Comparison of tensile strength and fracture toughness of co-bonded and cold-bonded carbon fiber laminate-aluminum adhesive joints

The purpose of this work is to compare the co-bonding vs. cold-bonding route on the adhesive joint performance of a CFRP (Carbon Fiber Reinforced Polymer) laminate–aluminum connection. In particular, the overlap shear, tensile strength and Mode I and Mode II fracture toughness will be evaluated. The adhesives for co-bonding and cold-bonding are, respectively, a thermosetting modified epoxy, unsupported structural film and a two-component epoxy adhesive, chosen as representative of applications in the high-performance/race car field. The emerging trend is that, in tensile e Mode I fracture tests, the failure path is predominantly in the composite. Mode II fracture tests instead resulted in a cohesive fracture, meaning that, under pure shear loading, the weakest link may not be the composite. The lap-shear tests are placed midway (cohesive failure for co-bonding and composite delamination for cold-bonding, respectively), probably due to the different peel stress values related to the different adhesive Young’s modulus. The exploitation of the full capacity of the adhesive joint, hence the possibility of highlighting better, different performances of co-bonding vs. cold-bonding, would require consistent improvement of the out-of-plane strength of the CFRP laminate and/or to someway redistribute the peel stress on the bondline

Geometrical Calibration for the Panrover: a Stereo Omnidirectional System for Planetary Rover

Abstract. A novel panoramic stereo imaging system is proposed in this paper. The system is able to carry out a 360° stereoscopic vision, useful for rover autonomous-driving, and capture simultaneously a high-resolution stereo scene. The core of the concept is a novel "bifocal panoramic lens" (BPL) based on hyper hemispheric model (Pernechele et al. 2016). This BPL is able to record a panoramic field of view (FoV) and, simultaneously, an area (belonging to the panoramic FoV) with a given degree of magnification by using a unique image sensor. This strategy makes possible to avoid rotational mechanisms. Using two BPLs settled in a vertical baseline (system called PANROVER) allows the monitoring of the surrounding environment in stereoscopic (3D) mode and, simultaneously, capturing an high-resolution stereoscopic images to analyse scientific cases, making it a new paradigm in the planetary rovers framework.Differently from the majority of the Mars systems which are based on rotational mechanisms for the acquisition of the panoramic images (mosaicked on ground), the PANROVER does not contain any moving components and can rescue a hi-rate stereo images of the context panorama.Scope of this work is the geometric calibration of the panoramic acquisition system by the omnidirectional calibration methods (Scaramuzza et al. 2006) based on Zhang calibration grid. The procedures are applied in order to obtain well rectified synchronized stereo images to be available for 3D reconstruction. We applied a Zhang chess boards based approach even during STC/SIMBIO-SYS stereo camera calibration (Simioni et al. 2014, 2017). In this case the target of the calibration will be the stereo heads (the BPLs) of the PANROVER with the scope of extracting the intrinsic parameters of the optical systems. Differently by previous pipelines, using the same data bench the estimate of the extrinsic parameters is performed

influence of material and manufacturing technology on the failure behavior of composite laminate bonded joints

Abstract The purpose of this work is to evaluate the influence of co-lamination vs. co-bonding on the failure behavior, and namely the fracture toughness, of carbon fibre reinforced (CFR) composite laminate joints in order to assess comparatively their performance. Since the strength of the laminate and ply texture are parameters affecting the strength of the joint, the comparison is extended to two different types of CFR pre-preg fibers, a satin T1100 with 2573 Nanoalloy® epoxy resin supplied by Toray and a twill T700 with ER450 toughened epoxy resin supplied by CIT, Toray group, representative of two different fields of application, racing and automotive, respectively

comparative investigation of mode i and ii fracture toughness of directly cured cfrp and co cured bonded cfrp joints

