Experimental and Analytical Investigations of the Dynamic Response of Adhesively Bonded Single Lap Joints

Abstract

Dynamic response of single lap joints, subjected to a harmonic peeling load is studied theoretically and experimentally. In the theoretical part, dynamic response of a single lap joint clamped at one end and subjected to a harmonic peeling load at the other end is investigated. Adherents are modeled as Euler-Bernouli beams joined in the lap area by a viscoelastic adhesive layer. Both axial and transverse deformations of adherents are considered in deriving the equations of motion. The effects of adhesive layer thickness, mechanical properties and its loss factor on the dynamic response of the joint are investigated. Furthermore, effects of defects such as a void in the lap area on the dynamic response of the joints are studied. The results showed that frequencies where peak amplitudes occurred were little dependent on the adhesive loss factor. However, peak amplitudes reduced for joints with a higher adhesive loss factor. Furthermore, the results indicated that for the joint geometries and properties investigated the system resonant frequencies were not affected by the presence of a central void covering up to 80% of the overlap length. In the experimental part, single lap joints were fabricated using 6061-T6 Aluminum. Adherents were joined together using Hysol EA 9689 adhesive film. Joints with various central voids were manufactured by removing adhesive film from the desired area of lap joints prior to bonding adherents. Dynamic responses of the joints were investigated using the hammer test technique. The system response was measured using both an accelerometer and a noncontact laser vibrometer. The natural frequencies of the joints obtained by using the laser vibrometer were very close to those obtained theoretically. However, natural frequencies obtained by using an accelerometer depended on the accelerometer location in the system, which was attributed to its mass contribution to the over- all system mass. A central void covering less than 80% of the overlap length had little effect on the system resonance frequencies. This was in agreement with the theoretical results. In contrast total system-damping ratios were a function of the void size. Joints without a void exhibited higher damping.

Analytical model of lap-joint adhesive with embedded piezoelectric transducer for weak bond detection

“…In this case, the mechanical loss factor was not normalized as its value was not reported by the vendor. Nonetheless, various epoxy materials display a value of the mechanical loss factor in the range of 0.005–0.015 (Vaziri et al, 2004) which was chosen as the range of interest for the study. Figure 9(b) suggests that both the conductance, G ( ω ), and the absolute value of the impedance, | Y false( ω false) | , increase as the adhesive’s loss factor increases.…”

“…In this section, the sensitivity of the method introduced in this article with respect to the sliding ratio, χ , is compared to the sensitivity of the reflection coefficient. In the past, various authors (Jiao and Rose, 1991; Nagy, 1991; Pilarski and Rose (1998); Vaziri et al, 2004) proposed using P- and SH-waves to infer the presence of a weak bond at the interface between the adherent and the adhesive. Since SH-waves were shown to be relatively more sensitive to weak interfaces, they were preferred as the method to compare the sensitivity of the technique proposed in this article.…”

Vibration analysis of single lap adhesive joint: Experimental and analytical investigation

“…where, Q q is the shear force & M q (q ¼ 1, 2) the bending moment at the edge of the joint element, A ( ¼ w x t 1 ) is the cross sectional area of the beam, u 1 , u 2 , y 1 & y 2 are the longitudinal and transverse displacements of adherents; shear stress in the bonded area considering longitudinal and transverse displacement can be expressed as (Vaziri et al, 2004)…”

“…The equation of motion was developed using Hamilton's principle. Vaziri et al (2004) developed a model to understand the effects of defects such as a void in the overlap on the system response. The paper by Lin and Tseng-Chung Ko (1997) deals with free vibration analyses of adhesively bonded plates.…”

Experimental validation of numerical structural dynamic models for metal plate joining techniques

“…The structural dynamic behavior of adhesive bonding has been the subject of extensive research (He, 2011). The effect of various adhesive parameters, such as material and geometric properties, on the structural dynamic behavior has been analyzed using analytic models (Vaziri et al., 2004) as well as very detailed FE models (He and Oyadiji, 2001; Kaya et al., 2004; Gunes et al., 2007; He, 2012a, 2014) including validations with experimental measurements of natural frequencies and frequency response functions (Aruleswaran et al., 2001; Vaziri et al., 2004; He, 2012b), mainly for simple beam or plate lap-joint configurations. The FE models used in these studies rely on very refined solid element meshes of the adhesive layer, implying mesh-dependent modeling and computationally expensive models.…”