ASTM D6671 Mixed-Mode bending Fracture Toughness

ASTM D6671 is a standard test method that establishes the short-term hydraulic failure pressure of thermoplastic pipe, tubing, and fittings, reinforced thermosetting pipe, and reinforced thermoplastic pipe.

TRUSTED BY ENGINEERS FROM

Scope

ASTM D6671 is a standard test procedure for determining the Mixed Mode-1 to Mode-2 Interlaminar Fracture Toughness of Unidirectional Fibre Reinforced Polymer Matrix Composites. This method is designed to use unidirectional carbon fiber tape laminates with brittle and tough single-phase polymer matrices. The procedure can also be used for adhesive joint testing. It can also be used for other types of toughness values and different classes of composite materials, though some irregularities have been noticed in them.

Knowledge of interlaminar fracture resistance of composite materials is useful for determining damage tolerance and durability analyses, which in turn are used in product development and material selection.

Here, Mode-1 is the crack opening mode, in which delamination faces open away from each other and no relative crack face sliding occurs. Mode 2 is the crack sliding mode, in which delamination faces slide over each other, and no relative crack face opening occurs.

Test Procedure

The width and thickness of each test specimen are measured, after which the delamination insert is marked. The length of the lever of the MMB apparatus is set to get the desired mode mixture. The specimen is placed and firmly fixed in the apparatus. Load is applied to the specimen. Applied force versus load displacement, as well as the length of the propagating crack, are recorded. Finally, the specimen is removed from the apparatus after the test.

Result

The final report should include complete specifications of the material to be tested. Some identifications to be reported are the material designation, manufacturing process, fiber volume fraction, and void content. The load-displacement curves indicating load, displacement, and critical points must be observed. Susceptibility to delamination is one of the significant weaknesses of even advanced and high-end laminated composite structures. Thus, the final results are helpful in material selection and the product development phase.