Low-Velocity Impact Resistance and Compression After Impact Strength of Thermoplastic Nanofiber Toughened Carbon/Epoxy Composites with Different Layups.

This study investigates the effectiveness of polyether block amide (PEBA) thermoplastic elastomeric nanofibers in reducing low-velocity impact damage across three carbon fiber composite lay-up configurations: a cross-ply [0°/90°]2s (CP) and a quasi-isotropic [0°/45°/90°/-45°]s (QI) lay-up utilizing unidirectional plies, and a stacked woven [(0°,90°)]4s (W) lay-up using twill woven fabric plies. The flexural strength and interlaminar shear strength of the composites remained unaffected by the addition of nanofibers: around 750 MPa and 63 MPa for CP, 550 MPa and 58 MPa for QI, and 650 MPa and 50 MPa for W, respectively. The incorporation of nanofibers in the interlaminar regions resulted in a substantial reduction in projected damage area, ranging from 30% to 50% reduction over an impact energy range of 5-20 J.

Permanent Deformation and Stiffness Degradation of Open Hole Glass/PA6 UD Thermoplastic Composite in Tension and Compression.

UD glass/PA6 coupons with an open hole are subjected to tensile and compressive loading. Three layups: [0/90], [+45/-45] and [+45/0/-45/90] with a shape based on ASTM D5766 were tested. Both monotonic loading as well as loading-unloading-reloading tests were executed.

Optimal Design Parameters for a Phased-Array-Based Ultrasonic Polar Scan.

In the context of designing a next-generation ultrasonic polar scan (UPS) measurement system for viscoelastic material characterization, a novel approach is proposed, which draws on a set of cylindrically focused emitters in conjunction with a circular phased array (C-PA) receiver in order to create a portable measurement system while improving the data quality and ease the data interpretation. To explore the potential of the new approach and determine its optimal design parameters, a 3-D analytical model is presented to numerically simulate UPS experiments with the proposed system. Furthermore, a postprocessing procedure is worked out to treat the acquired raw data with the aim to deal with the integrating effect of finite size transducers and directly reconstruct the angle-dependent plane wave reflection coefficients of the sample under study.

Parametric study on interply tracking in multilayer composites by analytic-signal technology.

Recently, researchers proposed the use of ultrasound combined with analytic-signal concepts for the reconstruction of the internal ply structure of composites. Optimal parameters for the pulse-echo mode ultrasonic testing are determined by modeling the analytic-signal response. The internal structure can be reconstructed by instantaneous metrics based on the interaction of the multilayer structure and the ultrasonic wave.

Numerical Study of a Phased Array-Based Ultrasonic Polar Scan to Determine Plane-Wave Reflection Coefficients of Plates.

Numerical finite-element (FE) simulations and postprocessing analysis methods are presented for ultrasonic polar scan (UPS) measurements involving a circular phased array (C-PA) to determine the plane-wave reflection coefficient of plates. Apodization weights for the C-PA elements are determined to assure the generation of a quasi-plane wave upon excitation at the plate surface and to mitigate bounded beam effects on the assessed reflection coefficient. In addition, postprocessing of the reflection signals is performed via the synthetic plane-wave technique to further filter out any bounded beam effects.

Attenuation estimation by repeatedly solving the forward scattering problem.

Estimation of the attenuation is important in medical ultrasound not only for correct time-gain compensation but also for tissue characterization. In this paper, the feasibility of a new method for attenuation estimation is tested. The proposed method estimates the attenuation by repeatedly solving the forward wave propagation problem and matching the simulated signals to the measured ones.

Temperature dependence of speed of sound and attenuation of porcine left ventricular myocardium.

The temperature dependence of soft tissue acoustic properties is relevant for monitoring tissue hyperthermia. In the current work, the propagation speed and attenuation of healthy porcine left ventricular myocardium (N=5) was investigated in a frequency range relevant for clinical diagnostic imaging, i.e.

Development of an ultrasonic shear reflection technique to monitor the crystallization of cocoa butter.

The quasi-isothermal crystallization process of cocoa butter was monitored by an ultrasonic shear reflection technique utilizing a custom-built experimental set-up in a temperature controlled environment. To facilitate the interpretation of the measurement results, the propagation of shear waves was first theoretically studied in different configurations of gas, liquid or solid layers with varying thickness for the case of normal incidence, yielding theoretical equations of the shear wave reflection coefficient (swRC) for different layering conditions. The typical experimentally observed pattern of the swRC during quasi-isothermal cocoa butter crystallization was subsequently linked to the theoretical equations.