Modeling overlap and scarf repairs on sandwich composite structures

Abstract

It is well known that sandwich composite structures are easily damaged by low-velocity impact. Drastic reduction of the residual strength can occur, specifically under compression loads [1], [2]. Consequently, it is necessary to develop repair methods so that costly components are not scrapped due to in-service damage. The two major repair configurations for sandwich structures namely overlap and scarf repair, are studied. Using the ABAQUS software the behaviour of a repaired sandwich beam subjected to four point bending is simulated considering two dimensional nonlinear material and geometrical analysis. The objectives of this work are to evaluate the stress distributions and the residual strength of the repaired beam. The influence of several parameters like geometrical alterations on the patch and parent material, size and lay-up of the patch, type of adhesive and its thickness are evaluated in order to optimize the repair efficiency. A comparison between the two different repair methods is also performed in terms of characteristics and advantages for each one, specifically about strength, efficiency and shear and peel stress distributions. Special developed interface finite elements including a cohesive mixed-mode damage model based on the indirect use of Fracture Mechanics[3], were incorporated in the ABAQUS software allowing to simulate damage initiation and growth , to evaluate the influence of the mechanical properties of the adhesive and interfaces on the joints strength, as well as to simulate the several types of fracture. Conclusions were drawn about design guidelines of the sandwich composite repair.