Sandwich Panel Cores for Blast Applications: Materials and Graded Density

Sandwich composites are of interest in marine applications due to their high strength-to-weight ratio and tailorable mechanical properties, but their resistance to air blast loading is not well understood. Full-scale 100 kg TNT equivalent air blast testing at a 15 m stand-off distance was performed on glass-fibre reinforced polymer (GFRP) sandwich panels with polyvinyl chloride (PVC); polymethacrylimid (PMI); and styrene acrylonitrile (SAN) foam cores, all possessing the same thickness and density. Further testing was performed to assess the blast resistance of a sandwich panel containing a stepwise graded density SAN foam core, increasing in density away from the blast facing side. Finally a sandwich panel containing compliant polypropylene (PP) fibres within the GFRP front face-sheet, was subjected to blast loading with the intention of preventing front face-sheet cracking during blast. Measurements of the sandwich panel responses were made using high-speed digital image correlation (DIC), and post-blast damage was assessed by sectioning the sandwich panels and mapping the damage observed. It was concluded that all cores are effective in improving blast tolerance and that the SAN core was the most blast tolerant out of the three foam polymer types, with the DIC results showing a lower deflection measured during blast, and post-blast visual inspections showing less damage suffered. By grading the density of the core it was found that through thickness crack propagation was mitigated, as well as damage in the higher density foam layers, thus resulting in a smoother back face-sheet deflection profile. By incorporating compliant PP fibres into the front face-sheet, cracking was prevented in the GFRP, despite damage being present in the core and the interfaces between the core and face-sheets

Shear coupling effects on stress and strain distributions in wood subjected to transverse compression

The mechanical behaviour of a wood board subjected to transverse compression is relevant to the performance of glulam beams and solid wood structures. The wood material can be described as polar orthotropic, due to the annual ring structure and to the differences in moduli in different directions in the radial-tangential plane. Strain measurements are performed on single wood boards using a whole-field digital speckle photography technique. Finite element analysis is performed and compared with experimental data. Good agreement in terms of strain fields and apparent moduli is observed between predictions and data. The experimental data show strong variations in local strain due to the polar orthotropic behaviour of wood in this plane, and the extremely low value for shear modulus G(rt) as compared with the other moduli. This leads to shear coupling effects resulting in large local shear deformation and correspondingly low effective stiffness under transverse global loading.</p

Preschool educational institution webpage

Pirmsskolas izglītības iestādes (PII) tīmekļa vietne ir tīmekļa vietne, kura paredz audzēkņu pievienošanu iestādes grupām, lietotāju saziņu un citu procesu funckionalitāti, ko var izlasīt sīkāk programmatūras prasību specifikācijā. Šī darba mērķis ir izstrādāt tīmekļa vietni pēc norādītās specifikācijas, papildināt esošās zināšanas, strādājot ar Laravel atvērtā koda PHP tīmekļa ietvaru, nostiprināt esošās ar phpMyAdmin tīmekļa pielikuma rīku un MySQL datubāziPreschool educational institution (PEI) webpage is a webpage, which provides student enrollment, user communication and other process functionalities, which can be read more in detail in the specification of software requirements. The aim of this work is to develop a webpage in accordance with the specification, to reinforce knowledge by wokring with Laravel in open source PHP framework, strengthen existing knowledge with phpMyAdmin web attachment tool and MySQL databas