1.1.This test method describes the experimental methods and procedures for the determination of the Mode I interlaminar fracture toughness of continuous fiber-reinforced ceramic matrix composite (CMC) materials in terms of the crack growth resistance (GIc). The test method is used to determine resistance-curve (R-curve) behavior for a CMC material by determining the initiation fracture toughness (initiation crack growth resistance -- GIc*) and any change in fracture toughness (GIc) as the crack propagates, showing R-curve behavior. The test method does not determine the fracture toughness in terms of the critical stress intensity factor (KIC), commonly used to quantify the fracture toughness of brittle ceramic materials. 1.2.The test method uses a double cantilever beam (DCB) test specimen (Fig. 1) which is a rectangular, laminated ceramic composite specimen of uniform thickness containing a starting notch/crack/delamina-tion in the center/starting plane that serves as a delamination crack initiator. Crack opening tensile forces are directly applied to the two opposing ends of the cantilever arms of the DCB specimen at ambient temperatures to extend the delamination crack in the center/starting plane. As the delamination crack grows, the applied force (P), the load point displacement (), and the delamination crack length/extension distances (a) are measured and recorded. The Mode I interlaminar fracture toughness (GIc --crack growth resistance) values for initiation and propagation are calculated from the applied force, the load point displacement, and the crack length/ extension distance, using a modified beam theory method or compliance calibration methods. 1.3.This test method applies primarily to ceramic matrix composite materials with a 2-D laminate structure, consisting of lay-ups of continuous ceramic fibers (in unidirectional tape or 2-D woven fabric architectures) within a brittle ceramic matrix.
Keywordsceramic matrix composite, interlaminar fracture toughness, crack growth resistance, double cantilever beam, delamination, Mode I
This new test standard is needed to determine the interlaminar fracture toughness (GIc --crack growth resistance) of laminated ceramic matrix composites at ambient temperature. It is based on the polymer matrix composite interlaminar fracture toughness standard test ( D5528) with modifications and additions to address the differences between ceramic matrix composites versus polymer matrix composites.
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
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