Experimental investigation of adhesively bonded patch repair of an inclined center cracked panel using DIC

Abstract

Repair of a cracked aircraft structure by an adhesively bonded composite patch has gained lot of importance in extending the fatigue life as well as improving the structural integrity of it. In the present work, an experimental study is carried out using digital image correlation (DIC) technique to analyze the behavior of single and double-sided adhesively bonded patch repair of an inclined center cracked aluminium panel subjected to uniaxial tensile loading. Further, the shear strain distribution in the adhesive layer is also estimated using the DIC technique. Shear strain concentration at the overlap edge in the adhesive layer is very high leading to patch debonding. Further, optimum patch dimension and patch thickness for the given cracked panel are arrived using a genetic algorithm-based optimization technique in conjunction with finite element analysis (FEA). With the optimum patch configuration, a 3-D FEA is further carried out and the obtained results are compared with the experimental prediction from DIC. The DIC prediction correlates with FEA contours on overall basis.

Parametric investigation of one-sided composite patch efficiency for repairing crack in mixed mode considering different thicknesses of the main plate

“…The higher SIF on the unpaired side compared to the unrepaired state is also reported in the previous references. 6 However, in most portion of the main plate thickness, the RF I value is positive, and the results presented in various references, show that the use of the one-sided patches is useful in extending the fatigue life of the structure. 26 For the boron-epoxy patch, the RF I values on the patched and unpatched sides is 61.4% and À33.5%, respectively, and the average SIF in mode I is 198:7 MPa ffiffiffiffiffiffiffiffi mm p , which is 14% less than the unrepaired value.…”

“…Anyway, the metal patch does not form in any shape as easy as a composite patch. 6 Repair strength depends on the adhesive strength, patch strength, and strength of the repaired structure and all three should be examined. There is an asymptotic value for SIF in structures containing crack repaired with the composite patch, and as long as the SIF is below this value, the method is conservative.…”

A review on composite patch repairs and the most important parameters affecting its efficiency and durability

“…There are two approaches for predicting the adhesive separation behavior: the first is the reduction of the adhesive material properties and the second is the use of the cohesive zone modeling. 6 The experimental results indicate that the fatigue life is significantly reduced by the presence of an initial adhesive disbond. 49 Results presented in MoradiMir and Safizadeh 50 show that using the polyurethane sheet instead of the Teflon sheet can provide much more realistic simulation of debonding defects in composite patch subjected to thermography inspection.…”

“…5 A metal patch does not easily form in any shape as a composite patch. 6 In structures containing crack repaired with the composite patch, there is an asymptotic value for SIF, and as long as the SIF is below this value, the repair is conservative (Figure 1). 7 The repair material must have a minimum load-bearing capacity equal to the base material.…”

Bonded composite patch repair’s fiber VF effects on damaged Al-plates fatigue employing a multi-scale algorithm

“…The FE model consists of three parts including the cracked plate, the adhesive and the composite patch (Figure 3). For capturing very high stress gradients near the crack tip, a very fine meshing has been carried out around it, as mentioned in Srilakshmi and Ramji, 25 which is depicted in Figure 4(a). C3D20R elements are used around the crack to achieve more accurate results, and the elements around the crack tip are single and triangular.…”