Abstract Adhesive bonding is the elective joining system between Carbon-Fiber Reinforced Polymer (CFRP) parts because, with respect to fastening, it allows a large connection area, no additional parts (hence weight saving) and no need to drill holes into the composite, that is always detrimental for the strength due to the possibility of developing damage. However, the choice of bonding CFRP should be evaluated as alternative to direct curing in terms of strength and durability, compared to cost and manufacturing time and complexity. In this work, a comparison between directly cured and co-cured, bonded CFRP is done with respect to mode I and mode II fracture toughness, in order to understand whether bonding guarantees the same performance of a co-cured composite part

Telecentric F-theta fisheye lens for space applications

A very wide angle lens with a field of view of 360°x180° - a fisheye lens - has been designed to be used in a space environment. As a case study, the lens is assumed to be mounted on a spinning probe passing through a comet’s tail. The lens, rotating with the probe passing through the comet coma, may map the entire sky as viewed from the interior tail, providing unprecedented data on the spatial distribution of plasma and dust. Considering the foreseen space applications for the lens, radiation hardened glass has been taken into account for the design. A key feature of the lens is the “angular scale” uniformity (F-theta) of the sky distribution map projected on the focal plane allowing to obtain a reliable whole sky reconstruction. Care has also been taken to obtain an almost telecentric design, in order to permit filters placed on the focal plane to work properly. A telecentric fisheye operating with a pixel-limited resolution in the waveband from 500 nm up to 770 nm and with an F-theta distortion is presented in this paper

Spatially-resolved spectrophotometric analysis and modelling of the Superantennae

We have performed spatially-resolved spectroscopy of the double-nucleated Ultra-Luminous Infrared Galaxy IRAS 19254-7245, ``the Superantennae'', along the line connecting the two nuclei. These data are analysed with a spectral synthesis code, to derive the star formation and extinction properties of the galaxy. The star formation history (SFH) of the two nuclei is similarly characterized by two different main episodes: a recent burst, responsible of the observed emission lines, and an older one, occurred roughly 1 Gyr ago. We tentatively associate this bimodal SFH with a double encounter in the dynamical history of the merger. We have complemented our study with a detailed analysis of the broad band spectral energy distribution of the Superantennae, built from published photometry, providing the separate optical-to-mm SEDs of the two nuclei. Our analysis shows that: a) the southern nucleus is responsible for about 80% of the total infrared luminosity of the system, b) the L-band luminosity in the southern nucleus is dominated by the emission from an obscured AGN, providing about 40 to 50% of the bolometric flux between 8 and 1000 microns; c) the northern nucleus does not show evidence for AGN emission and appears to be in a post-starburst phase. As for the relative strengths of the AGN and starburst components, we find that, while they are comparable at FIR and sub-mm wavelengths, in the radio the Sy2 emission dominates by an order of magnitude the starburst.Comment: 18 pages. Accepted for publication on A&

Polarimetric survey of asteroids with the Asiago telescope

We present the first results of an asteroid photo--polarimetry program started at Asiago--Cima Ekar Observatory. The aim of our survey is to estimate diversity in polarimetric properties of asteroids belonging to different taxonomic and dynamical classes. The data were obtained with the polarization analyser placed inside the Faint Object Spectrographic Camera (AFOSC) of the 1.8m telescope. This instrument allows simultaneous measurements of the two first Stokes parameters without any lambda/2 retarding plate. Our survey began in 2002, and up to now we have obtained data on a sample of 36 asteroids; most of them are being investigated with the polarimetric technique for the first time. Combining our data with those already available in literature, we present an estimate of the inversion angle for 7 asteroids in this paper. Furthermore, we present the polarimetric measurements of the rare asteroid classes belonging to the A and D types and a detailed VRI observations at extremely small phase angles of the low albedo asteroid 1021 Flammari

Space-to-ground quantum-communication using an optical ground station: a feasibility study

We have tested the experimental prerequisites for a Space-to-Ground quantum communication link between satellites and an optical ground station. The feasibility of our ideas is being assessed using the facilities of the ASI Matera Laser Ranging Observatory (MLRO). Specific emphasis is put on the necessary technological modifications of the existing infrastructure to achieve single photon reception from an orbiting satellite.Comment: 8 pages 5 figures, SPIE proceedings Quantum Communications and Quantum Imaging II conference in Denver, July 200