Improved tensile properties of basalt fibre reinforced polymer composites using silica nanoparticles

In this study, the effect of silica nanoparticles as the reinforcing filler on the tensile response of basalt fibre reinforced polymer (BFRP) composite was investigated. A 40 wt.% nanosilica gel in epoxy was used to prepare a series of nanocomposites with 5 wt.%, 15 wt.% and 25 wt.% nanosilica. Static uniaxial tensile tests were conducted on the basalt fibre reinforced polymer composite to investigate the stress‐strain response of the unmodified and nanomodified composites. It was found that the incorporation of silica nanoparticles with high specific surface area improved the tensile properties of the basalt fibre reinforced polymer composite. The addition of silica nanoparticles in the composite shows significant improvement in tensile modulus with 6 %, 14 % and 19 % for 5 wt.%, 15 wt.% and 25 wt.% nanosilica content, respectively. The higher content of silica nanoparticles in the matrix increased the stiffness of the material as well as the strength of the basalt fibre reinforced polymer composite without reducing the failure strain.     

Fracture characterisation of short bamboo fibre reinforced polyester composites

In the study, fracture behaviour of short bamboo fibre reinforced polyester composites is investigated. The matrix is reinforced with fibres ranging from 10 to 50, 30 to 50 and 30 to 60 vol.% at increments of 10 vol.% for bamboo fibres at 4, 7 and 10 mm lengths respectively. The results reveal that at 4 mm of fibre length, the increment in fibre content deteriorates the fracture toughness. As for 7 and 10 mm fibre lengths, positive effect of fibre reinforcement is observed. The optimum fibre content is found to be at 40 vol.% for 7 mm fibre and 50 vol.% for 10 mm fibre. The highest fracture toughness is achieved at 10 mm/50 vol.% fibre reinforced composite, with 340% of improvement compared to neat polyester. Fractured surfaces investigated through the Scanning Electron Microscopy (SEM) describing different failure mechanisms are also reported.     

A review on basalt fibre and its composites

In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as polymer (both thermoplastic and thermoset), metal and concrete has been presented. Furthermore, an overview on the application of this fibre in biodegradable matrix composites and in hybrid composites has been provided. Finally, the studies on the industrial applications of basalt fibre reinforced composites have been reviewed.     

Effects of static–fatigue (tension) on the tension–tension fatigue life of glass fibre reinforced plastic composites

The effects of static–fatigue interaction on tension–tension fatigue life of glass fibre reinforced plastic (GFRP) composites were investigated. This paper proposed a new static–fatigue model, which is capable of predicting residual strength after a period of static loading. Also an algorithm is proposed to calculate fatigue lives with the inclusion of static–fatigue interaction. Predictions from the proposed static–fatigue model show a good agreement with the experimental results. Static–fatigue interaction has shown a considerable effect on fatigue lives of GFRP composites at intermediate and lower applied stress levels possibly due to a longer exposure to applied loads. At higher load levels approximately greater than 65% of ultimate stress, and higher stress ratios range like 0.5 < R < 0.9, fatigue lives shown to be closer to material’s static–fatigue limits which is shorter than the expected lifetime by cyclic fatigue.     

Impact and fatigue behaviour of hemp fibre composites

A series of experiments has been carried out to characterize the residual tensile and fatigue properties following impact of non-woven hemp fibre mat reinforced polyester. Additionally, the degradation of tensile modulus during fatigue cycling has been studied and related to the damage accumulation. For comparison purposes, ±45° glass fibre reinforced polyester samples have also been subjected to similar tests. It was found necessary to apply a relatively high pressure to the hemp composite during the curing stage in order to ensure a high enough fibre fraction to provide a significant reinforcing effect. With similar fibre weight fractions, the hemp and glass reinforced materials exhibited similar static tensile properties and fatigue lifetimes. Although the slightly steeper S–N curve of the hemp based material indicated a higher rate of reduction in fatigue strength with increasing cycles, it remained above the S–N curve for the glass based material showing that it was able to withstand slightly higher cyclic stress levels for equivalent numbers of cycles. The major difference in mechanical performance was the poorer resistance of the hemp based composite to impact. Also, the hemp based material failed in a much more brittle manner, without any visible signs of damage, such as the matrix cracking that was seen in the glass fibre based composite. It was found that, if the fatigue lifetime data of impact damaged samples were normalized against the post-impact residual tensile strength, then all data points lay close to a common S–N curve. This implies that residual fatigue lifetimes of damaged samples could be predicted from knowledge of their residual strength and the S–N curve for undamaged material.     

