Investigating De-Bonding Using an Impact Loaded Blister Test

Abstract

Background

De-bonding is a commonly observed failure in adhesively bonded system under impact loading. Therefore, it is important to understand such failures for properly designing and evaluating the integrity of these systems.

Objective

An Impact Loaded Blister Test (ILBT) is proposed to investigate de-bonding under impact loading and to obtain the de-bond initiation toughness. Further the Cohesive Zone (CZ) parameters for de-bonding are also determined.

Methods

An adhesively bonded steel-Poly Metha Methyl Acrylate (PMMA) system was used for tests. A polycarbonate (PC) loading bar, impacted by another PC bar, was used to load the PMMA layer and initiate growth of an existing de-bond. From the strain history measured at mid-length of the loading bar, the load and load-point displacement histories were calculated. The critical energy release rate at the instant the de-bond starts to grow was calculated through an axisymmetric analysis. Finite element analysis (FEA) with CZ was carried out and the remaining parameters of CZ were obtained by inverse approach.

Results

High-speed imaging of the de-bonding processes indicated a circular de-bond growing radially outward. Load-point displacement rate as high as 3.5 m/s was achieved. De-bond growth rate of 115 m/s and de-bond area growth rate of 8 m²/s were achieved. CZ parameters obtained through inverse approach were able to accurately predict the debonding observed in experiment.

Conclusion

The ILBT is demonstrated for isotropic material as a promising technique for determining the de-bond toughness and the CZ parameters of adhesively bonded systems under displacement rate comparable to that encountered in impact like situations.