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In this research, three different techniques for melt impregnation of glass fiber bundles with polyamide 12 are assessed with the aim of creating a high strength and modulus material suitable for extrusion based additive manufacturing. Impregnation quality of three production techniques: 'Pultrusion', 'PassivePin', and 'ActivePin' were analyzed using three methods: matrix material mass fraction ([M.sub.m]) determination, scanning electron microscopy of composite fracture surfaces and optical microscopy of polished composite cross sections. Pultrusion material has an overall poor impregnation degree ([D.sub.i]) and fiber distribution and dispersion, the specimens lack mechanical strength and show fiber pull-out due to the excessive voids in the matrix. The PassivePin material has a significantly higher [D.sub.i] and a better fiber distribution, which results in less voids in the matrix and limited fiber pull-out. Finally, the ActivePin material scores significantly higher in [D.sub.i] and shows an excellent fiber distribution. As a consequence, very limited voids are observed and an even fracture surface without fiber pull-out is obtained. It is concluded that the ActivePin technique would be a great choice for application in an extrusion-based AM process, this method could allow for production of high strength and stiffness objects., INTRODUCTION Additive manufacturing (AM) and more specifically extrusion based fused deposition modeling is an interesting technique that has taken a giant leap forward during the last quarter-century. Despite its popularity, [...]

Electronic packages are multimaterial structures. Their reliability is a major concern for the electronic industry and therefore widely studied. Apart from the electrical performance, the mechanical stability also needs attention. A dreaded failure cause is delamination. Therefore it is interesting to have a modeling tool, which can provide information on possible delamination risks. In this paper, a short overview of existing appropriate analyzing techniques is presented, focusing on the fracture-mechanics approach. The implementation of the method using energy release rate components is discussed. However, as in all modeling applications, the need for 'critical material data' is also at hand. Therefore, the shear test is demonstrated to serve as a characterization tool The Si-BCB interface is applied as test-case. In order to obtain the critical material data for this interface, a set of experiments is designed and performed. Due to the brittle failure observed in the experiments, only information about the onset of the delamination is obtained, leading to a crack extension locus. By comparing the experimental results and the numerical finite element results, an estimation on this crack extension locus (in the [G.sub.1]-[G.sub.2] plane) can be made. This information can be used in later calculations on the reliability of components including Si-BCB interfaces. [DOI: 10.1115/1.4000209]

A numerical study based on finite element simulations which provide insight into leaky Rayleigh waves traversing along the horizontal surface of a thick fluid-loaded solid plate, transmitted around the corner of the solid plate is reported. The Rayleigh waves themselves are primarily physical origin of the transmission of Rayleigh waves rather than the scattering effects caused by the edge of an incident bounded beam.

To investigate monitoring of concrete members by integrating fiber optic technology, a series of static and dynamic loading tests have been conducted on a posttensioned concrete girder with a span of 16.8 m and a total depth of 0.8 m. For strain measurements optical fiber strain sensors, based on Bragg gratings, have been used. In literature only few papers deal with changes of dynamic parameters in posttensioned concrete at increasing damage levels. The obtained test results demonstrate the feasibility of fiber Bragg grating strain sensors, also for dynamic monitoring. On the dynamic behavior of the tested girder, it is found that, although a drop in eigenfrequencies is noticed with increasing load, significant shifts are only measured when the reinforcement starts yielding. Also with respect to damping values, no clear indication of damage in an early stage is observed. Further results show that the curvature of the mode shapes changes with increasing load and is related to the formation of a plastic hinge. An interesting observation is the change in phase angle between the modal strains and the vertical acceleration, which already occurred at an early stage. DOI: 10.1061/(ASCE)0733-9445(2007)133:4(541) CE Database subject headings: Concrete, prestressed; Girders; Sensors; Monitoring.

The interaction of complex harmonic plane waves on a periodically corrugated surface is described. It is shown that the ability of complex harmonic plane waves to stimulate leaky Rayleigh waves on a corrugated surface is similar to the ability of harmonic inhomogeneous waves to stimulate leaky Rayleigh waves on a smooth interface.

A historical survey of the development of the inhomogeneous wave theory, and its applications in the field of ultrasonic is illustrated. Several scientific features of inhomogeneous waves are described taking into account all topics of inhomogeneous wave research, such as viscoelastic solids and liquids, thermoviscous liquids and solids and anisotropic viscoelectric materials.

The history and the state of the art in radiation mode theory (RMT) in ultrasonics are described. The RMT originates from electromagnetism and has proved to be very efficient in describing the interaction of sound with discontinuities such a step on a plate, a liquid wedge, the extremity of a plate and much more.

A way to change the focal length of a single transducer without phased array technology and without changing the frequency is described. A study is performed for different beam shapes and for complex harmonic signals as well as for complex pulsed signals.

An overview of different techniques to characterize liquids in containers and the necessity of introducing a new technique based on the Schoch effect caused by Lamb wave stimulation in the skin of a container is given. It is shown that the Schoch effect can be used to distinguish between different liquids in containers.

A method is described for dealing with the diffraction of horizontally polarized shear incident plane waves at a corrugated interface between a solid and an ideal liquid. Creation of Love-like waves is predicted.