested while debonding occurred across the embedded end. Final failure was again very fast. Long fibres debonded continuously, starting at the entry point. A slow fracture process appeared to be involved at least initially, so that the average shear stress on the region still bonded increased continuously throughout the process. Fast fracture occurred only in the very last stages of the process. These observations are compatible with the traditional theory, but reverse bonding is not ruled out for the shortest embedded lengths.     

Optimum stacking sequence design of laminated composite circular plates with curvilinear fibres by a layer-wise optimization method

The optimum stacking sequence design for the maximum fundamental frequency of symmetrically laminated composite circular plates with curvilinear fibres is investigated for the first time using a layer-wise optimization method. The design variables are two fibre orientation angles per layer. The fibre paths are constructed using the method of shifted paths. The first-order shear deformation plate theory and a curved square p-element are used to calculate the objective function. The blending function method is used to model accurately the geometry of the circular plate. The equations of motion are derived using Lagrange’s method. The numerical results are validated by means of a convergence test and comparison with published values for symmetrically laminated composite circular plates with rectilinear fibres. The material parameters, boundary conditions, number of layers and thickness are shown to influence the optimum solutions to different extents. The results should serve as a benchmark for optimum stacking sequences of symmetrically laminated composite circular plates with curvilinear fibres.     

CBR strength of reinforced soil with natural fibres and considering environmental conditions

This paper investigates the effect of including randomly spaced palm fibres in a soil matrix. The fibres in date palm have special properties such as low costs, plenitude in the region, durability, lightweight, high tension capacity and relative strength against deterioration. Thus, it is possible to use the palm fibres as an alternative low-cost natural material for soil reinforcement. As the objective of this research was to mix the soil and date palm fibres to use in the construction of soil roads, especially village road, we discuss the influence of date palm fibres on CBR (California Bearing Ratio) strength of fine sand. CBR tests were conducted under dry and submerged conditions. The durability of fibres was also investigated using the plain fibres and fibres coated with bitumen. Some samples were soaked for several months before being loaded. The results show that the addition of palm fibres increases the CBR strength of the sand specimens significantly. It is also seen that the sliding strength controls the failure of the specimens rather than the rupture strength.     

In vitro evaluation of borate-based bioactive glass scaffolds prepared by a polymer foam replication method

Borate-based bioactive glass scaffolds with a microstructure similar to that of human trabecular bone were prepared using a polymer foam replication method, and evaluated in vitro for potential bone repair applications. The scaffolds (porosity = 72 ± 3%; pore size = 250–500 μm) had a compressive strength of 6.4 ± 1.0 MPa. The bioactivity of the scaffolds was confirmed by the formation of a hydroxyapatite (HA) layer on the surface of the glass within 7 days in 0.02 M K₂HPO₄ solution at 37 °C. The biocompatibility of the scaffolds was assessed from the response of cells to extracts of the dissolution products of the scaffolds, using assays of MTT hydrolysis, cell viability, and alkaline phosphatase activity. For boron concentrations below a threshold value (0.65 mM), extracts of the glass dissolution products supported the proliferation of bone marrow stromal cells, as well as the proliferation and function of murine MLO-A5 cells, an osteogenic cell line. Scanning electron microscopy showed attachment and continuous increase in the density of MLO-A5 cells cultured on the surface of the glass scaffolds. The results indicate that borate-based bioactive glass could be a potential scaffold material for bone tissue engineering provided that the boron released from the glass could be controlled below a threshold value.     

