ABSTRACT
In laminated composites used for aerospace structures, delaminations often occur by the impact under low and high velocities. Especially for the application of laminated composites to components of aeronautical turbo engines, the impact damage resistance is the primary design issue. Morita et al. [1] reported the damage resistance of CF/PEEK and CF/Toughened Epoxy laminates under low and high velocity impact tests. The report clarified that the relation between damage area (DA) and impact energy (IE) was linear, and the ratio DA/IE indicated the impact resistance for each specimen. Moreover, they reported that a ranking of impact resistance could be obtained both relatively and quantitatively among material systems tested in the work, and the ranking was dependent on impact velocity level. Masters [2] investigated the correlation of Compression After impact (CAI) strength and Mode II interlaminar fracture toughness in CFRP laminates. The work indicated that CAI strength could be estimated from Mode II interlaminar fracture toughness. However, the CAI strength is not usually used in designing of aeronautical turbo engines. It is desirable for the screening and selection of laminated composites in the designing to use a simple material property.
460In this reason, investigated in this study was the correlation of the damage resistance under low velocity impact and Mode II interlaminar fracture toughness in CFRP laminates. Three material systems, T800/3631 (CF/Epoxy), UT500/PEEK (CF/PEEK) and AS4/PEEK (CF/PEEK), were evaluated. This work consisted of three steps. The first step was to measure the damage resistance under low velocity impact of these material systems. The second step was to measure Mode II interlaminar fracture toughness of the laminates by conducting the End Notched Flexure (ENF) test. And the final step was to correlate the results obtained from low velocity impact tests and ENF tests.