Computational fatigue life prediction of continuously fibre reinforced multiaxial composites

The potential of a fatigue-life prediction method for continuously fibre reinforced carbon/epoxy laminates has been investigated. Stress analysis conducted with a finite element solver in combination with the experimentally measured anisotropic S–N curves was used as input parameters. Subsequently, lifetime of a unidirectional and a multidirectional composite was calculated for a cyclic tension–tension load case and validated with experimental fatigue tests. The predicted lifetime of the unidirectional laminate correlated well to the experimental results. For the fatigue-life calculation of multidirectional composites, the software underestimated the experimental data. Results and possible improvements based on the presented calculations are discussed in detail.     

Fatigue behavior and failure mechanism of basalt FRP composites under long-term cyclic loads

This paper studies the fatigue behavior of basalt fiber reinforced epoxy polymer (BFRP) composites and reveals the degradation mechanism of BFRP under different stress levels of cyclic loadings. The BFRP composites were tested under tension–tension fatigue load with different stress levels by an advanced fatigue loading equipment combined with in-situ scanning electron microscopy (SEM). The specimens were under long-term cyclic loads up to 1 × 10⁷ cycles. The stiffness degradation, S–N curves and the residual strength of run-out specimens were recorded during the test. The fatigue strength was predicted with the testing results using reliability methods. Meanwhile, the damage propagation and fracture surface of all specimens were observed and tracked during fatigue loading by an in-situ SEM, based on which damage mechanism under different stress levels was studied. The results show the prediction of fatigue strength by fitting S–N data up to 2 × 10⁶ cycles is lower than that of the data by 1 × 10⁷ cycles. It reveals the fatigue strength perdition is highly associated with the long-term run-out cycles and traditional two million run-out cycles cannot accurately predict fatigue behavior. The SEM images reveal that under high level of stress, the critical fiber breaking failure is the dominant damage, while the matrix cracking and interfacial debonding are main damage patterns at the low and middle fatigue stress level for BFRP. Based on the above fatigue behavior and damage pattern, a three stage fracture mechanism model under fatigue loading is developed.     

Behaviour ofE-glass fibre reinforced vinylester resin composites under impact fatigue

An impact fatigue study has been made for the first time on 63.5% glass fibre reinforced vinylester resin notched composites. The study was conducted in a pendulum type repeated impact apparatus especially designed and fabricated for determining single and repeated impact strengths. A well-defined impact fatigue (S-N) behaviour, having a progressive endurance below the threshold single cycle impact fracture stress with decreasing applied stress has been demonstrated. Fractographic analysis revealed fracture by primary debonding having fibre breakage and pullout at the tensile zone, but a shear fracture of fibre bundles at the compressive zone of the specimen. The residual strength, modulus and toughness showed retention of the properties at high impact stress levels up to 1000 impacts followed by a sharp drop. Cumulative residual stresses with each number of impacts not withstanding the static fatigue failure at long endurances have been ascribed for the composite failures under the repeated impact stresses.     

Fire structural resistance of basalt fibre composite

Basalt fibres are emerging as a replacement to E-glass fibres in polymer matrix composites for selected applications. In this study, the fire structural resistance of a basalt fibre composite is determined experimentally and analytically, and it is compared against an equivalent laminate reinforced with E-glass fibres. When exposed to the same radiant heat flux, the basalt fibre composite heated up more rapidly and reached higher temperatures than the glass fibre laminate due to its higher thermal emissivity. The tensile structural survivability of the basalt fibre composite was inferior to the glass fibre laminate when exposed to the same radiant heat flux. Tensile softening of both materials occurred by thermal softening and decomposition of the polymer matrix and weakening of the fibre reinforcement, which occur at similar rates. The inferior fire resistance of the basalt fibre composite is due mainly to higher emissivity, which causes it to become hotter in fire.     

Material instability in fatigue of fibre composites

Research of the ultimate behaviour of the carbon fibre composites is treated in the present paper. The material instability on the basis of the fibre kinking theory is adopted for the treatment of the failure process in the problem. The micromechanical modelling adopting the FETM‐wave approach is used for the numerical analysis of the problem. Some numerical and experimental results obtained are submitted in order to demonstrate the efficiency of the procedures suggested. Copyright © 2004 John Wiley & Sons, Ltd.     

纤维增强聚合物基复合材料的低温性能

对纤维增强聚合物基复合材料在低温领域的实际应用进行了分类介绍,通过对纤维增强聚合物基复合材料的低温性能、性能影响因素和作用机理、低温应用安全性等方面的研究工作进行总结,突出各类纤维增强聚合物基复合材料低温下的性能优势,阐明了材料性能的不足之处及相应改进措施.对于实际低温应用中纤维增强聚合物基复合材料的选择、性能设计优化,系统安全性的增强提供了参考作用.     

Influence of basalt fibres on free and restrained plastic shrinkage

Early-age cracking due to plastic shrinkage is often attributed to reducing the durability of concrete structures. The objective of this paper is to evaluate the potential use of chopped basalt fibres in preventing these cracks. Testing was undertaken to measure the magnitude of shrinkage strain that develops in unrestrained specimens, and the severity of cracking that occurs when shrinkage is restrained. Results indicate basalt fibres are effective in preventing cracks by reducing the magnitude of free shrinkage, and by restricting the growth of cracks if they do occur. The latter mechanism is more prominent when the w/c ratio is decreased.     

