Use of GFRP end wraps to prevent plate debonding

[Chand31]

Hello,

I am modelling the behavior of square hollow steel columns strengthened with CFRP plates in ANSYS Workbench. The CFRP plates are applied on opposite sides of the column to delay the occurrence of overall buckling. I have attached a picture of the cross section to explain the placement of the CFRP plates. My question is that in the current configuration, my model is failing due to debonding of the composite at the plate ends. In order to prevent the latter failure mode, I was wondering if it is beneficial to add 2 GFRP wraps at the ends of the column? The problem is I fail to visualize how these wraps would help prevent the end debonding. I would really appreciate if anyone with more experience could explain more clearly.

 

[SWComposites]

How do you know the ends are debonding? What method/material properties are you using? What is the strain level in the column at max load?

 

[Chand31]

The end debonding is clear because the interfacial shear stress reaches its maximum at the ends first and the adhesive slides as a result (See picture below).

For the material properties, I am using a cohesive zone model (CZM) to simulate the behavior of the adhesive. I am modelling both interfacial shear and peeling stresses. The values input in ANSYS are shown in the table below.

The debonding of the CFRP plates happens well before the peak buckling load is reached and hence, at maximum load level, the strain in the steel column is mostly below yield strain.