Infrared thermography and thermoelastic stress analysis of composite materials and structural systems

Abstract

This study expands on the work of ElHajjar and HajAli (2003) on a quantitative thermoelastic strain analysis method for composite materials. Computational models for various prepreg and thicksection composites are validated with experiments using this quantitative strain analysis method. This study provides this thermomechanical calibrations for prepreg S2glass/epoxy, Carbon/epoxy, and pultruded Eglass/polyester. A research collaboration with the Institute of Paper Science and Technology (IPST) focused on infrared thermography for defect detection in wood and fibrous materials and structural systems. This study provides some detailed information on various testing setups for fiber and corrugated board systems to analyze anomalies and manufacturing defects. Quantitative infrared thermography is suggested as a preferred method for assessing the bond quality in corrugated paper systems. Methods for tracking fullfield thermal data during fatigue have been developed for FRP composites. The temperature changes on the surface of an FRP composite caused by damage during fatigue are tracked and thermoelastic stress analysis (TSA) technique is developed to relate the surface deformation to the IR emission. Infrared thermography is developed for fatigue damage detection in FRP composites with stochastic methods for analyzing this fullfield data. Future damage detection techniques in aging aircraft will require quantitative and noncontact nondestructive evaluation (NDE) methods especially for composite components. Infrared (IR) thermograpy techniques are qualitatively used to assess and indirectly infer the durability of structural systems. A research collaboration with Lockheed Martin for nondestructive evaluation of composite lap shear joints led to a development of thermoelastic stress analysis techniques for evaluation aerospace structures. Infrared thermography is used to investigate failure initiation and progression in composite lap shear joints.