Influence of temperature and strain rate on cohesive properties of a structural epoxy adhesive

Abstract

Effects of temperature and strain rate on the cohesive relation for an engineering epoxy adhesive are studied experimentally. Two parameters of the cohesive laws are given special attention: the fracture energy and the peak stress. Temperature experiments are performed in peel mode using the double cantilever beam specimen. The temperature varies from −40 to +80 • C. The temperature experiments show monotonically decreasing peak stress with increasing temperature from about 50 MPa at −40 • C to about 10 MPa at +80 • C. The fracture energy is shown to be relatively insensitive to the variation in temperature. Strain rate experiments are performed in peel mode using the double cantilever beam specimen and in shear mode, using the end notch flexure specimen. The strain rates vary; for peel loading from about 10 −4 to 10 s −1 and for shear loading from 10 −3 to 1 s −1 . In the peel mode, the fracture energy increases slightly with increasing strain rate; in shear mode, the fracture energy decreases. The peak stresses in the peel and shear mode both increase with increasing strain rate. In peel mode, only minor effects of plasticity are expected while in shear mode, T. Carlberger (B) SAAB Automobile AB, the adhesive experiences large dissipation through plasticity. Rate dependent plasticity, may explain the differences in influence of strain rate on fracture energy between the peel mode and the shear mode.

Some aspects of cohesive models and modelling with special application to strength of adhesive layers

“…Moreover, temperature and strain rate influence the cohesive laws. In an experimental study (Carlberger et al 2009), it is shown that the peak stress in peel loading decreases monotonically with increasing temperature from −40 • C to +80 • C; the glass transition temperature is about +90 • C for this adhesive. It is also shown that the fracture energy is fairly unaffected by the temperature in this temperature range.…”

“…This explains the peel deformation observed in ENFexperiments (Leffler et al 2007), and the shear hackles or cusps observed on fracture surfaces (Pettersson et al 2006). Moreover, if it is assumed that the plasticity is time dependent in nature, it also explains the difference in influence of strain rate on cohesive laws in peel and shear; experiments indicate a much larger rate dependence on the peak stress in shear than in peel (Carlberger et al 2009). With a smaller strain rate and a viscous type of plasticity, more time is available to decrease the stress resulting in a smaller peak stress.…”

“…Figure 10 shows a number of specimens developed and used to measure cohesive laws. The Double Cantilever Beam specimen loaded with transversal forces (DCB) and bending moments (DCB-M) are developed and used in a series of papers (Andersson and Stigh 2004;Carlberger et al 2008;Sørensen and Jacobsen 1998;Alfredsson 2003;Högberg et al 2007;Andersson and Biel 2006;Carlberger et al 2009;Alfredsson 2004). Both specimens measure the cohesive law in pure peel loading, i.e.…”

Tensile Behaviour of a Structural Adhesive at High Temperatures by the eXtended Finite Element Method

“…The authors concluded that the values of r 0 , G Ic , and w decreased with the temperature. The experimental work of Carlberger et al [14] addressed the r 0 and G Ic dependency on temperature of an epoxy adhesive using the DCB test. The tensile cohesive laws of the adhesive were determined by the direct method and the tensile stress, r n vs. w laws showed an approximate triangular shape.…”

Influence of the temperature on the fracture energy of a methacrylate adhesive for mining applications

“…identified a significant reduction on fracture toughness at −196 °C using carbon fiber adherents and an epoxy adhesive (AF-191M) [18]. Carlberger et al has identified that the fracture energy in the epoxy adhesive XW1044-3 is affected significantly at temperatures between −40 and 80 °C [19]. Furthermore, the combined effect of test speed and temperature on the tensile properties of a high-temperature epoxy adhesive have been studied [20] Tensile tests were performed at three different speeds and various temperatures (Room Temperature (RT), 100, 125 and 150 °C), noting that with increasing temperature, the adhesive becomes ductile, resulting in a higher deformation to breakage; the maximum tensile stress decreased linearly with temperature, while increasing logarithmically with the speed test.…”