Abstract
Although the high performance thermoplastics matrix composites have been studied for more than thirty years, only recently their advantages have been properly perceived and exploited, for a wide range of applications either in secondary either in primary aeronautical structures. In this work, compression testing of a flat panel stiffened with L-shaped stringers made of Polyphenylene-sulfide (PPS) matrix reinforced with carbon fibres, is presented. The stiffeners were joined to the base plate by induction welding, as reported in a former study. The numerical activities, aimed at static, buckling and post-buckling analysis, first of a single stringer, then of the stiffened panel under compressive load, provided results in good agreement with the experimental ones. The analyses were performed taking into account either for the geometric non-linearity associated with the large deformations of the structures under the action of compressive loads either for the local buckling of the flanges composing the stringers. Experimental activities were aimed at the characterization of the adopted materials with a special focus on the determination of buckling loads either of an L-shaped stringer either of a panel stiffened with four stingers. In both cases an excellent structural behaviour was shown, the panel and a single stringer being able to take huge loads after the first buckling appeared. The panel, in particular, showed an excellent post-buckling strength and broke by buckling failure of stringers. The welded interfaces did not fail indicating that thermoplastic welding is a suitable technique for assembly composite structural elements.
Highlights
High performance thermoplastic matrix composites are gaining more and more attention in several engineering applications such as aerospace, wind turbines, and automotive industries
The flexural/torsional buckling is possible for onedimensional elements having low torsional stiffness: if the boundary conditions allow to some extent the torsion of the beam sections, such kind of buckling must be taken into account
In the case of these thermoplastic matrix composites with high post-buckling capability, such a margin turns in an actual safety factor much higher than the nominal one equal to 1.5
Summary
High performance thermoplastic matrix composites are gaining more and more attention in several engineering applications such as aerospace, wind turbines, and automotive industries. Over the last 30 years, thermosetting matrix composites were preferred by the aerospace designers thanks to their dimensional stability at high temperature, since they not melt. Thermoplastics joined thermosets in the comfort zone of the aerospace designers. An example of such a change of perspective is given by the tail plane of the Gulfstream 650 or the leading edge of A380 and A340 both made with polyphenylene-sulfide (PPS) matrix reinforced with carbon and glass fibers, respectively. By induction and resistance welding was adopted for these components (Offringa, 2005)
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