Design of damageable aircraft polymer composite structures with a high strength and enhanced service life

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Design of damageable aircraft polymer composite structures with a high strength and enhanced service life

Ushakov, A.E.

Data from experiments with PMC (polymer matrix composite) aircraft structures and from service records have shown that, considering both the brittle behavior and the high fatigue resistance the damage initiation and growth mechanisms for the most of the current polymer composites differ fundamentally from fatigue failure of metals. It has been noted that damages in PMCs are not due to periodic airframe loading but to random mechanical impacts, that may occur at any stage of structure manufacturing and service for instance impacts during assembly or collisions with stones or hailstones. Full-scale structure tests were realized during the certification of the PMC aileron structures of the passenger aircraft Tu-204 and of wing and stabilizer of the performance-type glider LAK-12. The size of the damages and the type of the defects simulating them, the value of applied loads for each damage case are determined in a special analysis using the service experience, control- and maintainability of PMC aircraft structures, their failure after effects on general aircraft reliability and safety. The effectiveness of unidirectional carbon fiber strips used as crack stoppers and formed in booms of carbon fiber spars and ribs and which reinforce the low-modulus carbon fiber skin is verified by survivability tests and service experience of the wing and forebody section of e.g. the A 300/A 310 fin.