Issues related to determining effective ultimate strength, making provision for undetectable damage
Piotr Czarnocki, Przemysław Dobrzański
Quarterly No. 4, 2016 pages 238-243
DOI:
keywords: BVID, equivalent hole, detectability
abstract A simplified procedure for determining effective ultimate stress that could account for the adverse effects of undetected damage done to laminates was described. The procedure was based on the assumptions that an equivalent open hole (EOH existed that could appropriately represent the extent of damage for the purpose of calculating strength and that the laminate under consideration was notch sensitive. Particular emphasis was placed on the assessment of BVID extent, which was crucial to define the EOH dimensions. The results of different inspection methods concerning the damage extent were presented and compared with each other. Moreover, it was experimentally shown that for a typical inspection condition the detectability threshold of BVID expressed in terms of indentation depth, δ, and was 262 µm. It was found that the extent of damage defined based on visual inspection was significantly different from that defined based on C-scans and fractographic inspections. It was concluded that to determine the EOH dimensions, the damage measurements were not sufficient while definition of the EOH dimensions could be based on the equal values of the stress concentration factor caused by the damage of a given extent and EOH.