Composite materials are gradually replacing metals and other materials and are being used in almost all industries with a wide range of product streams. As the requirements for composite structures for aerospace, automobile, marine, and many other industries develop, the testing requirements for destructive testing (DT) and nondestructive testing (NDT) of composites also change. Improper manufacturing parameters and impact damage during service result in major defects in composite structures. Among the many defects that occur, voids are the most crucial in composite structures. Flaws have the potential to adversely affect performance, to the extent that the structure or component cannot operate under optimal service conditions. Nondestructive and destructive testing and inspection of composite structures for manufacturing and in-service damage detection have fueled the demand for a variety of techniques to assure quality during manufacturing and to detect flaws during service. In this study, composite panels with different porosity levels were subjected to nondestructive tests: ultrasonic testing (C-scan, A-scan), tap hammer, and visual inspection techniques. Destructive testing—burnout, acid digestion, ignition loss, and image void analysis techniques—was also employed to ascertain flaws in composite structures. The test parameters were analyzed and optimized in order to achieve maximum possible error data of voids, and a comparison was made between destructive and nondestructive testing methods. These studies indicated that the DT and NDT are extremely useful tools for the reliable and confident manufacturing of composite panels.