Application of a Special X-Ray Nondestructive Testing Technique for Monitoring Damage Zone Growth in Composite Laminates

Abstract

A modified X-ray nondestructive testing technique was used to study matrix cracks parallel to fibers and delaminations between plies in graphite-epoxy composite material. A tetrabromoethane (TBE) opaque additive applied at the source of the damage zones enhanced the flaw image. Center-slit specimens were fabricated from Modmor II/Narmco 5208 graphite-epoxy laminates with three different ply orientations. Tensile ramp and sawtooth cyclic loadings at different levels were applied to these specimens. Periodic X-ray monitoring was conducted to observe the initiation and growth of cracks and delaminations at the slit tips. The initiation of damage zones appeared as fiber separation in the ±45-deg directions tangent to the semicircular periphery of the cutout tips. As the load level was increased, this fiber separation continued while fiber separation at other locations also appeared. Delamination first occurred at approximately the same time as fiber separation. The delaminated area was found to surround the most severe fiber separation region and grew in size as the load level was increased. Limited test results indicated a slow and an accelerated damage growth rate during ramp loading. For cyclic loading the majority of growth occurred on the first load cycle. Subsequent cyclic loading to the same level contributed little additional growth in the majority cases.

A multiresolution approach for damage detection in fiber-reinforced polymer pipe systems

“…Direct damage detection methods include, among others, X-ray, 3 gamma-ray radiography, 4 ultrasonic probes, laser ultrasound, 5,6 thermography, 7 and microwave electromagnetic imaging. 8 In addition, acoustic techniques such as low power impulse radar, acoustic emission, and elastic wave emitter-detector pairs are in use.…”

Modal frequencies of fiber-reinforced polymer pipes with wall-thinning using a wavelet-based finite element model

“…2 Several researchers have investigated the solid particle erosion behavior of polymer matrix composites and concluded that FRP material is prone to flow-induced wall-thinning due to erosion. [3][4][5][6] Various non-destructive evaluation (NDE) techniques have been studied to detect damage and cracks in composite materials such as X-ray 7 and gamma-ray radiography. 8 In addition, acoustic techniques such as ultrasonic probes, laser ultrasound, 9,10 low-power impulse radar, acoustic emission, and elastic wave emitter-detector pairs have been also used.…”

“…Moreover, thermography 11 and microwave electromagnetic imaging 12 have been employed to investigate the damage in composite structures. However, the available non-destructive testing (NDT) methods have difficulties associated with their application in the field, as reported for radiography-based techniques, 7,8 ultrasonic tomography 13 and for infrared thermography. 14 In addition, the available NDT methods have limitations with respect to area of coverage, large thickness, and interpretation of their measurements.…”

Improved interdigital sensors for structural health monitoring of composite retrofit systems

“…Radiography technique is one of the oldest NDE techniques. 1,2 Radiography is a photographic record produced by the penetration of electromagnetic radiation such as X-rays and gamma rays through the inspected object onto a film or other media. However, radiographic methods require large and costly equipment and extensive safety measures against radiation hazards.…”