Nondestructive detection of damage in carbon fibre composites by SQUID magnetometry

Abstract

Monitoring of structural integrity is an essential issue in enhancing the affordability as well the safety of modern aircraft and spacecraft structures. Increasingly, metallic parts of aircrafts are being replaced by carbon fibre composite components due to their high strength and stiffness combined with low density. This paper reviews of the use of superconducting quantum interference devices (SQUIDs) in the detection of different types of damage in carbon fibre panels. The results presented here on impact damage on carbon fibre reinforced polymer and cracks induced by tensile loads on carbon fibre reinforced carbon matrix show that this method is sensitive not only to the presence but also the severity of damage. Indeed, it enables one to distinguish between the different failure mechanisms as the damage process evolves. SQUIDs response to artificial delaminations, flaws and deep-lying defects are also presented. The application of a neural network system for the detection of impact damage in a noisy environment is discussed. Experimental results demonstrate that nondestructive evaluation using SQUID magnetometers is a suitable technique to investigate composites to improve their mechanical properties

Identification of the local stiffness reduction of a damaged composite plate using the virtual fields method

“…Various non-destructive testing (NDT) methods have been developed to detect damage in composite laminates [52,59,110]. All the techniques have their own advantages and disadvantages.…”

“…Basically, once a structural component is delaminated, the component loses interlaminar shear carrying capability [59]. If the location of delamination is closer to the mid-plane of the member, the loss of interlaminar shear carrying ability increases.…”

“…Thermography utilizes thermal conductivity and emissivity of a specimen [52,59]. The specimen emits infrared radiation depending on its temperature and this radiated energy is recorded into thermal images.…”