Materials and Design 54(2014)893-899 Contents lists available at ScienceDirect Materials and design ELSEVIER journalhomepagewww.elsevier.com/locate/matdes Flexural and tensile moduli of unidirectional hybrid epoxy composites () cosMark reinforced by s-2 glass and T700S carbon fibres Chensong Dong, lan J Davies Department of Mechanical Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia A INFO ABSTRACT A study on the flexural and tensile moduli of S-2 glass and T700S carbon fibre reinforced hybrid epoxy Received 18 April 2013 nent analysis(FEA)ar Accepted 24 August 2013 Lamination Theory(CLt) were employed to model the flexural behaviour of hybrid composites, which line 30 August 201 was obtained from the three point bend test in accordance with ASTM: D790-10 at various span-to-depth ratios. The flexural moduli were obtained from the load-dis rves. Th against the experimental results from a previous study. with the aid of the developed models, the effects of fibre volume fractions, hybrid ratio and span-to-depth ratio were studied. The results show that flex ral modulus increases when the span-to-depth ratio is increased from 16 to 32 and becomes stable as ne span-to-depth ratio further increases. Since the modulus of glass fibres is much lower than that of exural modulus arbon fibres, both flexural and tensile moduli decrease with increasing hybrid ratio From the full car Tensile modulus bon/epoxy laminate, when a carbon/epoxy lamina close to the outermost surface of the laminate is eplaced by a glass/epoxy lamina, the flexural modulus decreases rapidly. This is due to the maximum ensile and compressive stresses occur at the two faces of the laminate in bending, and the stresses round the mid-plane are close to zero Tensile modulus decreases with increasing hybrid ratio Under nsion, the stress distribution is determined by the relative difference in the tensile moduli of the car- bon/epoxy and glass/epoxy laminas. If the difference is small, tensile modulus versus the hybrid ratio resembles a linear relationship and no significant hybrid effects exist; if rence is large, a strong non-linear relationship is present and large hybrid effects exist. Simple hemat tical formulas are pre- sented for calculation of the flexural and tensile moduli of hybrid composi the moduli of the car- bon/epoxy and glass/epoxy composites, and the hybrid ratio. o 2013 Elsevier Ltd. All rights reserved. 1 Introduction High elongation fibres enhance the strain levels required to propagate cracks through the composites and hence behave like Many types of fibres, e. g. glass, carbon, have been used to make crack arrestors on a micromechanical level [4]. fibre reinforced polymer composites. Each fibre type has its advan- According to the layup hybrid composites can be categorized tages and disadvantages. If two or more different types of fibres are into intimately mixed, intra-ply, inter-ply and sandwich types 5]. sed to reinforce a polymer, it is possible to obtain a composite A convenient way to estimate the stiffness or strength of a hy- with balanced properties. Such composite is called hybrid brid composite is using the rule of i es(roM)approach from composite. the individual properties and the volume concentration of its con- In a fibre reinforced composite, fibres are the main load carrying stituents. However, it has been found that the rom predictions component. In general, carbon fibres have high strength and stiff- fer to the actual properties. a positive or negative hybrid effect is ness while glass fibres have moderate strength and low stiffness defined as a positive or negative deviation of a certain mechanical [1, 2]. In other words, carbon fibres are low elongation fibres while property from the roM behaviour, respectively [6. glass fibres are high elongation fibres. Thus, it is possible to incor The mechanical properties of glass and carbon fibre reinforced porate glass fibres into carbon fibres to improve the failure strain hybrid epoxy composites have been studied extensively [4,5.7 to modify the failure strain 3. 14. Most studies were focused on the strength,9-14. Fu et al [10 showed that no hybrid effects for the tensile modulus, while a positive hybrid effect for the flexural modulus. Sudarisman and Davies 11 showed no significant effects of hybridisation to the Corresponding author. Tel. +61(8)92669204: fax: +61(8)92662681 flexural modulus of unidirectional glass and carbon reinforced hy- brid epoxy composites. Fu et al. [15 studied the elastic modulus of 069/S- see front matter o 2013 Elsevier Ltd. All rights reserved Lx. doiorg/10. 1016/j mates. 