BS ISO 22838:2020 pdf free.Composites and reinforcements fibres一Determination of the fracture energy of bonded plates of carbon fibre reinforced plastics [CFRPs) and metal using double cantilever beam specimens.
BS ISO 22838 A double cantilever beam (DCB) specimen is used to determine the adhesive fracture energy of structural bonded joint between a metal and CFRP components Resistance to both crack initiation and propagation is determined. The resistance to crack initiation  is determined from both a non-adhesive insert placed in the adhesive layer and from a precrack. The resistance to crack propagation is determined from the precrack. The adhesive fracture energy versus applied opening load is estimated and a resistance-curve (R-curve), i.e. a plot of the value of the adhesive fracture energy versus crack length, is determined. In the case where the CFRP/metal interlaminar toughness and interface are significantly tough, the  plastic deformation of the metal beam preferentially occurs during the crack propagation. This causes  the overestimation of fracture energy values. In such cases, double cantilever beam specimens with dissimilar thicknesses shall be used. An appropriate ratio of the two beams thickness (h1/h2) shall be determined such that the plastic deformation of the metal beams during the crack propagation is avoided.  Most adhesives absorb small quantities of water from the atmosphere which can have a significant influence on the measured properties. Following specimen preparation, the adhesive will generally be dry. If testing is carried out within a few days of specimen manufacture, then it is not necessary to condition the specimen under controlled humidity since negligible absorption of water takes place in the thin adhesive layer. However, if the specimen is tested after longer times or if the influence of absorbed water on the properties is of interest, then the humidity shall be controlled by conditioning and the properties will depend on the conditioning time (see ISO 291). BS ISO 22838 pdf download.