Monitoring the Integrity of Composite Structures

A method is proposed to predict the future load response of structures made of composite materials. The method makes the predictions on the basis of past loadstrain data. The method was developed for structures subjected to monotonically increasing or to random cyclic tensile loads. A computer code PREDICT was written which, in real time, can provide predicted values of residual strengths and number of cycles to failure from measured data. Tests were performed to evaluate the validity of the method using specimens made of different materials, lay-ups, and geometries. The specimens were subjected to monotonically increasing or to cyclic tensile loads. During the tests, the residual strengths and number of cycles to failure were predicted, and were compared to the actual value generated in the tests. The predicted and measured values were in good agreement lending confidence to the method.