Search

This paper helps to highlight the impact of tensile fatigue and hydric aging in sea water on a composite based the on aramid taffeta fibers and epoxy resin under acoustic monitoring. For this purpose, laminated test pieces were first stimulated to fatigue in several numbers of cycles (cycles 100-50000) before being immersed in the second place for several times (100 to 1000 h) in sea water (37%). The acoustic monitoring was conducted by three piezoelectric sensors were placed on the surfaces of the specimens during static tests. It allowed us to detect directly the different types of damage caused by fatigue and aging (matrix cracking, delamination and fiber breakage). The results that highlight the effects of fatigue and aging, show that these two parameters reduce the fracture characteristics of the material based on the progressively increasing number of cycles and increase the durations of immersions. [ABSTRACT FROM AUTHOR]

We present on this paper an experimental study of the follow-up of the damage of two laminate composites manufactured by RTM during their loadings in 3 points bending in static and cyclic tests. These materials are composed E glass fibres and epoxy resin. The mechanical tests are carried out on a standard hydraulic machine INSTRON 8516 that can be used in static and fatigue tests. The machine is interfaced whith a detected computer for controlling and data acquisition. The evolution of the damage is followed by acoustic emission using the system EPA NCV-2 connected to the testing machine, then confirmed by optical microscopic observations. The results obtained show that the curves of mechanical behaviour are strictly related to the observed damages. In the case of cyclic bending, the increase in the number of cycles involves a modulus reduction for the two materials that in loading as well as in unloading. The Acoustic emission allows to locate the mechanisms of damage and rupture caused by the loading of these materials. [ABSTRACT FROM AUTHOR]

The nature of changes in the parameters of acoustic emission (AE) was examined for a variety of structural materials under fatigue tests. The analysis of the behavior of AE suggests it is reflecting the main regularities of the failure process. In particular, depending on changes in the parameters of AE, was made the suggestion allocate the destruction conditions as follows: "fragile", "plastic", and "fragile-ductile". An analysis for possibilities of the predestruction criteria for different types of fatigue failures was made. [ABSTRACT FROM AUTHOR]

In this article are being presented the results of research on composite materials (CM) mechanical properties. The samples are of anisotropic reinforced plastics. Their shapes are conventional plates in shape of a cruciform and Maltese cross made for static - shear tests. The test program intended constant loading until complete destruction at the sample. The test procedures have enabled evaluation of levels of CM fibers and matrix failure by means of registration of acoustic emission (AE) signals parameters. [ABSTRACT FROM AUTHOR]

This research project developed an adaptive chip control system for rough turning. Continuous chips are detected with the help of acoustic emission signals during machining. The system monitors the breaking of chips, estimates the length of the chips and eliminates continuous chips if those are formed by stopping the feed and then restarting it at a higher rate. The control mechanism is based on communication between the software and the lathe knob. The system was tested with two combinations of cutting tools and work piece material. In the future, the chip control system should also be tested with more tools and materials. The system still requires development, e.g. to shorten the reaction time and simplify the sensors. The chip control capacity of the system created in this study is an important step towards improving unmanned production. [ABSTRACT FROM AUTHOR]