Analytical ultrasonics for evaluation of composite materials response. Part 2: Generation and detection

To evaluate the response of composite materials, it is imperative that the input excitation as well as the observed output be well characterized. This characterization ideally should be in terms of displacements as a function of time with high spatial resolution. Additionally, the ability to prescribe these features for the excitation is highly desirable. Various methods for generating and detecting ultrasound in advanced composite materials are examined. Characterization and tailoring of input excitation is considered for contact and noncontact, mechanical, and electromechanical devices. Type of response as well as temporal and spatial resolution of detection methods are discussed as well. Results of investigations at Virginia Tech in application of these techniques to characterizing the response of advanced composites are presented

Analytical ultrasonics for evaluation of composite materials response. Part 1: Physical interpretation

The phenomena associated with the propagation of elastic waves in anisotropic materials are discussed. Wave modes propagating in general directions relative to the material coordinate system are not purely longitudinal nor transverse. Hence the generation of ultrasonic waves by common piezoelectric transducers will generate multiple modes to some extent. The received signals will likely be a combination of different modes. When using two transducers to send and receive ultrasonic waves, deviation of the energy flux vector may reduce the apparent value of the received signal unless the proper orientation of the two transducers with respect to one another is taken into account. And application of reflection from plane boundaries for the purposes of making certain measurements may lead to misinterpretation of results unless one is aware of the differences in multiple mode generation and critical angle phenomena between isotropic and anisotropic materials. When studies or characterizations of composite materials by ultrasonics are to be performed, these phenomena must be taken into consideration so that proper and correct application and interpretation of the measurements can be made. Finally, attention must be drawn again to the fact that composite materials are heterogeneous by definition. The results discussed here have been determined for homogeneous materials only. While the assumption of homogeneity appears to be valid for certain wavelength ranges in composites, future work must continue to study the phenomena of wave propagation in anisotropic, nonhomogeneous materials

The compressive failure of graphite/epoxy plates with circular holes

The behavior of fiber reinforced composite plates containing a circular cutout was characterized in terms of geometry (thickness, width, hole diameter), and material properties (bending/extensional stiffness). Results were incorporated in a data base for use by designers in determining the ultimate strength of such a structure. Two thicknesses, 24 plies and 48 plies were chosen to differentiate between buckling and strength failures due to the presence of a cutout. Consistent post-buckling strength was exhibited by both laminate configurations

Ultrasonic stress wave characterization of composite materials

The work reported covers three simultaneous projects. The first project was concerned with: (1) establishing the sensitivity of the acousto-ultrasonic method for evaluating subtle forms of damage development in cyclically loaded composite materials, (2) establishing the ability of the acousto-ultrasonic method for detecting initial material imperfections that lead to localized damage growth and final specimen failure, and (3) characteristics of the NBS/Proctor sensor/receiver for acousto-ultrasonic evaluation of laminated composite materials. The second project was concerned with examining the nature of the wave propagation that occurs during acoustic-ultrasonic evaluation of composite laminates and demonstrating the role of Lamb or plate wave modes and their utilization for characterizing composite laminates. The third project was concerned with the replacement of contact-type receiving piezotransducers with noncontacting laser-optical sensors for acousto-ultrasonic signal acquisition

A study of the stress wave factor technique for nondestructive evaluation of composite materials

The acousto-ultrasonic method of nondestructive evaluation is an extremely sensitive means of assessing material response. Efforts continue to complete the understanding of this method. In order to achieve the full sensitivity of the technique, extreme care must be taken in its performance. This report provides an update of the efforts to advance the understanding of this method and to increase its application to the nondestructive evaluation of composite materials. Included are descriptions of a novel optical system that is capable of measuring in-plane and out-of-plane displacements, an IBM PC-based data acquisition system, an extensive data analysis software package, the azimuthal variation of acousto-ultrasonic behavior in graphite/epoxy laminates, and preliminary examination of processing variation in graphite-aluminum tubes

A study of the stress wave factor technique for evaluation of composite materials

