دانلود رایگان مقاله خود ترمیم آوندی در فیبر کربن تقویت شده استرینگر پلیمر اجرای پیکربندی

Abstract

Stringer debonding within stiffened, assembled aerospace structures is one of the most critical damage scenarios that can occur in such structures. As a result, a degree of redundancy is inherently built-in to the design process of skin-stringer configurations to mitigate against premature and in-service failure. Introducing a “self-healing” solution for stringer run-out configurations has the benefit of mitigating and controlling damage initiation, and by introducing this concept there is great potential to reduce excessive conservative safety margins that could ultimately lead to more lightweight designs. Vascular self-healing technology has been successfully implemented into a simplified strap lap specimen, showing that the introduction of a vascular microchannel reduces the strength by 15% but has little effect on the stiffness. Upon delivery and cure of epoxy-based self-healing agents full recovery of the mechanical properties was observed. This self-healing approach has been further implemented into industrially relevant, larger stringer run-out panels as a feasibility study, in which no knockdown to mechanical properties caused by the embedded vascular microchannels has been observed, this study has also shown similar promising results in terms of performance recovery.

4. Conclusions

Stringer run-out damage mechanisms have been simulated using a small scale, strap lap specimen in order to assess the potential for self-healing using an in-situ vascular network. The introduction of a non-optimised vascular network (in terms of location and orientation) had marginal influence on the global mechanical properties: a reduction of approximately 15% in initial debonding strength and 10% in final failure load. By reducing the diameter of the vascule, changing its position or locally aligning with the host ply, there is scope to further reduce, or eliminate, the network's effect on the mechanical performance. In terms of property recovery, the initial stiffness was fully restored and the strength, in terms of initial disbonding, was increased due to the localised improvement in fracture toughness. In order to demonstrate the potential to transfer these findings to larger, more realistic composite assemblies, two stringer run-out panels were manufactured, one as an unmodified baseline and another containing a vascular network. Both configurations behaved similarly and effective healing was observed. A similar damage pattern was observed as found for the simpler strap lap specimen, thus it can be surmised that a similar magnitude of healing recovery could be achieved. Future work will focus on optimising the vascular approach for the stringer run-out assembly, and consideration given as to how an autonomous sensing-healing system could be incorporated to increase the reliability and robustness of this technology and drive it towards industrial exploitation.