Specimen NameOpen-Hole Compressive

Strength

1st 278.2 MPa

2nd 273.0 MPa

Mean 275.6 MPa

ApplicationNews

No.i256

Material Testing System

Open-Hole Compression Test of Composite Material

LAAN-A-AG-E020

IntroductionCarbon fiber reinforced plastic (CFRP) has gained attention due to their strength and low weight, and have quickly been adopted for use in aeronautics and astronautics. CFRP has excellent strength characteristics in terms of specific strength and high rigidity, but lose much of their strength when a cutout is made. Consequently, composite materials used in aeroplanes must be evaluated by tests that use specimens with a hole cut out of their center. We performed open-hole compression testing of a CFRP according to ASTM D6484.

Measurement SystemThe CFRP spec imen used was T800S/3900. As shown in Fig. 1, a hole was created in the middle of the spec imen. ASTM D6484 descr ibes tes t methods in both SI and Imperial units, where the dimensions of the j igs and specimens differ in each. We performed testing with Imperial units. Specimen information is shown in Table 1.ASTM D6484 inc ludes two load ing methods , which are described as Method A and Method B. In Method A, the specimen and test f ixture are clamped in a gripping device, and the specimen is compressed by shear force applied by the fixture and gripping device. In Method B, compression plate is present at the ends of the specimen and fixture, and are used to compress the specimen. Method B was used, as shown in Fig. 2. Table 2 shows a l ist of the equipment used and Table 3 shows the test conditions used.

Length : 30 mmWidth : 38.1 mmThickness : 3.1 mmLamination Method : [45/0/–45/92] 2S

Table 1 Specimen Information

Fig. 1 Specimen

Fig. 2 Test Setup

Testing Machine : AG-XplusLoad Cell : 50 kNTest Fixture : Open-Hole Compression Test Fixture

Table 2 Experimental Equipment

Test Speed : 2 mm/min

Table 3 Test Conditions

ResultsMeasurements were performed twice. Test results are shown in Table 4 and stress-displacement curves are shown in Fig. 3. As shown in Table 4, the mean open-hole compressive strength was 275.6 MPa.

Table 4 Test Results

0020406080100120140160180200220240260280300

0.2 0.4 0.6 0.8 1 1.2Displacement (mm)

Stre

ss (N

/mm

2 )

1.4 1.6 1.8 2 2.2 2.5

ApplicationNews

No.

© Shimadzu Corporation, 2016

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i256

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Fig. 3 Stress-Displacement Curves

Results (DIC Analysis)Using the TRViewX non-contact extensometer allows for images and video of the specimen to be collected synchronized with test result col lect ion. Also, applying a random pattern of paint to the observed specimen surface allows the images or video to be used to determine the strain distribution on the observed specimen surface during the test by DIC analysis1). Open-hole compression testing and DIC ana lys i s were per formed us ing the spec imen described in Table 5. Fig. 4 shows a photograph of the open-hole compression test system with a non-c o n t a c t e x t e n s o m e t e r. F i g . 5 s h o w s s t r a i n distributions around the open hole in the specimen that were obtained by DIC analysis. Fig. 5 shows that strain accumulates at the vertical sides of the open hole (regions (1) and (3)), strain appears along the axis of compression from those points, and the final break occurs at the vert ica l s ides of the hole. Meanwhile, almost no strain appears in the central part of the hole (region (2)) throughout the test. This strain distribution probably occurred due to a 0˚ fiber orientation on the surface of the specimen.

Length : 30 mmWidth : 38 mmThickness : 1.6 mmLamination Method : [0/90] 2S

Table 5 Specimen Information (DIC)

1) DIC analysis is an analysis method that measures strain and showsthe strain distribution in a specimen based on movement of arandom pattern of paint applied to the observed specimen surfacebefore and during testing.

Fig. 4 Experimental Setup (DIC)

①②③

1 2 3

4 5 6

Fig. 5 DIC Analysis Results

ConclusionUsing this test system, open-hole compression testing of a CFRP was successfully performed according to ASTM D6484. Using a non-contact extensometer, we were also able to capture video (images) synchronized with the test force and crosshead displacement data obtained from the testing machine. Performing DIC analysis based on this video allowed an evaluation of the strain distribution on the observed specimen surface. This testing system will be extremely useful for the development of CFRPs and products that use CFRPs.

Edition: . 2016