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GB/T 46221-2025Test method for mode III interlaminar fracture toughness of fiber-reinforced plastic composites (English PDF)

纤维增强塑料复合材料III型层间断裂韧性的测定

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Issued by

SAMR; SAC

Level / Type

National · Recommended

Issue date

August 29, 2025

Implementation date

March 1, 2026

Scope

GB/T 46221-2025 is the English-translated version of 纤维增强塑料复合材料III型层间断裂韧性的测定.

GB/T 46221-2025 is the Chinese national standard covering the tearing mode of delamination, where the two plies slide across each other along the crack front — the edge ring cracked disc specimen with its insert and central bonded area, the torsion testing machine and the fixture that grips the disc, the conditioning, the loading and the crack propagation record, and the calculation of the critical strain energy release rate in mode III. Written for laminates from prepreg autoclave moulding, with other processes to follow the same procedure. First edition, under the China Building Materials Federation. In force from 1 March 2026. Issued on 29 August 2025, it has been in force since 1 March 2026.

Document preview — GB/T 46221-2025

National Standard of the People's Republic of China

ICS: 83.120
Classification: Q 23

Issued by: State Administration for Market Regulation; Standardization Administration of the PRC

PrefaceIII
1 Scope1
2 Normative References1
3 Terms and Definitions1
4 Principle1
5 Samples2
6 Test equipment3
7 Test conditions4
8 Experimental Procedure4
9 Result Calculation 6.7
10 Test Report7
Appendix A (Normative) Type III Interlaminar Fracture Toughness Testing Fixture8

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents". Drafting.

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the China Building Materials Federation.

This document is under the jurisdiction of the National Technical Committee on Standardization of Fiber Reinforced Plastics (SAC/TC39).

This document was drafted by: Hebei University of Technology, Beijing University of Aeronautics and Astronautics, China Ordnance Industry Navigation and Control Technology Research Institute, and China Aerospace Science and Technology Corporation.

Institute of Mechanical Strength, Tianjin Aishida New Materials Technology Co., Ltd., Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Beijing Institute of Fiberglass Testing Center Co., Ltd., Chongqing University, Beijing Fiberglass Research and Design Institute Co., Ltd.

The main drafters of this document are: Zhao Libin, Gao Yuan, Liu Fengrui, Jia Ruodi, Yang Shengchun, Liu Qian, Zhu Yingdan, Yang Dexu, Wang Suian, and Gong Yu.

Song Guibin, Han Yu, Xu Haibing, Yu Zongzhi, Zhang Zheyi.

Fiber-reinforced plastic composites type III interlaminar Determination of fracture toughness

1 Scope

This document describes the principle, sample, and method for determining the Type III interlaminar fracture toughness of fiber-reinforced plastic composites using the edge ring crack torsion method.

Test equipment, test conditions, test procedures, result calculation, and test report.

This document applies to the measurement of interlaminar fracture toughness of Type III fiber-reinforced plastic composite laminates prepared by prepreg autoclave molding process.

For fiber-reinforced composite laminate samples prepared by other molding processes, the same procedure applies.

2 Normative references

GB/T 1446

GB/T 3961

GB/T 28889

GB/T 38537

3 Terms and Definitions

The terms and definitions defined in GB/T 3961 and the following terms and definitions apply to this document.

3.1 Type III crack tearing mode

Tear fracture mode caused by torsional load parallel to the tangent direction of the crack leading edge face within the crack plane.

Note. Abbreviated as "Type III mode".

3.2 KIII

The magnitude of the stress field at the ideal crack tip under the Type III mode (3.1).

Note. The stress intensity factor is a function of force, crack length, and the shape and size of the specimen.

3.3 GIIIC

The critical value of strain energy release rate when delamination cracks begin to propagate under the Type III mode (3.1).

Note 1.The strain energy release rate of type III is the rate of change of the strain energy of the specimen with crack propagation under type III mode.

Note 2.The unit is joules per square meter (J/m2).

4 Principles

By introducing circumferential pre-cracks through inserts, symmetrical and balanced composite laminate specimens with edge circumferential cracks were formed (as shown in Figure 1).

(See diagram). A torsion testing machine was used to clamp the specimen-fixture assembly. A type III delamination load was introduced through torsional loading, and the composite material was measured.

Type III interlaminar fracture toughness.

5 Samples

5.1 Sample shape and size

The schematic diagram of the specimen is shown in Figure 1.The specimen is a square (or circular) composite laminate of uniform thickness, and the side length (or diameter) a of the specimen is...

(120±0.5)mm, the sample thickness should not exceed 10mm for 2h. An insert prefabricated portion is introduced outside the circular central bonding area on the middle surface of the sample.

The layer has a central bonding area radius r of (25±1) mm, and the thickness of the embedding should not exceed 10 µm. The sample coordinate system is shown in Figure 2.

a) Front view of a square specimen b) Front view of a circular specimen

c) Top view of a square specimen d) Top view of a circular specimen Index number explanation. 1 --- Embedded object; 2 --- Central bonding area;

a --- Sample side length or diameter;

r --- Radius of the central bonding area of the sample; 2h --- Sample thickness.

Figure 1 Schematic diagram of the sample

......
This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.

Referenced standards

Normative references

GB/T 28889

Cited by

GB/T 46222-2025Test method for mixed mode I-III interlaminar fracture toughness of fiber-reinforced plastic composites

Editions of GB/T 46221

Edition	Title	Revision	Status
GB/T 46221-2025	Test method for mode III interlaminar fracture toughness of fiber-reinforced plastic composites	current edition	Current

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