A cracked plate repaired by bonded reinforcements

Abstract

A plate with a semi-infinite crack is repaired by having reinforcing sheets bonded to its faces, and is subjected to a uniformly distributed tensile load at right-angles to the crack. It is shown that the crack extension force has a finite value, provided that the reinforced structure can still carry the load if the crack, instead of being semi-infinite, runs across the whole plate, cutting it in half. The case of a plate with a crack of finite length is considered next: the determination of the force is reduced to the solution of a Fredholm integral equation, from which the asymptotic behaviour for short cracks is deduced by the method of successive approximations. These results provide an upper bound to the force for arbitrary crack lengths. A comparison with numerical results suggests that this upper bound is sufficiently close to the actual value to be useful in practice. The residual thermal stress induced by the process of bonding, and the resulting force on a crack, are shown to depend sensitively on the nature of the constraint at the edges of the plate, as well as on the extent of the plate outside the heated region. A number of extensions to less idealized configurations are discussed.

Fracture and damage mechanics modelling of thin-walled structures – An overview

“…Conventional linear elastic fracture mechanics has successfully been applied to bonded skin-stiffener connections, particularly for fuselage applications [153]. One application of bonded structures that has received significant attention in the last 15 years is the use of bonded patches to repair aging aircraft structures [154][155]. Analysis of these types of structures consisted of applying the cyclic linear elastic stress intensity factor concept to crack growing in the metallic structure, including a correction to account for the crack bridging effect from the bonded stiffeners or repair patches.…”

Development and Validation of Bonded Composite Doubler Repairs for Commercial Aircraft

“…The difficulties associated with analyzing the stress fields and flaw tolerance of various composite doubler designs and installations are highlighted in references [8][9][10]. Doubler design and analysis studies [11,[18][19][20][21][22][23][24][25] have led to computer codes and turn-key software [26][27] for streamlining the analyses. These developments have taken great strides to eliminate the approximations and limitations in composite doubler DTA.…”

“…[8] and [20], a predictive capability for the growth of cracks repaired with composite doublers was developed using Rose's analytical model [21] and experimental fatigue studies.…”

“…Disbonds can occur between the composite doubler and the aluminum skin while delaminations can develop between adjacent plies of Boron-Epoxy material. It has been shown in related studies that the primary load transfer region, which is critical to the doubler's performance, is around its perimeter [1,13,[20][21][22][23][24]. The purpose of the engineered disbonds in many of the test configurations (see Fig.…”

Elliptical and circular bonded composite repair under mechanical and thermal loading in aircraft structures

“…Recently, the use of adhesives is accepted as a process of structures repairs to increase the service life of damaged components [1][2][3][4][5][6] . The metal or composite patches are stuck on a single or on both faces of the cracked structural components.…”