Analytical and Experimental Studies on Delamination Arrest Features in Aircraft Composite Structures

Abstract

Delamination is the critical damage type for integrated carbon fiber structures, which are employed in primary aircraft structures. In order to minimize the danger, one common solution is to install fasteners, clamping the laminate together and partially arresting the delamination. Current research has indicated that multiple fasteners installed in series do not fully arrest delaminations, instead merely slowing and redirecting the propagation of the crack, first by compressing the lamina together and second by transferring load via shear engagement of the fastener. Additional work has found that fastener spacing can be increased beyond the typical spacing of 5 fastener diameters; experimental and computational studies have indicated that the failure mode can be shifted away from delamination under both static and fatigue loading even with a significantly greater fastener spacings. NomenclatureD = Fastener Diameter = Crack growth per cycle = Total Strain Energy Relase Rate = Critical Total Strain Energy Release Rate = Mode I Strain Energy Release Rate = Mode II Strain Energy Release Rate = Critical Mode I Strain Energy Release Rate = Critical Mode II Strain Energy Release Rate

Delamination Arrest by Fasteners in Aircraft Structures Under Static and Fatigue Loading

“…As a result, effort has been put into predicting the fatigue delamination response of composites under various loading conditions. Much of the foundational work revealed that the matrix properties dominated the delamination fatigue response [28] while more recent work found that the introduction of fasteners to the system will alter the response [29] [30].…”