Evaluation of porosity in composite aircraft structures

• Published in: Composites engineering 1993, Vol.3 (7), p.601,607-605,618
• Main Authors: Rubin, A.M., Jerina, K.L.
• Format: Article
• Language: English
• ISSN: 0961-9526
• DOI: 10.1016/0961-9526(93)90085-X

In recent years the use of carbon fiber-reinforced organic composite materials for highly loaded military and civil aircraft components has continuously increased. Because of these applications it is becoming even more important to be able to predict the material properties of composite laminates with different levels of material anomalies. One of the most common defects found in continuous carbon fiber composite laminate is porosity. The analytical techniques to determine porous laminate stiffness and residual strength are not available. Therefore, a variety of expensive and time-consuming structural tests have to be performed to include different laminate thickness and stacking sequence effects for each composite material. A new analytical approach to determine porous laminate stiffness for various levels of porosity which employs state of the art N.D.T. (nondestructive testing) techniques and photomicrographic examination to determine the porosity/voids distribution through the thickness of the laminate, and a thermomechanical constitutive theory for elastic composites with distributed damage is proposed, originally proposed by Allen et al. (1987a, b) Int. J. Solids Structs 23(9), 1301–1338. The model utilizes second-order tensor valued internal state variables to represent porosity. The equations for engineering constants are developed.