New national standard GB/T 46220-2025 for composite material fatigue testing and dynamic fatigue testing machine selection

From March 1, 2026,GB/T 46220-2025 "Test method for initiation of type I fatigue delamination expansion of fiber-reinforced plastic composites"Officially implemented.This is an important new national standard in the field of composite material fatigue testing, which puts forward more standardized requirements for the fatigue performance evaluation of automotive lightweight composite parts.With the widespread use of carbon fiber composites in automobile manufacturing, how to choose the right one?Dynamic fatigue testing machineTo meet the new national standard testing needs, it has become a concern for many companies.

1. Interpretation of the core content of the new national standard GB/T 46220-2025

Scope of application:This standard specifies the method for determining the critical conditions for the delamination of fiber-reinforced plastic composite materials to begin to expand under type I (expanding) fatigue loading.Suitable for carbon fiber and glass fiber reinforced thermosetting/thermoplastic composite materials.

Sample form:DCB (double cantilever beam) specimens were used, with a prefabricated Teflon film sandwich as the initial crack.The width of the specimen needs to be precisely controlled and there should be no delamination or burrs on the edges.

Test conditions:The fatigue load is a sine wave, the stress ratio R=0.1, and the frequency is 5-10Hz.Record the number of cycles when delamination begins to expand and the corresponding strain energy release rate threshold ΔGth.

Differences from the old standard:Compared with the original ASTM D3479/D3479M-19 tensile fatigue standard, the new national standard focuses more on the critical conditions for the initiation and expansion of delamination, with smaller data discreteness and higher engineering reference value.

2. Composite automotive parts testing scenarios

Composite materials in the automotive field are mainly used in: carbon fiber drive shafts, composite leaf springs, battery pack casings, body panels, interior structural parts, etc.These parts are subjected to complex alternating loads during use, and their fatigue performance is directly related to safety.

Test standard combination:In addition to the GB/T 46220-2025 delamination test, it is usually necessary to cooperate with: ASTM D3479 (tensile fatigue S-N curve), ASTM D5528 (delamination fracture toughness), ISO 13003 (rotational bending fatigue).

3. Sample preparation requirements

The precision requirements for sample preparation of composite materials are much higher than those of metals: the cutting edges must be free of burrs and delamination, and it is recommended to use diamond grinding wheels for precision cutting.The prefabricated Teflon film has a thickness of 0.025mm and is located in the middle of the sample.The sample needs to be conditioned in a standard environment (23℃±2℃, 50%±5%RH) for at least 24 hours before testing.

4. Key points for selecting a dynamic fatigue testing machine (special for composite materials)

1. Load accuracy:The delamination test load of composite materials is small (usually 500N-5kN). It is recommended to choose a small force high-precision dynamic fatigue testing machine with a force value accuracy within ±0.5%.

2. Displacement measurement accuracy:Layered expansion measurement requires a high-precision extensometer. It is recommended to equip a non-contact video extensometer or COD gauge with a displacement resolution of ≤0.001mm.

3. Frequency range:5-10Hz can meet the requirements of the new national standard, and there is no need to blindly pursue high frequencies.However, it is necessary to ensure frequency stability, with fluctuation ≤±0.1Hz.

4. Data collection frequency:It is necessary to support the collection of force values and displacements in each cycle to calculate the strain energy release rate in real time.Recommended sampling rate ≥100 points/cycle.

5. Environmental box options:Automotive composite parts often need to be tested in high and low temperature environments (-40℃-120℃), and the compatibility between the environmental box and the host machine needs to be confirmed.

Shandong Huayan Intelligent Equipment GroupThe 20KN electronic servo dynamic fatigue testing machine (0.1-20Hz) perfectly adapts to the new national standard testing requirements of GB/T 46220-2025 and supports high-precision loading with small force values, non-contact displacement measurement, and DCPD crack monitoring.It has provided composite material fatigue testing solutions to many automotive lightweight companies. As a source manufacturer of mechanical testing instruments, it supports non-standard customization.