Overview
ISO 22838:2020 specifies a standardized test method for determining the adhesive fracture energy of adhesively bonded plates of carbon fibre reinforced plastics (CFRPs) and metal using double cantilever beam (DCB) specimens. The standard covers specimen manufacture and conditioning, test apparatus and setup, precracking and re-loading procedures, measurement of compliance and curvature, and data analysis to produce fracture energy (G) values and R‑curves for both crack initiation and stable crack propagation. It is also applicable to metal bonds with other composites (e.g., GFRP).
Key technical topics and requirements
- DCB specimen design and preparation: guidance on geometry, insert (starter film) use, and measurement of crack and precrack lengths.
- Test apparatus and machine requirements: crosshead displacement control, fixtures for load introduction, and calibration/verification references.
- Precracking and initiation procedures: methods to create a reliable starter crack or non‑adhesive insert to measure initiation toughness.
- Compliance and curvature measurements: measurement of machine and specimen compliance, and correction for thermal expansion‑induced curvature between metal and composite beams.
- Thickness ratio management: procedures to select beam thickness ratio (h1/h2) to avoid plastic deformation of metal arms during propagation.
- Data analysis methods: calculation of adhesive fracture energy using Corrected Beam Theory (CBT) for identical thicknesses, modified beam theory for dissimilar thicknesses, and the area method; extraction of initiation and propagation values and construction of R‑curves.
- Precision and reporting: minimum reporting content, statistical precision considerations, and annexed workflows and compliance measurement methods.
- Safety and environmental notes: standard highlights normal laboratory practice and appropriate waste disposal.
Practical applications
- Evaluating adhesive performance in CFRP–metal bonded joints used in aerospace, automotive, marine and civil structures.
- Supporting design validation, type certification, and qualification of bonded assemblies.
- Guiding maintenance, repair and overhaul (MRO) procedures and assessing repair methods (e.g., pipework, bridge components).
- Material selection and quality control in manufacturing and R&D laboratories assessing interfacial toughness, bond durability and failure modes.
Who should use this standard
- Materials and structural test laboratories
- Aerospace and automotive engineers responsible for bonded joint design and certification
- Adhesive and composite manufacturers
- MRO organizations and structural integrity assessors
- Researchers studying interfacial fracture mechanics of composites and hybrid joints
Related standards (reference)
- ISO 25217 - DCB/TDCB methods for structural adhesives
- ISO 291 - Conditioning and testing atmospheres
- ISO 7500‑1 - Calibration of testing machines
- ISO 10365 - Adhesive failure pattern designation
Keywords: ISO 22838:2020, DCB, double cantilever beam, adhesive fracture energy, CFRP, carbon fibre reinforced plastics, bonded plates, CFRP–metal joints, corrected beam theory, R‑curve.
Open preview (PDF)Composites and reinforcements fibres — Determination of the fracture energy of bonded plates of carbon fibre reinforced plastics (CFRPs) and metal using double cantilever beam specimens