Design and Operation of a Dual-Bridge Ultrasonic Inspection System for Composite Materials

The accepted method of inspecting composite aircraft and engine components is ultrasonic testing with a C-scan presentation of results. Within the last few years, analog recording systems have been superseded by digital data acquisition and analysis. Programmable control of mechanical scanning has improved upon earlier machines which could test only simple flat and circular shapes. The equipment described here was designed to inspect complex profiles such as aircraft engine vanes and ducts. A unique dual-bridge design with synchronized eleven-axis motion control was used to achieve this. The success of the system resulted from careful definition of initial design, and from the use of high-level software to supervise the otherwise lengthy task of programming complex scanning profiles

Fibre Distribution and the Process-Property Dilemma

The options for the fibre reinforcement of polymer matrix composites cover a range from short-fibre chopped strand mat, through woven fabric to unidirectional pre-impregnated (prepreg) reinforcements. The modelling of such materials may be simplified by assumptions such as perfect regular packing of fibres and the total absence of fibre waviness. However, these and other features such as the crimp or waviness in woven fabrics make real materials more complex than the simplified models. Clustering of fibres creates fibre-rich and resin-rich volumes (FRV and RRV respectively) in the composites. Prior to impregnation, large RRV will be pore-space that can expedite the flow of resin in liquid composite moulding processes (especially resin transfer moulding (RTM) and resin infusion under flexible tooling (RIFT). In the composite, the clustering of fibres tends to reduce the mechanical properties. The use of image processing and analysis can permit micro-/meso-structural characterisation which may correlate to the respective properties. This chapter considers the quantification of microstructure images in the context of the process-property dilemma for woven carbon-fibre reinforced composites with the aim of increasing understanding of the balance between processability and mechanical performance

Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials

An amendment to this paper has been published and can be accessed via the original article

To understand the expression profile and function of heparanase in the adult spinal cord

The presence of porosity in a structural material generally has a detrimental effect on the strength and mechanical properties of the component [1]. Excessive porosity is especially undesirable in laminated composites such as graphite-epoxy as it substantially degrades the interlaminar shear strength, the compressive strength and the transverse flexural strength, Detailed morphological knowledge of the pores such as their geometrical shape, orientation and location of occurrence in the laminate is valuable in several areas. In the nondestructive evaluation of porosity in composites using ultrasound, such morphological data will aid the model development of the interaction of the ultrasonic field with the voids and help the interpretation of the ultrasonic measurement results. In the investigation of the effects of defects, data on the pore morphology serve as inputs to models of the stress distribution around the defects and the interaction between the defects

Perceptual and Acoustic Predictors of Intelligibility and Acceptability in Dysarthria

The ultrasonic attenuation of a solid containing a distribution of voids depends on the number of voids per unit volume and the ultrasonic scattering cross-section of the voids. This physical picture has been shown to provide an accurate description of the attenuation behavior of ultrasound in metals containing low level porosity. For example, methods developed from this model for evaluating the average size and the volume fraction of porosity in cast aluminum have yielded good results [1]