GB/T 45877-2025 in English
VALIDCarbon fiber composite materials—Method for planar biaxial tensile testing of laminates
- Issued on:2025-06-30
- Implemented on:2026-01-01
- File Format:PDF
- Delivery:Via email within 5 business days
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《GB/T 45877-2025碳纤维复合材料 层合板平面双轴拉伸试验方法》由TC572（全国碳纤维标准化技术委员会）归口，主管部门为国家标准委。
Introduction
Technical background and evolution of the standard
This standard systematically specifies the test method of carbon fiber composite materials under biaxial stress state for the first time, filling the standard gap in the domestic biaxial testing machine application field. Compared with uniaxial test standards such as ISO 527-5, its innovation is reflected in:
| Comparison Dimensions | Traditional Uniaxial Standards | GB/T 45877-2025 |
|---|---|---|
| Stress State | Uniaxial Loading | Orthogonal Biaxial Simultaneous Loading |
| Specimen Form | Strip Specimen | Cross-Shaped Specimen with Reinforcement Plates |
| Strain Measurement | Uniaxial Strain Gauge | DIC or Triaxial Strain Gauge |
Analysis of core test requirements
5.1 Key parameters of biaxial testing machine
The standard puts forward strict requirements for biaxial testing machine:
- Flatness error ≤0.1mm (coplanarity of the four clamping ends)
- Loading axis verticality error ±0.1°
- Must be equipped with hydraulic wedge grips to prevent slippage
Case: In the test of the wing skin of a certain model of aircraft, the use of substandard equipment resulted in a variance coefficient exceeding 30%. After replacing it with equipment that complies with Clause 5.1, the coefficient of variation dropped to below 8%.
Key technologies for specimen preparation
6.2.3 Specifications for reinforcement sheets
The design of the reinforcement sheet directly affects the stress concentration in the test area:
- The thickness needs to be 2-3 times of the specimen body (2.5 times is recommended)
- Diamond opening 50±0.5mm with a 30° slope transition
- Material can be titanium alloy or 0/90 laminated composite material
Appendix A specifies the secondary bonding process in detail:
| Process parameters | Vacuum negative pressure curing | Autoclave curing |
|---|---|---|
| Pressure requirements | ≥-80kPa | 600kPa+vacuum |
| Temperature range | 25-250℃ (depending on film specifications) | |
Comparison of strain measurement technologies
DIC technology advantages: It can obtain full-field strain distribution, which is particularly suitable for shear strain analysis in the 45° direction; while triaxial strain gauges are more suitable for high-frequency dynamic testing.
The standard stipulates the calibration requirements for two measurement systems:
- DIC system: Reprojection error <0.15
- Strain acquisition system: Linearity deviation ≤0.5%FS
Implementation suggestions
Solutions to common problems
| Problem phenomenon | Possible cause | Solution measures |
|---|---|---|
| Damage in non-assessment area | Insufficient stiffness of reinforcement plate | Increase the thickness of titanium alloy plate |
| Strain difference ratio >10% | Specimen buckling | Check the centering or thicken the specimen |
Note: It is recommended to perform preload verification (Clause 9.4) before the first test to ensure system linearity.
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