Journal Published Online: 01 December 1984
Volume 6, Issue 4

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.

Author Information

Agarwal, BD
Indian Institute of Technology, Kanpur, India
Patro, BS
Indian Institute of Technology, Kanpur, India
Kumar, P
Indian Institute of Technology, Kanpur, India
Pages: 4
Price: $25.00
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Stock #: CTR10841J
ISSN: 0884-6804
DOI: 10.1520/CTR10841J