Design and analysis of grid stiffened concepts for aircraft composite primary structural applications

An approach to buckling resistant design of general grid stiffened flat plates based on smeared stiffener theory for combined inplane loading is discussed. Some results from parametric studies performed to assess the validity of smeared stiffener for practical stiffener configurations and to illustrate the benefits of different stiffening concepts are given. Details of a design study are discussed where the present analysis method is used to design a grid stiffened panel for a fuselage application and verified using a finite element analysis results

Design and evaluation of a foam-filled hat-stiffened panel concept for aircraft primary structural applications

Geodesically stiffened structures are very efficient in carrying combined bending, torsion, and pressure loading that is typical of primary aircraft structures. They are also very damage tolerant since there are multiple load paths available to redistribute loads compared to prismatically stiffened structures. Geodesically stiffened structures utilize continuous filament composite materials which make them amenable to automated manufacturing processes to reduce cost. The current practice for geodesically stiffened structures is to use a solid blade construction for the stiffener. This stiffener configuration is not an efficient concept and there is a need to identify other stiffener configurations that are more efficient but utilize the same manufacturing process as the solid blade. This paper describes a foam-filled stiffener cross section that is more efficient than a solid-blade stiffener in the load range corresponding to primary aircraft structures. A prismatic hat-stiffener panel design is then selected for structural evaluation in uni-axial compression with and without impact damage. Experimental results for both single stiffener specimens and multi-stiffener panel specimens are presented. Finite element analysis results are presented that predict the buckling and postbuckling response of the test specimens. Analytical results for both the element and panel specimens are compared with experimental results

Influence of transverse-shear and large-deformation effects on the low-speed impact response of laminated composite plates

An analytical procedure is presented for determining the transient response of simply supported, rectangular laminated composite plates subjected to impact loads from airgun-propelled or dropped-weight impactors. A first-order shear-deformation theory is included in the analysis to represent properly any local short-wave-length transient bending response. The impact force is modeled as a locally distributed load with a cosine-cosine distribution. A double Fourier series expansion and the Timoshenko small-increment method are used to determine the contact force, out-of-plane deflections, and in-plane strains and stresses at any plate location due to an impact force at any plate location. The results of experimental and analytical studies are compared for quasi-isotropic laminates. The results indicate that using the appropriate local force distribution for the locally loaded area and including transverse-shear-deformation effects in the laminated plate response analysis are important. The applicability of the present analytical procedure based on small deformation theory is investigated by comparing analytical and experimental results for combinations of quasi-isotropic laminate thicknesses and impact energy levels. The results of this study indicate that large-deformation effects influence the response of both 24- and 32-ply laminated plates, and that a geometrically nonlinear analysis is required for predicting the response accurately

Design and evaluation of a foam-filled hat-stiffened panel concept for aircraft primary structural applications

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as stiffener core has been designed for aircraft primary structural applications. This stiffener concept utilizes a manufacturing process that can be adapted readily to grid-stiffened structural configurations which possess inherent damage tolerance characteristics due to their multiplicity of load paths. The foam-filled hat-stiffener concept in a prismatically stiffened panel configuration is more efficient than most other stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The prismatically stiffened panel concept investigated here has been designed using AS4/3502 preimpregnated tape and Rohacell foam core and evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimens suggest that this structural concept responds to loading as anticipated and has good damage tolerance characteristics

Measurement of vortex flow fields

A 3-D laser fluorescence anemometer (LFA) was designed, built, and demonstrated for use in the Langley 16 x 24 inch Water Tunnel. Innovative optical design flexibility combined with compact and portable data acquisition and control systems were incorporated into the instrument. This will allow its use by NASA in other test facilities. A versatile fiber optic system facilities normal and off-axis laser beam alignment, removes mirror losses and improves laser safety. This added optical flexibility will also enable simple adaptation for use in the adjacent jet facility. New proprietary concepts in transmitting color separation, light collection, and novel prism separation of the scattered light was also designed and built into the system. Off-axis beam traverse and alignment complexity led to the requirement for a specialized, programmable transverse controller, and the inclusion of an additional traverse for the off-axis arm. To meet this challenge, an 'in-house' prototype unit was designed and built and traverse control software developed specifically for the water tunnel traverse applications. A specialized data acquisition interface was also required. This was designed and built for the LFA system

Damage tolerance of a geodesically stiffened advanced composite structural concept for aircraft structural applications

