Evaluation of Damage Tolerance under Mode II Deformation of Composite Structure for Tilting Train Carbody

II II II II

Damage tolerance under Mode II deformation of carbon fabric/epoxy composite, which was

applicable to a tilting train carbody, was investigated by a Mode II interlaminar fracture test. The

specimens were made of plain woven fabric with epoxy and a delamination at one end was made

by inserting Teflon film with the thickness of 12.5 or 25.0 . The equation for mode II

interlaminar fracture toughness was suggested based on the effective crack length from the

compliance of load-displacement curve. Mode II interlaminar fracture behaviors were investigated

through an optical travelling scope and a scanning electron microscope.

120

20

35

(unit : mm)

4.2

Fig. 1 Configuration of Mode II interlaminar fracture

specimen Fig. 2 Test set-up for evaluating Mode II interlaminar

fracture toughness

(1)

(2)

(3)

δ (4)

δ

(5)

δ (6)

δ

CF3327/Epoxy_12.5

Displacement (mm)

0 1 2 3 4 5

Load (N)

0 300 600 900 1200 1500

NL 5% offset NL

5% offset

①

①

①

①

②

② ②

②

③

③ ③

③

④

④ ④

④

⑤ ⑤ ⑤

⑤ ⑥ ⑥ ⑥ ⑥

Fig. 3 Several locations for investigating the crack propagating behaviors

Fig. 4 Microphotographs showing crack propagation on the edge of the specimen

Fig. 5 SEM photographs of fractured surfaces for the specimen with 12.5 thick inserter

Fig. 6 SEM photographs of fractured surfaces for the specimen with 25.0 thick inserter

NL 5% offset G

( J /m

)

0 500 1000 1500 2000 2500

12.5µm insert 25.0µm insert

Fig. 7 Comparison of mode II interlaminar fracture toughness

by varying with insert thickness