Strength estimation of multi-bolted metal composite joints under combined operation of bearing and bypass stresses | Mekhanika | kompozitsionnykh | materialov i konstruktsii
> Volume 24 > №2 / 2018 / Pages: 266-280

Strength estimation of multi-bolted metal composite joints under combined operation of bearing and bypass stresses

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Abstract:

It is necessary to know the load distribution in the joints elements and predict the failure ways associated with the different types of loads to forecast the damage and failure in composite joints. In the case when, the relation between the bearing stresses to the normal bypass stresses of the hole is high as a rule the failure occurs due to bearing. If this relation is low, the joint is broken down by tension on net-section. The ultimate stresses values of bearing-bypass stresses can be obtained from the experimental diagram of the bearing-bypass destructive stresses. The similar diagrams for carbon fibre-reinforced plastic (CFRP) were obtained by American researchers Grevs and Nike at the first time and have rather complex polygonal view. To get such destruction diagrams, it is required to fulfill a large quantity of experiments on unique experimental facility with two independent loading channels to change independently the bearing and bypass loads simultaneously. Similar experiments require significant financial investments and aren’t always available to researches. The well-known joints strength calculation method, using the finite element method in combination with experimentally obtained diagrams of the bearing-bypass load capacity is modified in the work. A quadratic approximation of intermediate values is proposed to describe bearing-bypass diagram by isolated experimental or calculated data on the bearing and bypass destructive stresses values. The results of the similar approximation describe the Grevs and Nike polygonal relation quite well as almost all points of the obtained diagrams keep within the spread of the experimental results of these authors. The obtained technique allows to refuse from bearing-bypass diagram construction with application complex multichannel experimental facilities, and thereby save resources significantly at the designing of the new equipment units.

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