摘要

Stiffened metal fan casing was extensively utilised for containment system in fan blade out events. In this paper, ballistic impact tests were carried out on aluminium alloy plate with different types of stiffener. The ballistic limits and energy absorption of each type plate were determined and compared. The transformation of damage mechanism and failure modes of stiffened plate were also addressed. It is concluded that the failure modes of flat plate and stiffened plates are mainly petaling failure, and the shear plugging failure becomes evident with the increase of impact velocity. The ballistic limit of stiffened plate increase 25% higher than the flat plate and the critical impact energy is lifted by 56.3%-62.5% correspondingly with only 8.9% weight increment. There are very small differences of ballistic limit between different types of stiffened plates. The existence of the stiffened bar alters the failure modes and the cracking propagation direction decreases the deflection of target under impact, and further restricts the cracking propagation along the longitudinal direction. For L-type stiffened plate and T-type stiffened plate, the failure modes are dominated by ripping and petaling failure, while the shear plugging failure mode is more obvious for I-type stiffened plate.