Showing papers by "Ajit Mal published in 1994"
TL;DR: In this article, the propagation of elastic waves in a composite containing randomly distributed parallel fibers is studied. And the effective phase velocity and attenuation of the coherent waves are calculated for a wide range of frequencies and concentrations.
Abstract: Propagation of elastic waves in a composite containing randomly distributed parallel fibers is studied in this paper. Both anti-plane (SH waves) and in-plane (P and SV waves) cases are considered. A multiple scattering theory and a statistical averaging procedure are implemented by means of the so-called Generalized Self Consistent Model (GSCM). Multiple scattering in the inhomogeneous medium results in a frequency dependent velocity and attenuation of the waves. The effective phase velocity and attenuation of the coherent waves are calculated for a wide range of frequencies and concentrations. The degree of interaction between the fibers is determined and the average strain calculated in a given inclusion by direct analysis and approximate homogenization is compared. The proposed method recovers three well-known static effective moduli of fiber-reinforced composites in the Rayleigh limit and the results at higher frequencies are physically reasonable.
107 citations
01 Aug 1994
TL;DR: In this article, the authors describe an ultrasonic testing system that yields data on elastic constants of matrix/fiber laminated composite material, which is performed nondestructive and involves access by ultrasonic probes to only one side of material specimen.
Abstract: Ultrasonic testing system yields data on elastic constants of matrix/fiber laminated composite material. Related to one described in "Ultrasonic System Measures Elastic Properties of Composites" (NPO-18729). Tests performed nondestructive, and involve access by ultrasonic probes to only one side of material specimen. In comparison with other available ultrasonic testing systems, this system relatively inexpensive, and based on testing technique that is simpler and rapidly yields more-accurate results.
5 citations
31 Jul 1994
TL;DR: In this paper, the degradation of the adhesive bonds is determined through comparison between experimental data and theoretical calculations using the leaky Lamb wave (LLW) experiment, which is a commonly used technique for measuring the thermal degradation of adhesive bonds in lap joints.
Abstract: The critical role played by adhesive bonds in lap joints is well known A good knowledge of the mechanical properties of adhesive bonds in lap joints is a prerequisite to the design and reliable prediction of the performance of these bonded structures Furthermore, the lap joint may be subject to high-temperature environments in service Early detection of the degree of thermal degradation in adhesive bonds is required under these circumstances A variety of ultrasonic nondestructive evaluation (NDE) techniques can be used to determine the thickness and the elastic moduli of adhesively bonded joints In this paper we apply a previously developed technique based on the leaky Lamb wave (LLW) experiment to investigate the possibility of characterizing the thermal degradation of adhesive bonds in lap joints The degradation of the adhesive bonds is determined through comparison between experimental data and theoretical calculations
1 citations
20 Feb 1994
TL;DR: The critical role played by adhesive bonds in the fracture and failure of composites and other bonded materials is well known and a good knowledge of the mechanical properties of these adhesion joints is a prerequisite to reliable design and reliable prediction of the performance of these bonded structures.
Abstract: The critical role played by adhesive bonds in the fracture and failure of composites and other bonded materials is well known. A good knowledge of the mechanical properties of these adhesion joints is a prerequisite to reliable design and reliable prediction of the performance of these bonded structures.
1 citations
01 Apr 1994
TL;DR: In this article, a device was developed to manipulate a pair of transmitting and receiving transducers at different angles of wave incidence and propagation with the fiber orientation to obtain reflected ultrasonic wave induced by oblique insonification of composite materials.
Abstract: The analysis of reflected ultrasonic waves induced by oblique insonification of composite materials is a powerful tool for providing informations about defects and material properties. A device was developed to manipulate a pair of transmitting and receiving transducers at vrious angles of wave incidence and propagation with the fiber orientation.