|
Volume 6, Issue 4
(December 1984)
ISSN: 0884-6804
Prediction of Instability Point During Fracture of Composite Materials The crack growth resistance (R curve) approach [1,2] has been widely used to analyze fracture test results on composite materials [3–6]. The method requires measurement of instantaneous crack length with increasing load in a fracture test. In homogeneous materials, the crack is well defined and can be easily measured at any instant. However, fractures in composite materials proceed not by a simple enlargement of the original crack but by formation of a large number of microcracks due to debonding, matrix cracking, and fiber breaks. An instantaneous crack length is difficult to define or measure. Consequently, instantaneous crack length is estimated through a compliance matching procedure [7]. By applying this procedure, point by point, the complete load-crack opening displacement (COD) curve is transformed to an R curve. Fracture toughness of the composite is then obtained by locating the point of instability on the R curve. The process is tedious and time consuming and may reduce accuracy. This technical note mathematically establishes the point of instability on the load-COD curve, which eliminates the necessity of transforming the entire load-COD curve and thus saves time and increases accuracy in obtaining the fracture toughness.
Keywords:
Paper ID: CTR10841J | ||
