Damage evolution behavior of bi-adhesive repaired composites under bending load by acoustic emission and micro-CT

In the field of composites patch repair, it is necessary to improve the repair performance of adhesive due to its important role in repair efficiency and durability. A bi-adhesive repair construction with two adhesives was designed and the carbon nanotubes were firstly applied in this bi-adhesive to carry out composites patch repair in this paper. Mechanical behaviors and deformation damages of different repair configurations under three-point bending loads were investigated using acoustic emission and X-ray micro-computed tomography. Failure mechanisms were deeply discussed through the analyses of characteristic signals and three-dimensional visualization of interior damage. The damage evolution behaviors were divided into three stages patch damage and edge debonding, further damage accumulation in adhesive layer and matrix, completely patch debonding and delamination by the clustering analysis and characteristic response of acoustic emission signals. Failure characteristics of scanning images on the adhesive interface and delamination interface revealed the changes of damage modes within different repaired specimens. The damage visualization analyses of X-ray micro-computed tomography was corresponding to the acoustic emission response of interior damage within repaired composites. A combination of these two technologies successfully realized the damage evolution in repaired composites, helping understand the evolvement rule of damage on the adhesive interface.