FRP - Related Information

TRViewX Non-Contact Digital Video Extensometer -Example of Open Hole CFRP Plate Measurements

The V-notched beam testing method (Iosipescu method, ASTM D5379) is used widely in the field of composite materials for testing in-plane shear. This test method applies an asymmetrical four-point compression load to a sample with V-notches, which enables the application of only shear stress on the evaluation area.
This method can be used with various CFRP laminate materials, including unidirectional materials, orthogonally laminated materials, and materials with discontinuous fibers.

CFRPs have excellent characteristics in terms of specific strength and high rigidity, but they also lose a substantial amount of their strength when a cutout is made. In order to assess the use of composite materials for aircraft, tests must be performed with samples that have a circular hole cut through the center. ASTM D6468 is an open-Hole compression (OHC) testing method that uses a sample with a 6-mm (0.25-inch) diameter circular hole cut in its center.
ASTM D6468 has two loading methods: method A and method B. This video shows method B, in which the sample is compressed via compression plates located on the ends of the sample and jig.

Compressive strength is an extremely important property of composite materials for product design. A common compression test method is the combined loading compression (CLC) method (ASTM D6641).
The CLC method can be performed with a simple jig construction, using a long and narrow sample without tabs. It enables evaluating strength and measuring modulus of elasticity simultaneously.

Widely used methods of testing in-plane shear include the Iosipescu method (ASTM D5379), which applies an asymmetric four-point bending load to a notched sample, and a method (ISO 14129) that applies tensile loads at [+45/-45]ns.

The V-notched rail shear method (ASTM D7078) employed in this test uses a sample without holes with a large gauge section. It can also accommodate CFRPs with discontinuous fibers. This is an excellent method of in-plane shear testing as it allows for consistent tests.

The video illustrates the breakage of the CFRP by the high-speed tensile testing machine. The CFRP fractures instantaneously at the limit load, so a recording speed of 10 million frames/second is required to capture the fracturing process in detail.