2013.08.086Flexural and tensile moduli of unidirectional hybrid epoxy composites reinforced by S-2 glass and T700S carbon fibres Chensong Dong ⇑ , Ian J. Davies Department of Mechanical Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia article info Article history: Received 18 April 2013 Accepted 24 August 2013 Available online 30 August 2013 Keywords: Polymer–matrix composites Carbon fibre Glass fibre Hybrid Flexural modulus Tensile modulus abstract A study on the flexural and tensile moduli of S-2 glass and T700S carbon fibre reinforced hybrid epoxy composites in intra-ply configurations is presented in this paper. Finite element analysis (FEA) and Classic Lamination Theory (CLT) were employed to model the flexural behaviour of hybrid composites, which was obtained from the three point bend test in accordance with ASTM: D790-10 at various span-to-depth ratios. The flexural moduli were obtained from the load–displacement curves. The models were validated against the experimental results from a previous study. With the aid of the developed models, the effects of fibre volume fractions, hybrid ratio and span-to-depth ratio were studied. The results show that flex￾ural modulus increases when the span-to-depth ratio is increased from 16 to 32 and becomes stable as the span-to-depth ratio further increases. Since the modulus of glass fibres is much lower than that of carbon fibres, both flexural and tensile moduli decrease with increasing hybrid ratio. From the full car￾bon/epoxy laminate, when a carbon/epoxy lamina close to the outermost surface of the laminate is replaced by a glass/epoxy lamina, the flexural modulus decreases rapidly. This is due to the maximum tensile and compressive stresses occur at the two faces of the laminate in bending, and the stresses around the mid-plane are close to zero. Tensile modulus decreases with increasing hybrid ratio. Under tension, the stress distribution is determined by the relative difference in the tensile moduli of the car￾bon/epoxy and glass/epoxy laminas. If the difference is small, tensile modulus versus the hybrid ratio resembles a linear relationship and no significant hybrid effects exist; if the difference is large, a strong non-linear relationship is present and large hybrid effects exist. Simple mathematical formulas are pre￾sented for calculation of the flexural and tensile moduli of hybrid composites from the moduli of the car￾bon/epoxy and glass/epoxy composites, and the hybrid ratio. 2013 Elsevier Ltd. All rights reserved. 1. Introduction Many types of fibres, e.g. glass, carbon, have been used to make fibre reinforced polymer composites. Each fibre type has its advan￾tages and disadvantages. If two or more different types of fibres are used to reinforce a polymer, it is possible to obtain a composite with balanced properties. Such composite is called hybrid composite. In a fibre reinforced composite, fibres are the main load carrying component. In general, carbon fibres have high strength and stiff￾ness while glass fibres have moderate strength and low stiffness [1,2]. In other words, carbon fibres are low elongation fibres while glass fibres are high elongation fibres. Thus, it is possible to incor￾porate glass fibres into carbon fibres to improve the failure strain to modify the failure strain [3]. High elongation fibres enhance the strain levels required to propagate cracks through the composites and hence behave like crack arrestors on a micromechanical level [4]. According to the layup, hybrid composites can be categorized into intimately mixed, intra-ply, inter-ply and sandwich types [5]. A convenient way to estimate the stiffness or strength of a hy￾brid composite is using the rule of mixtures (RoM) approach from the individual properties and the volume concentration of its con￾stituents. However, it has been found that the RoM predictions dif￾fer to the actual properties. A positive or negative hybrid effect is defined as a positive or negative deviation of a certain mechanical property from the RoM behaviour, respectively [6]. The mechanical properties of glass and carbon fibre reinforced hybrid epoxy composites have been studied extensively [4,5,7– 14]. Most studies were focused on the strength [7,9–14]. Fu et al. [10] showed that no hybrid effects for the tensile modulus, while a positive hybrid effect for the flexural modulus. Sudarisman and Davies [11] showed no significant effects of hybridisation to the flexural modulus of unidirectional glass and carbon reinforced hy￾brid epoxy composites. Fu et al. [15] studied the elastic modulus of 0261-3069/$ - see front matter 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.08.086 ⇑ Corresponding author. Tel.: +61 (8) 92669204; fax: +61 (8) 92662681. E-mail address: c.dong@curtin.edu.au (C. Dong). Materials and Design 54 (2014) 893–899 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes