PSI - Issue 53

2

A. Neto et al. / Procedia Structural Integrity 53 (2024) 338–351 Alexandre de Oliveira Neto / Structural Integrity Procedia 00 (2019) 000–000

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Nomenclature CFRP

Carbon Fibre Reinforced Polymer

FEM ASTM

Finite Element Method

American Society for Testing and Materials International Organisation for Standardization Society of Automotive Engineers International American Concrete Institute International American Institute of Aeronautics and Astronautics

ISO

SAE International ACI International

AIAA WWFE

World-Wide Failure Exercise

L1 L2

Layup 1 Layup 2

1. Introduction Composites can take different geometric shapes, depending on what is required. A composite tubular profile is a tubular structure made from composite materials. This type of structure is the result of a natural evolution of planar laminates because, with the advance of technology and the growing need for light and resistant constructions, more complex geometric shapes began to be explored. They can be tubular, square, or rectangular profiles. Their thickness is determined by the loads to be sustained depending on the application. In the automotive industry, they tend to be increasingly common. They are generally found in chassis structures, bodywork, engine parts, and interiors, but more especially in suspension arms, particularly in racing vehicles. The reasons tubular profiles are chosen for these applications are that they are highly resistant to bending, traction and compression, also low in weight and cost-effective: their geometric shape allows loads to be distributed more efficiently. In addition, they are resistant to corrosion and weathering, which makes them ideal for use outdoors. On the one hand, to maximize these advantages, special care must be taken during manufacture and maintenance to ensure safety and structural integrity, notably during the design phase. Despite the recurrent use of CFRP (Carbon fibre reinforced polymer) structures and their many advantages, they can also be very fragile under certain situations, where common damages such as delamination, fibre and/or matrix cracking, can occur especially under impacts. Impacts such as low velocity, which are very common in-service conditions cause consequences that are often overlooked, due to not being visible to the naked eye. To combat that, there is a need to study energy variations and determine a gradient to better understand such loads. The current study objectives are to obtain a numerical evaluation of tubular CFRP structures under low-speed impacts, promote various impacts with different energy levels and correlate with the strain results, define the energy limit that produces residual damage and create a parallelism between the residual strength and fatigue life in experimental testing. Usually, a low-velocity test involves a drop weight test at room temperature. Such impacts can be considered events that occur between 1 and 10 m/s, considering the variation in the properties of the impacting and impacted material. As the contact time between the two is longer (5 to 10 milliseconds) than in the high-speed test, the sample undergoes global deformation in which even internal damage extends beyond the contact zone. There have been studies with relatively similar goals. G. Minak et al. (2009) reiterate that the laminate layer orientations influence the resistance to delamination caused by impact and that although the onset of impact damage is not affected by the torsion load, this effort influences damage propagation. In addition, they found that delamination does not occur between subsequent layers with the same orientation. Marcelo Leite Ribeiro et al. (2015) found that tube layup directly affects sustained damage of flexion in the axial direction, and certain layups are more appropriate for distinct loads and load types. Finally, Lin Shi et al. (2021) conclude that repeated low-velocity impacts cause lower energy absorption capacity and that damage behaviour and residual performance subjected to axial compression are dominated by impact-induced delamination. Although the presented findings are somewhat related to what is expected to be settled, it must be said that there was no intent to assess the effects of invisible damage on the tube, to find energy limits that produce residual