PSI - Issue 26

Costanzo Bellini et al. / Procedia Structural Integrity 26 (2020) 120–128 Bellini et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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As found for the other laminates, the long beam specimen failure was due to tensile failure of the composite material, as visible in Fig. 9a, even if delamination can be observed. As concerns the interface between the composite and the aluminium, it can be noted that the delamination took place in the composite layer, since a thin deposit of resin is bonded to the aluminium sheet, as visible in Fig. 9b.

4. Conclusion

In the present work, the flexural behaviour of both long and short beam specimens made of CARALL (Carbon Fibre Reinforced Aluminium Laminate) was investigated. This is a hybrid material composed by aluminium sheets alternated to carbon fibre composite layers. Moreover, the influence of both the composite/metal interface and the number of the layers, that was connected to their thickness, were analysed. For this aim, different FMLs made of aluminium and CFRP (Carbon Fibre Reinforced Polymer) were produced varying the thickness and the number of the layers and the adhesion solutions between the constituent materials, considering a structural adhesive or the prepreg resin for the bonding. It was found that the structural adhesive was deleterious for the flexural strength of the long beam, while it improved the behaviour of the short one. This fact was due to the different stress state developing inside the beams: in the former one tensile stress was predominant, so the fibre volumetric content was the most influencing factor, and the presence of the adhesive tended to lower the fibre quantity. On the contrary, in the latter one, the interlaminar shear stresses prevailed, so the interface quality resulted to be important and, consequently, the presence of the adhesive improved the mechanical behaviour. As concerns the thickness and the distribution of the layers, this factor was unaffecting for the short beam specimen, while it was decisive for the long beam one. In fact, considering the abovementioned stress configuration for the different specimens, a higher quantity of composite material in the outer part of the FLM was desirable to withstand the tensile stress. The abovementioned findings were confirmed by the micrographic analysis carried out on the tested specimens, in order to characterize the failure mode. It was found a preponderance of fibre breakage in the long beam, while in the short one the failure of the metal/composite interface was prevailing. Bellini, C., Di Cocco, V., Iacoviello, F., Sorrentino, L., 2019. Performance evaluation of CFRP/Al fibre metal laminates with different structural characteristics. Composite Structures 225, 111117. doi: 10.1016/j.compstruct.2019.111117. Bellini, C., Di Cocco, V., Iacoviello, F., Sorrentino, L., 2019. Experimental Analysis of Aluminium Carbon/Epoxy Hybrid Laminates under Flexural Load. Frattura ed Integrità Strutturale, 49, 739– 747. doi: 10.3221/IGF-ESIS.49.66. Bellini, C., Di Cocco, V., Sorrentino, L., (2020). Interlaminar shear strength study on CFRP/Al hybrid laminates with different properties. Frattura ed Integrità Strutturale 51, 442– 448. doi:10.3221/IGF-ESIS.51.32. Dhaliwal, G.S., Newaz, G.M., 2016. Experimental and Numerical Investigation of Flexural Behavior of Carbon Fiber Reinforced Aluminum Laminates. Journal of Reinforced Plastic Composites 35, 945 – 956. doi:10.1177/0731684416632606. Hamill, L., Hofmann, D.C., Nutt, S., 2018. Galvanic Corrosion and Mechanical Behavior of Fiber Metal Laminates of Metallic Glass and Carbon Fiber Composites. Advanced Engineering Materials 20, 1 – 8. doi:10.1002/adem.201700711. Hu, Y.B., Li, H.G., Cai, L., Zhu, J.P., Pan, L., Xu, J., Tao, J., 2015. Preparation and Properties of Fibre-Metal Laminates Based on Carbon Fibre Reinforced PMR Polyimide. Composites Part B: Engineering 69, 587 – 591. doi:10.1016/j.compositesb.2014.11.011. Jakubczak, P., Bienias, J., Surowska, B., 2018. Interlaminar shear strength of fibre metal laminates after thermal cycles. Composites Structures 206, 876 – 887. doi: 10.1016/j.compstruct.2018.09.001. Lawcock, G.D., Ye, L., Mai, Y.W., Sun, C.T., 1998. Effects of fibre/matrix adhesion on carbon-fibre-reinforced metal laminates - I. residual strength. Composites Science and Technology 57, 1609 – 1619. doi: 10.1016/S0266-3538(97)00108-5. Li, H., Hu, Y., Xu, Y., Zheng, X., Liu, H., Tao, J., 2015. Reinforcement Effects of Aluminumelithium Alloy on the Mechanical Properties of Novel Fiber Metal Laminate, Composites Part B: Engineering 82, 72 – 77. doi:10.1016/j.compositesb.2015.08.013. Li, H., Hu, Y., Fu, X., Zheng, X., Liu, H., Tao, J., 2016. Effect of Adhesive Quantity on Failure Behavior and Mechanical Properties of Fiber Metal Laminates Based on the Aluminum-Lithium Alloy. Composite Structures 152, 687 – 692. doi:10.1016/j.compstruct.2016.05.098. Mamalis, D., Obande, W., Koutsos, V., Blackford, J.R., Ó Brádaigh, C.M., Ray, D., 2019. Novel thermoplastic fibre -metal laminates manufactured by vacuum resin infusion: The effect of surface treatments on interfacial bonding. Materials and Design 162, 331 – 344. doi: 10.1016/j.matdes.2018.11.048. Ning, H., Li, Y., Hu, N., Arai, M., Takizawa, N., Liu, Y., Wu, L., Li, J., Mo, F., 2015. Experimental and Numerical Study on the Improvement of Interlaminar Mechanical Properties of Al/CFRP Laminates. Journal of Materials Processing Technology 216, 79 – 88. doi:10.1016/j.jmatprotec.2014.08.031. References