The acousto-ultrasonic approach for nondestructive evaluation provides a measurement procedure for quantifying the integrated effect of globally distributed damage characteristic of fiber reinforced composite materials. The evaluation procedure provides a stress wave factor that correlates closely with several material performance parameters. The procedure was investigated for a variety of materials including advanced composites, hybrid structure bonds, adhesive bonds, wood products, and wire rope. The research program focused primarily on development of fundamental understanding and applications advancements of acousto-ultrasonics for materials characterization. This involves characterization of materials for which detection, location, and identification of imperfections cannot at present be analyzed satisfactorily with mechanical performance prediction models. In addition to presenting definitive studies on application potentials, the understanding of the acousto-ultrasonic method as applied to advanced composites is reviewed

Ultrasonic Inspection of Graphite-Epoxy Solid Rocket Motor Canisters

Thick filament-wound composite materials are particularly attractive for use in solid rocket motor structures. However, these materials are difficult to inspect because of the scattering losses associated with multiple fiber layers. Damage caused by either low or high velocity impact which results in matrix cracking, delaminations and broken fibers cannot be tolerated because of the possibility of catastrophic system failure. American Research Corporation of Virginia has performed a 2-year Phase II Small Business Innovation Research contract to develop an ultrasonic inspection system for graphite/epoxy rocket motor canisters [1]. This paper details the experimental apparatus and testing of rocket motor canisters, presents testing results and discusses observations and detection thresholds

Prospect of Sea Cucumber Culture in Indonesia as Potential Food Sources

Sea cucumber is one of the sea treasures which has been used not only as luxury food for certain countries but also as medicines. Sea cucumber has become one of the most important products and it has high price in International market.For this reason, the exploitation of sea cucumber turns out to be excessive and disturbs its sustainability. Aquaculture is the best way to prevent this problem. The success of sea cucumber culture is very depend on seed availability and suitable food for larvae as well as juvenile along with growing out stadia for market requirement

Utilization of life feed Alona sp., Boiled Egg Yolk and Commercial Feed Toward Survival Rate of Betta Fish Larvae

The purpose of this study was to find out the survival rates of betta fish larvae (cupang) that were given life feed Alona sp., boiled egg yolk and commercial feed for 21 days. Data analysis was performed by one-way ANOVA, and continued with BNJ (Tukey) test. The result of the survival rate is as follow treatment with life feed Alona sp. 56%, treatment with boiled egg yolk 26%, and treatment with commercial feed 0%. The results of statistical tests show there are significant differences.  Significant value p <.0002 (<.05). Water quality parameter measured during the study was temperature of 26 ºC.Keywords: betta fish larvae, life feed, Alona sp., survival rateABSTRAKTujuan penelitian ini adalah untuk mendapatkan laju kelangsungan hidup larva ikan betta (cupang) yang dibeerikan pakan alami Alona sp., rebusan kuning telur dan pakan komersil selama 21 hari.  Analisis data dilakukan dengan ANOVA one way, dan dilanjutkan dengan uji BNJ (Tukey).  Hasil laju kelangsungan hidup adalah sebagai berikut, perlakuan dengan pakan alami Alona sp. 56%, perlakuan dengan rebusan kuning telur 26%, dan perlakuan dengan pakan komersil 0%.  Hasil uji statistik menunjukan adanya perbedaan yang nyata.  Nilai signifikan p <.0002 (<.05).  Parameter kualitas air yang diukur selama penelitian adalah suhu 26ºC.Keywords: larva ikan betta, pakan alami, Alona sp., kelangsungan hidu

The Use of Fish Silage in Different Composition for the Growth of Carp Cyprinus Carpio L.

Penelitian ini bertujuan untuk menelaah pemberian silase ikan bagi pertumbuhan mutlak, pertumbuhan nisbi, dan pertumbuhan harian ikan mas (Cyprinus carpio L.), yang dipelihara dalam petak-petak jaring berukuran 1x 0,5 x 1 m, dengan padat penebaran 10 ekor ikan berukuran 3-5 cm. Rancangan percobaan yang digunakan adalah rancangan acak lengkap (RAL) dengan 4 perlakuan dan 3 ulangan; perlakuan A pelet berkomposisi silase ikan 10%, perlakuan B pelet berkomposisi silase ikan 20 %, perlakuan C pelet berkomposisi silase ikan 30 % dan perlakuan D adalah pelet komersil. Uji ANOVA menunjukkan bahwa pengaruh perlakuan di antara pakan A, B, C, dan D yang diujicobakan tidak memberikan perbedaan yang nyata terhadap pertumbuhan mutlak, pertumbuhan nisbi dan pertumbuhan harian benih ikan mas