PSI - Issue 28

Haibao Liu et al. / Procedia Structural Integrity 28 (2020) 106–115 Liu H et al./ Structural Integrity Procedia 00 (2020) 000–000

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5. Conclusions A round-nosed steel impactor was employed to impact continuous carbon-fibre reinforced plastic (CFRP) composites at two velocities, i.e. 2.40 m.s -1 (giving an impact energy of 15 J) and 4.16 m.s -1 (giving an impact energy of 45 J), to investigate the effects of the impact velocity and associated energy. Also, a flat-faced steel impactor was used to impact the composites at a velocity level of 2.40 m.s -1 to study the effects of the shape of the head of impactor. All the composite specimens were then inspected using an ultrasonic C-scan test to assess the impact damage. Firstly, it was found that, using the round-nosed steel impactor, the higher impact velocity caused significantly more damage in the composites than the lower velocity impact. Further, when the impact velocity was increased from 2.40 m.s -1 to 4.16 m.s -1 more delamination was observed near the rear surface of the composite, whilst the delamination near the front face did not show a significant difference. Secondly, the composite specimens struck with the flat-faced steel impactor suffered a higher maximum load upon impact, but experienced a smaller out-of-plane displacement, than those struck with the round-nosed steel impactor at the same impact energy of 15 J. A comparison of the experimental C-scan images showed that the delamination maps of the composites impacted with the round-nosed steel and the flat-faced steel impactors were similar in area but with a somewhat larger damage area occurring when the round-nosed steel impactor was used. The composite specimens impacted with the round-nosed steel impactor showed a continuous delamination area, which was centred around the point of impact. In contrast, the flat-ended steel impacted composites exhibited two separate delamination areas, with a central zone exhibiting less delamination. These impact damage processes, for the round-nosed steel and the flat faced steel impactors striking CFRP composites have been modelled using an elastic-plastic 3D stress finite-element analysis (FEA) damage model in Liu et al. (2020a) and using a simpler, but more computationally-efficient, elastic 2D stress FEA damage model, which was developed for the soft impact of composites, in Liu et al. (2020b). Acknowledgements The strong support from the Aviation Industry Corporation of China (AVIC) Manufacturing Technology Institute (MTI) in China, the First Aircraft Institute (FAI) in China and the Aircraft Strength Research Institute (ASRI) in China for this funded research is very much appreciated. Dr Jun Liu appreciates the support and interest in this research by BATRI COMAC (Beijing Aeronautical Technology Research Institute - Commercial Aircraft Corporation of China). The research was performed at the AVIC Centre for Structural Design and Manufacture and the COMAC-Imperial Research Centre for Wing Technology of Commercial Aircraft, at Imperial College London, UK. References ASTM (2014). Standard Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a Drop-Weight Impact Event. D7136/D7136M-05. Borg R, Nilsson L and Simonsson K (2004). Simulation of low velocity impact on fiber laminates using a cohesive zone based delamination model. Compos Sci Technol, 64:279-88. De Freitas MA and Reis L (1998). Failure mechanisms on composite specimens subjected to compression after impact. Compos Struct, 42:365-73. Donadon MV, Iannucci L, Falzon BGG, Hodgkinson JM and De Almeida SF (2008). A progressive failure model for composite laminates subjected to low velocity impact damage. Compos Struct, 86: 1232-52. Elder DJ, Thomson RS, Nguyen MQ, Scott ML (2004). Review of delamination predictive methods for low speed impact of composite laminates. Compos Struct, 66: 677-83. Eyer G, Montagnier O, Hochard C, Charles J (2017). Effect of matrix damage on compressive strength in the fiber direction for laminated composites. Compos Part A Appl Sci Manuf, 94:86-92. González E V., Maimí P, Camanho PP, Turon A and Mayugo JA (2012). Simulation of drop-weight impact and compression after impact tests on composite laminates. Compos Struct, 94:3364-78. Hosseinzadeh R, Shokrieh MM, Lessard L (2006). Damage behavior of fiber reinforced composite plates subjected to drop weight impacts. Compos Sci Technol, 66:61–8. Israr HA, Rivallant S, Bouvet C and Barrau JJ (2014). Finite element simulation of 0/90 CFRP laminated plates subjected to crushing using a free face-crushing concept. Compos Part A Appl Sci Manuf, 62:16-25.