On the dynamic response of adhesively bonded structures

Abstract

Fracture mechanics experiments are used to investigate the rate-dependent failure of adhesively bonded structures under different deformation modes: I, II and I/II. First, the high-rate mechanical response of the adhesive interface is analysed with a newly developed method -which relies entirely upon digital image correlation. The method was purposely designed to avoid any dynamic effects which may be present. This novel method is verified against quasi-static standard methods showing good agreement. Finally, simulations of the experiments are used to validate a cohesive zone model of the adhesive. The ability of the model to predict cohesive failure under a wide range of strain rates and deformation modes is demonstrated.

Multi-material adhesively bonded structures: Characterisation and modelling of their rate-dependent performance

“…Although, adhesive joints are normally designed to exhibit advantageous shear loading behaviour (mode II), their performance in normal loading (mode I) remains critical. Moreover, both the bond strength and the fracture energy can exhibit rate-dependent behaviour -this has been observed both in metal-to-metal [31,32,33,34,35,27] and composite-to-composite [36,37,38,39] adhesive joints. Therefore, in order to understand the mechanical performance of multi-material adhesive joints, it is necessary to investigate their behaviour under different fracture modes and loading rates.…”

“…Also, the experimental setup for performing rate-dependent investigations is explained. Then, a special data acquisition method developed for dynamic fracture mechanics experiments is described [34]. Finally, the high-resolution method employed to analyse the fracture mechanisms is explained.…”

“…The measured adhesive layer thickness of the manufactured specimens is reported for each fracture mode in Figure 2 was marked with a ruler as it is shown in Figure 3. The HR experiments were carried out using a Split Hopkinson Pressure Bar (SHPB) to subject the specimen to a velocity of v = 4000 mm/s [34]. Images were recorded using two high-speed cameras: a Photron SA-5 camera recorded the displacement of the loading wedge/pin at 150,000 frames per second with a resolution of 716 x 624 pixels while a Specialised Imaging Kirana camera monitored the crack length growth at 200,000 frames per second with a resolution of 9244 x 768 pixels.…”

“…The quasi-static (QS) force-displacement curves for ENF and SLB experiments can be measured directly from the testing machine and DIC output. However, for QS WDCB experiments and for all high-rate (HR) experiments, the force and displacement measurements were obtained from DIC because the measured load values are influenced by friction between wedge and adherent as well as the often unreliable force readings using strain gauges in the SHPB [34]. Therefore, gray scale recordings from one-camera system for the QS and two-camera systems for HR experiments were used to determine both the applied displacement and the crack length.…”

“…Figure 4 explains schematically this measurement method. Detailed information about this method and its relevant equations and approaches can be found in previous work from the authors [34].…”