Computational and experimental evaluation of fatigue life characteristics of the transport category aircraft composite wing panels

Aeronautical and Space-Rocket Engineering

Design, construction and manufacturing of flying vehicles


Аuthors

Tudupova A. N.*, Strizhius V. E.**, Bobrovich A. V.***

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: ayunatudu@ya.ru
**e-mail: vitaly.strizhius@gmail.com
***e-mail: bobravd@gmail.com

Abstract

At the preliminary design stage of the aircraft (up to the detailed design stage and performing full-scale fatigue tests of airplane glider units), it is necessary to ensure the fulfilling requirements for fatigue and survivability of composite aircraft structural components. To start with, a computational evaluation of safe life span and damages non-progression in structural elements from polymer composite materials (PCM) should be performed.

The following evaluations should be performed to this end:

  1. Computational and experimental evaluation of the safe resource of elements of composite aircraft structures.

  2. Computational and experimental evaluation of non-progression of the first category of damage on the elements of composite aircraft structures over the entire period of the aircraft operation (up to reaching the operating time equal to the design service life of the aircraft).

  3. Computational and experimental evaluation of non-progression of the second category of damage on the elements of composite aircraft structures over the period between scheduled or targeted inspections, conducted through the certain intervals.

This article presents the basic regulatory requirements, methods and procedures for computational and experimental evaluations of the main fatigue life characteristics of composite wing panels at the outline design stage of a transport category aircraft. The example of computational and experimental evaluations of the safe resource and the frequency of inspections of the upper composite wing panel of a transport aircraft made of the AS4-PW carbon fiber laminate is presented. A number of important inferences was drawn.

The obtained results of computational and experimental evaluations of the life span characteristics of the upper composite panel of a wing from the AS4-PW carbon fiber laminate at the stage of outline design of the aircraft allow making the following conclusions:

  1. The expected safe resource of the upper panel is being actually determined by the computed safe resource of the panel in the zone of impact damage of the BVID type, which the value is 6.7 times less than the calculated safe resource of the upper panel in the free holes zone.

  2. The frequency of necessary inspections of the upper panel is determined, first of all, by the frequency of inspections of the panel in the impact damage zone of the VID type. The frequency of inspections is 5,300 flights and it actually determines the frequency of inspections according to the C-check maintenance form.

The obtained values of the safe resource and the frequency of inspections are within the range of real values of the life fatigue characteristics of the real aircraft, which allows concluding on the acceptability of such evaluations.

Keywords:

layered polymer composite materials, fatigue life, S-N curve, damages non-progression approach, safe-life, inspections frequency

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