Results of research of behavior of fiber threads are provided in case of the wave loads arising in samples in case of impact on them of cross explosive impulse effort. The considerable influence of nature of fixing of a cotton sample in captures of piezoelectric measuring systems is set. It is displayed by nature of registered wave pulses in examinees threads and shown samples levels of parameters of monitoring of properties of fibers in threads. The revealed distinctions are illustrated by data of cross-validation testing of cotton samples from aramide and polyethylene fibers. For all types of probed threads it is set that the free passing of wave pulse on a thread in a zone of measuring capture leads to the considerable change of a wave response of a sample in comparison with conditions of rigid fixing of the ends of a thread in captures. And it opens real opportunities to development of methods of optimization of structure and composition of multifilament threads for dynamic operating conditions. More profound analysis of an internal response of molecular structure of monofibers in case of pulse actions is carried out with attraction of the IR method – spectroscopies. Ranges of molecular structures of fibers of the SVM and Rusar, the threads excerpted from researched samples in the initial status and from the threads that have passed test for a cross gap are provided. The molecular segments most actively undergoing a radical response to excitation of molecular changes in structure of polymers are defined and marked.