Finite–element analysis of selectively SiC fibre–reinforced titanium composites (II)

Finite-element analysis has been carried out to predict the through-thickness stresses generated at the transition boundary between monolithic cladding layers and SiC fibre reinforced titanium matrix composite plates. Such stresses have been shown in studies elsewhere to promote premature transverse damage near the transition region ahead of a mode I crack propagating within the cladding layer. Results obtained in DEN tension are presented to demonstrate the influence of thermal residual stress, external loading, and the relative thicknesses of the cladding material and the composite regions, on the through-thickness stresses. A dimensionless parameter S has been constructed and is demonstrated to provide a useful tool for predicting the potential for through-thickness damage in a range of testpiece dimensions and levels of selective reinforcement. This revised version was published online in August 2006 with corrections to the Cover Date.     

A short review on basalt fiber reinforced polymer composites

A recent increase in the use of ecofriendly, natural fibers as reinforcement for the fabrication of lightweight, low cost polymer composites can be seen globally. One such material of interest currently being extensively used is basalt fiber, which is cost-effective and offers exceptional properties over glass fibers. The prominent advantages of these composites include high specific mechano-physico-chemical properties, biodegradability, and non-abrasive qualities to name a few. This article presents a short review on basalt fibers used as a reinforcement material for composites and discusses them as an alternative to the use of glass fibers. The paper also discusses the basics of basalt chemistry and its classification. Apart from this, an attempt to showcase the increasing trend in research publications and activity in the area of basalt fibers is also covered. Further sections discuss the improvement in mechanical, thermal and chemical resistant properties achieved for applications in specific industries.     

Multiaxial fatigue of a short glass fibre reinforced polyamide 6.6 – Fatigue and fracture behaviour

The multiaxial fatigue behaviour of a short glass fibre reinforced polyamide 6.6 (PA66-GF35) is investigated on hollow tubular specimens in the range of fatigue lives between 10² and 10⁷ cycles. Fatigue experiments included pure tension, pure torsion, combined tension–torsion at different biaxiality ratios and phase shifting angles between the stress components. Tests were carried out with load ratio R = 0 and R = −1 at room temperature as well as at 130 °C. The influence of biaxiality ratio, phase angle between load components and load ratio is discussed.An extensive analysis of the fracture behaviour is performed on the specimens to recognise the crack nucleation and propagation mechanisms; failure modes were evaluated via optical and scanning electron microscopy.     

Influence of low velocity impact on fatigue behaviour of woven hemp fibre reinforced epoxy composites

The purpose of this work is to study the resistance to low velocity impact of woven hemp/epoxy matrix composites and the influence of impact damage on their residual quasi-static tensile and cyclic fatigue strengths. Impact characteristic parameters were evaluated and critically compared to those found in the literature for other similar composites. Damage mechanisms were analysed by using AE monitoring and microscopic observations. An analytical model is used to predict the fatigue lifetime of impacted specimens. Moreover a damage scenario is proposed, reduced to two phases in post-impacted fatigue behaviour, instead of three phases for non impacted specimens.     

Experimental characterisation of fatigue damage in single Z-pins

Z-pins have been shown to significantly improve delamination resistance and impact strength of carbon fibre reinforced (CFRP) composites. In this paper, an experimental investigation of the influence of different fatigue parameters (mean opening/sliding displacement, amplitude, frequency, number of cycles) on the through-thickness reinforcement (TTR) is presented. For mode I, it is shown that the degradation on pin behaviour during fatigue is mostly affected by the applied displacement amplitude. The degradation is primarily caused by surface wear. Due to the brittleness of the Z-pins, mode II fatigue does not have a significant effect for very small sliding displacements. Exceeding a critical displacement causes the pin to rupture within the very first cycles.     

Effect of basalt fibre hybridisation on post-impact mechanical behaviour of hemp fibre reinforced composites

A major limitation to the spreading of natural fibre reinforced composites in semi-structural components is their unsatisfactory impact performance. As a potential solution, the production of synthetic/plant fibre hybrid laminates has been explored, trying to obtain materials with sufficient impact properties, while retaining a reduced cost and a substantial environmental gain. This study explores the effects of hybridisation of basalt fibre on post-impact behaviour and damage tolerance capability of hemp fibre reinforced composites. All reinforced laminates were impacted in a range of energies (3, 6, and 9 J) and subjected to both quasi-static and cyclic flexural tests with a step loading procedure. The tests have also been monitored by acoustic emission (AE), which has confirmed the existence of severe limitations to the use of natural fibre reinforced composites even when impacted at energies not so close to penetration and the enhanced damage tolerance offered by the hybridisation with basalt fibers.