Overview
ISO 24360:2022 specifies a standardized test method for determining the cross tension strength (CTS) of bonded assemblies between carbon fibre reinforced plastics (CFRPs) and metals. The standard defines specimen designs, preparation, conditioning and testing procedures for a cross‑tension test using a standard specimen loaded in cross tension. It applies specifically to bonded plates used to join CFRPs to metal components and is intended to support reliable, comparable strength data for engineering, certification and quality control.
Key topics and requirements
- Test principle: Measure the maximum cross tension force on a standard cross specimen and calculate CTS as the maximum force divided by the bonded area (MPa).
- Specimen types: Two specimen preparations are described (Type A - bonded coupons; Type B - cut laminate cross specimen). Notches and ply cuts are specified to create the cross‑tension geometry.
- Bonded area: Square bonded area is 25 mm × 25 mm (lapped area). A round bonded area (Ø 20 mm) is recommended to reduce scatter in CTS results (Annex A).
- Number of tests: A minimum of 5 valid test results is required to compute statistical values (mean, standard deviation).
- Test modes and equipment: Tests may be performed in tensile or compressive clamp configurations. Force measurement systems shall comply with ISO 7500‑1 class 1 accuracy. Tests are performed at room temperature and a load–displacement curve should be recorded.
- Failure classification: Record failure modes in accordance with ISO 10365; any non‑standard failure behavior must be reported.
- Test report content: Mandatory items include reference to ISO 24360:2022, bonding process and conditions, materials, specimen dimensions, bonded area shape/size, individual CTS values, mean and standard deviation, failure descriptions and any special remarks.
Applications and users
ISO 24360:2022 is practical for:
- Aerospace and transport manufacturers using CFRP–metal assemblies where bonded joints are critical.
- Materials and structural test laboratories performing comparative adhesive‑joint testing.
- Design, certification and quality teams (type certification, MRO - maintenance, repair and overhaul) needing validated joint strength data.
- Adhesive and surface treatment developers evaluating bonding processes and surface preparation effects on joint strength.
Benefits include enabling reliable comparison of CFRP–metal bond strength, detecting degradation or ionic migration issues in adhesive layers, and supporting conformity evidence for engineering certification.
Related standards
- ISO 7500‑1 - Calibration and verification of static uniaxial testing machines (force measurement accuracy).
- ISO 10365 - Adhesives - Designation of main failure patterns (failure classification).
Keywords: ISO 24360, CFRP, carbon fibre reinforced plastics, cross tension strength, CTS, CFRP‑metal assemblies, bonded plates, adhesive joints, test specimen, bonded area, ISO testing standard.