Crack-Tip Damage and Fracture Toughness of Boron/Aluminum Composites

Abstract

The fracture behavior of center notched unidirectional boron/aluminum composite under tensile loading has been investigated. Load-crack opening displacement (COD) curves were obtained for crack length-to-width ratios varying from 0.05 to 0.5. The COD was measured across the crack surfaces by means of the laser interferometric technique (gage length of 500 μm). As expected, the interferometric displacement gage (IDG) was found to be very sensitive to the appearance of damage at the crack tip, resulting in highly nonlinear load-COD curves. The damage at the crack-tip has been carefully examined by radiographs, SEM, photomicrographs, interfero metric miscroscope and optical interferometry technique. Fracture strength results and experimental load-COD curves were compared with analytical predictions and an excellent agreement has been established. The resistance curve method has also been tried and found to be non- applicable. An understanding of the correlation between the observed failure modes and deformation characteristics has been achieved.