Co-authors​ :

 Jannis HÜPPAUFF (GERMANY), Vinay NAGARAJ (GERMANY), Thomas VINAY NAGARAJ (GERMANY), Thomas VINAY NAGARAJ  

The continuity of the fuselage skin on an aircraft is consistently disrupted by various cut-outs, including doors and windows. These interruptions pose challenges due to the operational loads (maneuvering, cabin pressure etc.) experienced by the fuselage, leading to the critical stresses and deformations around these cut-outs. To address this issue, a door-surround-structure (DSS) is employed to reinforce the door cut-out and withstand the induced stresses. Traditionally, the door-surround-structure has been developed using a differential design involving either metal or thermoset composite materials. This structure consists of several segments, such as sills, lintels, and intercostals, which are assembled using mechanical rivets. These differential designs have different drawbacks. Assembly requires many steps, which increases the overall production time. In addition, the rivets weaken the continuous FRP structure and lead to increased stresses. The rivets also increase the overall weight. The utilization of thermoplastic composites presents a promising alternative, allowing for various joining methods, including welding and co-consolidation. Additionally, thermoplastic composites offer the advantage of shorter manufacturing cycle times. Recognizing these benefits, a new integrated thermoplastic door-surround-structure for a single-aisle aeroplane has been developed. The design process is supported by numerical simulations, which play a crucial role in ensuring the structural integrity and performance of the thermoplastic door-surround-structure. This involves conducting precise strength analyses to accurately capture the nonlinear behaviour of the mechanical material until failure. The initial failure in such structures often manifests as inter-fibre failures. However, in multidirectional laminates, this does not necessarily lead to an overall laminate failure. To comprehensively understand the structural behaviour and guarantee the absence of catastrophic ruptures or unacceptable deformations, incremental failure analyses of the door-surround-structure are employed. These analyses involve a step-by-step examination of the structure's response to varying loads and conditions, providing insights into potential failure modes and allowing for necessary adjustments in the design. In summary, the development of an integrated thermoplastic door-surround-structure represents a significant advancement in addressing the challenges associated with cut-outs in aircraft fuselage skin.