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Joosten M.W.,University of New South Wales | Dutton S.,University of New South Wales | Kelly D.,University of New South Wales | Thomson R.,Cooperative Research Center for Advanced Composite Structures
Composites Part A: Applied Science and Manufacturing | Year: 2010

An experimental evaluation of the energy absorption of constrained triggered sandwich structures is presented. Four configurations of embedded ply-drop triggering mechanisms were analysed and compared. A composite pi-joint was then developed to provide a constraint fixture that is representative of an in-service integrated energy absorbing structure. The specimens tested within the pi-joints obtained slightly lower specific energy absorption compared to the equivalent specimens tested in a rigid test fixture. The potential of an integrated energy absorbing triggered sandwich structure contained within a composite pi-joint was demonstrated. The interface between the sandwich panel and the pi-joint was not bonded, and further research will focus on the development of a bonded joint configuration suitable for structural applications. © 2010 Elsevier Ltd. All rights reserved. Source

Islam M.S.,University of Sydney | Islam M.S.,Cooperative Research Center for Advanced Composite Structures | Tong L.,University of Sydney
International Journal of Adhesion and Adhesives | Year: 2016

Installing and repairing of oil and gas infrastructure is required to be conducted out of water (OW) and in water (IW). In service, this infrastructure is subjected to various environmental ageing which may affect its mechanical performance. In this study the shear strength of metal-glass epoxy prepreg composites was investigated using single lap joint (SLJ) testing. For this, three different surface preparation methods (grit blasting, wire brushing and needle gunning) and two different manufacturing methods (OW and IW) were employed. Results showed that the specimens prepared by grit blasting had superior shear strength followed by these by needle gunning and wire brushed for both OW and IW methods. Manufactured specimens were also subjected to hygrothermal conditioning (WC) and ambient humidity conditioning (HC) to assess the durability of the produced SLJ specimens. The WC specimens absorbed more moisture than the HC specimens and the shear strength of the WC specimens were found to have deteriorated more than the HC specimens. For the conditioned SLJ specimens, the lower loss of shear strength was found with specimens manufactured IW when compared to specimens manufactured OW for grit blasted and needle gunned specimens and an opposite trend was seen for wire brushed specimens. However, the loss of shear strength was found to be varied with the moisture uptake for individual surface preparation technique and the variation was considered to be due to a combination of many factors other than the type of adhesive used such as metal surface profile, failure mode, rust formation and presence of black coloured metallic remnants. © 2016 Elsevier Ltd. Source

Joosten M.W.,University of New South Wales | Dutton S.,University of New South Wales | Kelly D.,University of New South Wales | Thomson R.,Cooperative Research Center for Advanced Composite Structures
Composite Structures | Year: 2011

The quasi-static crushing response of carbon epoxy composite hat-shaped crush elements is described herein. A steeple-type triggering mechanism was used to ensure the specimens exhibited a continuous stable crushing mode of failure. The explicit finite element software PAM-CRASH was used to predict the crushing failure of these energy absorbing elements. A four-layer, stacked-shell model of the composite hat-shaped element, after calibration against experimental test data, was found to be capable of closely approximating the failure modes and provide agreement with the load vs. displacement behaviour observed during the experiments. The predicted steady state load and specific energy absorption were respectively within 1.5 and 0.2% of the experimental average. With further validation, the developed stacked-shell methodology could help provide a predictive tool to characterise the energy absorption of open section crush elements and significantly reduce the cost associated with an extensive experimental material characterisation test program. © 2010 Elsevier Ltd. Source

Jackson A.,University of New South Wales | Dutton S.,University of New South Wales | Gunnion A.J.,Cooperative Research Center for Advanced Composite Structures | Kelly D.,University of New South Wales
Composite Structures | Year: 2011

The effect laminate design on the crush performance of carbon-fibre/epoxy "DLR" crush elements has been experimentally investigated. A quasi-isotropic lay-up was found to result in the highest Specific Energy Absorption (SEA) for Four-Harness (4HS) reinforced laminates; however a hybrid of unidirectional weave and 4HS fabric produced the highest SEA of 114 kJ/kg. Interleaving with thin thermoplastic films increased the steady state crushing force, however the increase in laminate density associated with the addition of the film caused no improvement and in some cases a reduction in SEA depending on material and lay-up. Dynamic crush testing of selected laminate designs resulted in a reduction in SEA of between 6% and 15% compared to the quasi-static case. © 2011 Elsevier Ltd. Source

Kim M.K.,RMIT University | Elder D.J.,Cooperative Research Center for Advanced Composite Structures | Wang C.H.,RMIT University | Feih S.,RMIT University
Composite Structures | Year: 2012

Impact tests were carried out on composite laminates and composite scarf repairs, while both were subjected to in-plane loading with tensile pre-strain levels up to 5000microstrain. The results show that pre-straining of the composite laminates has no noticeable influence on the size of the delamination area for the given impact energy of 8J, which represents a typical barely-visible impact on thin-skin composite structures. For composite scarf joints, however, resulting damage has been found to be a combination of adhesive disbonding and matrix cracking (delamination and intraply cracking) in the composite laminate. The size of this mixed type of damage increases significantly with increasing pre-strain levels. A finite element model was developed to investigate the interaction between adhesive disbonding and composite delamination. The computational results reveal that both delamination and adhesive disbonding are dominated by the mode II fracture. Since the critical mode II fracture energy release rate for composite laminates (G IIC=1.08kJ/m 2) is much less than that pertinent to the adhesive (G IIC=3.73kJ/m 2), delamination tends to occur first in the composite laminates, which then shield the growth of disbonding in the adhesive. © 2011 Elsevier Ltd. Source

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