In this paper we ultrasonic signals from array transducers are simulated using the Thompson and Gray measurement model. The measurement model consists of a beam model, a system efficiency factor which characterizes the response of the electro-mechanical and electrical components of the system, and a flaw scattering model. To inspect layered composite structures with complex geometries such as curvature, a beam model which is non-singular is required. Hence a multi Gaussian beam model for an ultrasonic array which includes the slowness surface parameters for unidirectional CFRP is investigated. The system functions of the ultrasonic array are modelled using a system efficiency model for a rectangular array. The Kirchoff approximation and separation of variables method for far field scattering in anisotropic materials is used to model the far field response of scatterers such as side drilled holes (SDH) in unidirectional CFRP. In summary the ultrasonic measurement model developed is able to predict the signals from scatterers such as side drilled holes (SDH) in transversely isotropic CFRP.

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This paper presents results of material characterisation experiments on the hygrothermal viscoelastic behaviour of unidirectional laminates of continuous carbon-fibre reinforced polyamide 6. The material behaviour when subjected to the automotive painting process is of interest. Coefficients of thermal- and -moisture expansion were determined from dilatometer experiments and micrometer measurements together with weighing, respectively. Diffusion coefficients were generated from thermogravimetric analysis and fitted with the Arrhenius equation. Dynamic mechanical analysis and digital image correlation of quasi-static tensile tests were performed to obtain a relaxation curve and a major Poisson's ratio, respectively. The Williams-Landel-Ferry equation was fitted to the time shift factors.

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Laser assisted automated tape or fiber placement (LATP/LAFP) with in-situ consolidation is a promising technique for manufacturing large structures, eliminating the limitations of autoclave curing. Currently, 2-D models are mostly preferred for the thermal analysis of the process. A 3-D, transient thermal finite element model is developed to analyze the effect of the alignment of the heat source with the tape laying direction and is compared with a model imitating a 2-D analysis space. This aspect of the process has not been considered in the literature so far. Effects of this aspect on temperature history and intimate contact evolution are presented.@en

Grid stiffened panels promise increased damage tolerance with reduced weight. Recent progress in automated manufacturing of composites has made it possible to produce such panels at low cost and thus has made them a competitive alternative to traditional skin-stiffened or sandwich panels. Fuselage skin panels typical of a 150 passenger aircraft were designed using an iterative process combining finite element models and local special purpose analysis methods. 40 cm by 30 cm panels, representing the final design, were fabricated using vacuum assisted resin transfer moulding. Pristine and impact damaged panels were tested in compression to failure. A progressive failure model was used to predict the extent and type of damage during impact. It was then combined with the global finite element model to obtain residual strength predictions. Analytical predictions were very close to test results. The fabrication method showed good quality and consistency and, when automated, can be used for production.

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Ultrasonic arrays are used for non-destructive evaluation of structures for aerospace and other applications. With the increase in the usage of fibre-reinforced composites in aerospace structures, this evaluation becomes complex due to the effects of attenuation and reflection from the layer boundaries in composite laminates. Hence there is considerable interest in developing beam models for accurate evaluation in such anisotropic media. In anisotropic media, the phase velocity varies with direction of propagation of the ultrasonic beam. Hence, the slowness surface and its properties play an important role in the beam models which are based on the paraxial approximation. The beam from a single element transducer is well collimated. However the beam from individual array elements is not well collimated and may affect the beam propagation through the composite structure. In this paper, Multi modular Gaussian beam (MMGB) model based on the paraxial approximation is applied to study the propagation of beam from an ultrasonic array in transversely isotropic fibre-reinforced composites. The effect of the slowness surface properties on the beam diffraction and skew through the composite structure are studied along with the influence of array parameters on the beam propagation through the structure. This work has demonstrated that the overall beam profile for quasi longitudinal beam from an ultrasonic array propagating in transversely isotropic fibre reinforced composites can be modelled as multi Gaussian beams. Simulation results are presented which illustrate the effects of? slowness properties on beam propagation in unidirectional CFRP in the symmetric planes.@en

The strict quality requirements for aerospace composite structures give rise to costly quality control procedures. In automated fibre placement (AFP) these procedures rely heavily on manual inspection leading to long machine downtime periods and a slower production process overall. A preventive non-destructive evaluation technique of the composite laminate quality based on an online geometric analysis of the fibre using a laser profile sensor has been developed. This sensor has been mounted on a KUKA KR210 R2700 Extra 10-axis robot and software integration was performed using Robot Operating System (ROS). The robot is equipped with interchangeable end-effectors including an automated fibre placement end-effector, developed at TU Delft. The robot mounted laser profile sensor, in combination with robot positional data, was used to create a 3D model of the fibre. This model can be used in two ways. In real-time it can be used to perform an online assessment of the laminate quality including layup geometry, positioning with respect to a reference location, and detection of in-plane buckling defects. Furthermore the full geometric model obtained can be used to validate mathematical or numerical simulations of the fibre placement process and investigate the effects of process variables on the quality of laminate placement and defect creation. In an industrial process this evaluation method can provide full traceability of the part-product quality. The data can both be used during the qualification of a newly designed laminate, but also for quality assurance during series production.@en

The strict quality requirements for aerospace composite struc- tures give rise to costly quality control procedures. In automated bre placement (AFP) these procedures rely heavily on manual work and inspection. This research aims at performing preventative non-destructive evaluation of composite laminate quality based on an online geometric analysis of the placed bre. A robot mounted laser pro le sensor, in combination with robot positional data, is used to create a 3D model of the bre. These are fused using quaternion coordinate transfer operations with the Robot Operat- ing System, an open source robotics platform. The 3D model is converted into an image for fast processing using open source algorithms from OpenCV. Deviations in part-product quality are identi ed in real-time including geometric, positioning and buckling defects due to high-radius curvatures in the bre path. Currently the prototype system will give a non-conformance warn- ing to the operator, and in future work it is planned to develop @en