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Mölndal, Sweden

Olsson R.,Swerea SICOMP | Block T.B.,Faserinstitut Bremen e.V. | Block T.B.,Nordex Energy GmbH
Composite Structures | Year: 2015

Core shear cracking induced by impact on sandwich panels is a critical failure mode causing severe loss of structural performance. This paper reviews previous experimental and theoretical work in the area and derives improved closed form expressions for initiation of skin rupture and core shear cracking during impact on sandwich panels with foam cores. The criterion for skin rupture is also applicable to laminates without a core. It is shown that the skin rupture load limits the achievable core shear load, and that core shear cracking can be prevented by selecting a core thickness above a certain threshold value. The criteria are successfully validated by comparison with experimental results for a range of thicknesses of skins and cores in panels with carbon/epoxy skins and a Rohacell foam core. The criterion for skin rupture is also validated for plain laminates. © 2015 Elsevier Ltd. Source

Paajanen A.,VTT Technical Research Center of Finland | Korhonen T.,VTT Technical Research Center of Finland | Sippola M.,VTT Technical Research Center of Finland | Hostikka S.,VTT Technical Research Center of Finland | And 2 more authors.
Safety, Failures and Robustness of Large Structures | Year: 2013

Computational modelling of fire-structural response requires interoperability of various models describing different physical phenomena. Typically, the most advanced sub-models are found within independent simulation software incapable of interoperability. To address this issue, we have developed a tool for coupling two of such programs: Fire Dynamics Simulator and ABAQUS. We present the main features and theory behind the coupling approach and use an example case to demonstrate how a coupled fire-structural analysis is set up. We also discuss potential applications and present limitations of our approach. Source

Olsson R.,Swerea SICOMP
Composites Part A: Applied Science and Manufacturing | Year: 2015

This article presents analytical models for predicting large mass impact response and damage in thin-ply composite laminates. Existing models for large mass impact (quasi-static) response are presented and extended to account for damage phenomena observed in thin-ply composites. The most important addition is a set of criteria for initiation and growth of bending induced compressive fibre failure, which has been observed to be extensive in thin ply laminates, while it is rarely observed in conventional laminates. The model predictions are compared to results from previous tests on CFRP laminates with a plain weave made from thin spread tow bands. The experiments seem to confirm the model predictions, but also highlight the need to include the effects of widespread bending induced fibre failure into the structural model. © 2015 Elsevier Ltd. Source

Marklund E.,Lulea University of Technology | Asp L.E.,Lulea University of Technology | Olsson R.,Swerea SICOMP
Composites Part B: Engineering | Year: 2014

A multiscale approach is used to predict transverse tensile and transverse compressive strength of unidirectional non-crimp fabric (NCF) composites. Numerical analysis on fibre/matrix scale is performed to obtain the transverse strength of the fibre bundle to be further used in an analytical mesoscale model to predict the strength of the unidirectional NCF composite. Design of unidirectional layer composites with the same fibres, interface, matrix and volume fractions as in the bundle is suggested as an alternative method for bundle strength determination. Good agreement of both methods for bundle transverse strength determination is demonstrated. The simple analytical model used on mesoscale gives accurate predictions of the tensile transverse strength whereas the compressive strength is underestimated. The necessity of including bundle waviness in models when bidirectional NCF composites are analysed is demonstrated by FEM stress analysis and by experimental data showing differences in transverse cracking pattern due to bundle waviness. © 2014 Elsevier Ltd. All rights reserved. Source

Wagih A.,University of Girona | Wagih A.,Zagazig University | Maimi P.,University of Girona | Gonzalez E.V.,University of Girona | And 5 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2016

The study of the damage sequence in polymer-based composite laminates during an impact event is a difficult issue. The problem can be more complex when the plies are thin. In this paper, quasi-static indentation tests were conducted on thin-ply laminates to understand qualitatively the damage mechanisms and their sequence during low-velocity impact loading. TeXtreme® plain weave plies were used with two different thicknesses, 0.08 mm and 0.16 mm (referenced as ultra-thin-ply and thin-ply, respectively), and tested under different load levels. Load-displacement curves were analyzed and the extent of damage was inspected using optical microscopy and ultrasonic technique. The results showed that the damage onset occurs earlier in thin-ply laminates. The damage onset in thin-ply laminates is matrix cracking which induces delaminations, whereas for ultra-thin-ply laminates is due to delaminations which are induced by shear forces and small amount of matrix cracking. Moreover, the fiber breakage appears earlier in ultra-thin-ply laminates. © 2016 Elsevier Ltd. All rights reserved. Source

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