MILLIMETER-WAVE HEATING FOR THERMOGRAPHIC INSPECTION OF CARBON-FIBER-REINFORCED COMPOSITES

Thermography represents a useful in-service inspection technique for c arbon fiber-reinforced composite structures. Conventional heat loading by optical radiation suffers from dazzling the thermal imaging system and thermal artifacts possibly arising from variations in optical abs orptance of the paints used for coloring the structure. Microwave radi ation can overcome these disadvantages. It has been proved that the se lection Of millimeter wave frequencies gives sufficient heat to accomp lish one-sided thermographic testing irrespective of the (dielectric) coat of paint. Experimental results of the heating efficiency were sho wn for woven and multidirectional carbon fiber-reinforced epoxy lamina tes. Inspection performance was demonstrated by the detection of a bar ely visible impact damage.