This paper describes the features of a geodesically stiffened panel concept that was designed for a fuselage application with a combined axial compression loading of 3,000 lb/in. and a shear loading of 600 lb/in. Specimens representative of this panel concept were tested in uniaxial compression both with and without low-speed impact damage to study the buckling and postbuckling response of the structure. Experimental results that describe the stiffness and failure characteristics of undamaged and impacted damage specimens are presented. A finite element analysis model that captures the principal details of the specimens was developed and used to predict the panel response. Analytical results on panel end-shortening are compared with the experimental results. Analytical results that describe panel end-shortening, out-of-plane displacement and stress resultants are presented

STRATEGI KOMUNIKASI PROGRAM RADIO LUMEN DALAM MENGHADAPI PERSAINGAN INDUSTRI SIARAN RADIO DI KABUPATEN MANGGARAI TENGAH PROVINSI NUSA TENGGARA TIMUR (NTT)

Radio sebagai salah satu media massa berfungsi sebagai sarana penyebaran informasi. Radio sebagai salah satu media massa berfungsi sebagai sarana penyebaran informasi. Selain memberikan informasi, radio juga bisa bermanfaat sebagai sarana pendidikan, dan hiburan di mana dapat digunakan untuk pengawasan masyarakat pada umumnya. Radio Lumens 2003 FM merupakan salah satu dari sekian banyak stasiun Radio yang masih beroperasi saat ini. Radio Lumens 2003 FM merupakan stasiun radio yang mengudara di provinsi Nusa Tenggara Timur. Oleh karena itu diperlukan sebuah strategi bagaimana radio Lumen 2003 bisa bertahan atau mempertahankan eksistensinya. Dalam mempertahankan pendengarnya, Radio Lumen 2003 melakukan strategi berupa Strategi Kesesuaian (compabillity), Membangun Kebiasaan (Habitt Formation), Mengontrol aliran pendengar, serta melakukan Strategi Pemeliharaan Sumber Daya Program serta Strategi daya tarik yang Luas (bredth of appreal). Radio Lumen FM selalu berusaha menyajikan program-program yang menarik untuk pendengarnya. Setiap program yang telah disiapkan selalu disajikan dengan semaksimal mungkin untuk menarik minat pendengar

Global behaviour of a composite stiffened panel in buckling. Part 2: Experimental investigation

The present study analyses an aircraft composite fuselage structure manufactured by the Liquid Resin Infusion (LRI) process and subjected to a compressive load. LRI is based on the moulding of high performance composite parts by infusing liquid resin on dry fibres instead of prepreg fabrics or Resin Transfer Moulding (RTM). Actual industrial projects face composite integrated structure issues as a number of structures (stiffeners, …) are more and more integrated onto the skins of aircraft fuselage. A post-buckling test of a composite fuselage representative panel is set up, from numerical results available in previous works. Two stereo Digital Image Correlation (DIC) systems are positioned on each side of the panel, that are aimed at correlating numerical and experimental out-of-plane displacements (corresponding to the skin local buckling displacements of the panel). First, the experimental approach and the test facility are presented. A post-mortem failure analysis is then performed with the help of Non-Destructive Techniques (NDT). X-ray Computed Tomography (CT) measurements and ultrasonic testing (US) techniques are able to explain the failure mechanisms that occured during this post-buckling test. Numerical results are validated by the experimental results

Compression Response of a Sandwich Fuselage Keel Panel With and Without Damage

Results are presented from an experimental and analytical study of a sandwich fuselage keel panel with and without damage. The fuselage keel panel is constructed of graphite-epoxy skins bonded to a honeycomb core, and is representative of a highly loaded fuselage keel structure. The face sheets of the panel contain several terminated or dropped plies along the length of the panel. The results presented provide a better understanding of the load distribution in damaged and undamaged thick-face-sheet composite sandwich structure with dropped plies and of the failure mechanisms of such structure in the presence of low-speed impact damage and discrete-source damage. The impact-damage condition studied corresponds to barely visible impact damage (BVID), and the discrete-source damage condition studied is a notch machined through both face sheets. Results are presented from an impact-damage screening study conducted on another panel of the same design to determine the impact energy necessary to inflict BVID on the panel. Results are presented from compression tests of the panel in three conditions: undamaged; BVID in two locations; and BVID in two locations and a notch through both face sheets. Surface strains in the face sheets of the undamaged panel and the notched panel obtained experimentally are compared with finite element analysis results. The experimental and analytical results suggest that for the damage conditions studied, discrete-source damage influences the structural performance more than BVID

Progressive Failure Modeling of Laminates Incorporating Material and Geometric Nonlinearities

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76951/1/AIAA-2006-1642-667.pd