盐雾环境对玻璃纤维增强树脂基复合材料力学性能的影响

采用中性盐雾条件模拟海洋大气环境进行加速老化试验, 评价玻璃纤维增强环氧改性酚醛树脂基复合材料( GFRP) 在海洋气候中的耐久性。通过该复合材料经盐雾老化后的质量变化和纵向拉伸强度、横向拉伸强度、压缩强度、层间剪切强度的变化, 结合湿热老化机理, 研究其老化规律。结果表明, 随着老化时间的增加, 复合材料的吸湿量增加, 力学强度下降, 压缩和层间剪切曲线表现出塑性特征。吸湿最初阶段对力学性能影响最大, 纵向拉伸强度、横向拉伸强度、压缩强度、层间剪切强度分别下降到56. 1 %、54. 7 %、54. 0 %、61. 0 %。其中拉伸强度变化趋势最稳定, 更适用于评价该复合材料的老化程度。      

Novel method for improving fatigue behaviour of laminated glass

Fatigue‐prone structures made of the laminated glass (LG) are yet not given the due consideration by the scientific community. In this work, a novel method that increases the fatigue life and improves the post breakage performance of the LG structure (by modifying the fracture pattern) is reported in the present work. The fatigue life of LG samples (having PVB interlayer of 0.76‐mm thickness) is evaluated using the standard method. Further, a theoretical explanation is presented for improved fatigue behaviour of LG. The effect of treatment of LG and cyclic bending fatigue load on cyclic fatigue strength is reported. The cyclic fatigue strength of LG increases 19.1% to 30.5% for treated LG samples when compared to untreated samples. The finite element model is developed (for treated and untreated LG) using the transient analysis in ANSYS 14.5 (Explicit Dynamics Module) to obtain the maximum deformation at failure load for the corresponding number of cycles. The strain‐life relations are established. The previously established fracture models and underdeveloped nanofracture mechanics concepts are used to explain the fracture patterns of the LG samples. Analysis of variance is conducted to ensure the validity of the experimental results.     

喷镀法制备SnO2膜导电玻璃的研究

用喷镀法将 Sn Cl4溶液喷射到预先加热的玻璃表面 ,制成了薄膜电阻 <70 Ω/□ ,透光率 >88% ,热稳定性 <45 %的 Sn O2 膜导电玻璃 ,研究了膜厚、基底温度、溶液组成对薄膜电阻与透光率的影响。     

风力发电机叶片用玻璃纤维织物的渗透率

通过改变纤维层数来改变纤维织物的孔隙率,采用一维饱和流动方法测量了风力发电叶片用玻璃纤维织物(WindstrandTM)三个方向(x、y和z)的饱和渗透率大小.考察了孔隙率、模具尺寸以及纤维方向(平行于和垂直于2％的纤维束两个方向)对其饱和渗透率的影响.结果表明:渗透率随孔隙率的降低而迅速降低；当孔隙率为34.6％～54.7％时,模具尺寸对y向饱和渗透率影响不大；改变2％的纤维束方向(由平行到垂直),当孔隙率为34.6％～54.7％时,对饱和渗透率有一定影响.当孔隙率为45％～55％时,玻璃纤维织物x和y方向的饱和渗透率约为z方向饱和渗透率的3～7倍.     

Impact and post-impact damage characterisation of hybrid composite laminates based on basalt fibres in combination with flax,hemp and glass fibres manufactured by vacuum infusion

The impact and flexural post-impact behaviour of ternary hybrid composites based on epoxy resin reinforced with different types of fibres, basalt (B), flax (F), hemp (H) and glass (G) in textile form, namely FHB, GHB and GFB, has been investigated. The reinforcement volume employed was in the order of 21–23% throughout. Laminates based exclusively on basalt, hemp and flax fibres were also fabricated for comparison. Hybrid laminates showed an intermediate performance between basalt fibre reinforced laminates on the high side, and flax and hemp fibre reinforced laminates on the low side. As for impact performance, GHB appears to be the worst performing hybrid laminate and FHB slightly overperforms GFB. In general, an increased rigidity can be attributed to all hybrids with respect to flax and hemp fibre composites. The morphological study of fracture by SEM indicated the variability of mode of fracture of flax and hemp fibre laminates and of the hybrid configuration (FHB) containing both of them. Acoustic emission monitoring during post-impact flexural tests confirmed the proneness to delamination of FHB hybrids, whilst they were able to better withstand impact damage than the other hybrids.