Experimental impact damage resistance and tolerance study of symmetrical and unsymmetrical composite sandwich panels

This thesis presents the work of an experimental investigation into the impact damage resistance and damage tolerance for symmetrical and unsymmetrical composite honeycomb sandwich panels through in-plane compression. The primary aim of this research is to examine the impact damage resistance of various types of primarily carbon/epoxy skinned sandwich panels with varying skin thickness, skin lay-up, skin material, sandwich asymmetry and core density and investigate the residual in-plane compressive strengths of these panels with a specific focus on how the core of the sandwich contributes to the in-plane compressive behaviour. This aim is supported by four specifically constructed preconditions introduced into panels to provide an additional physical insight into the loading-bearing compression mechanisms. Impact damage was introduced into the panels over a range of IKEs via an instrumented drop-weight impact test rig with a hemi-spherical nosed impactor. The damage resistance in terms of the onset and propagation of various dominant damage mechanisms was characterised using damage extent in both impacted skin and core, absorbed energy and dent depth. Primary damage mechanisms were found to be impacted skin delamination and core crushing, regardless of skin and core combinations and at high energies, the impacted skin was fractured. In rare cases, interfacial skin/core debonding was found to occur. Significant increases in damage resistance were observed when skin thickness and core density were increased. The reduction trends of the residual in-plane compressive strengths of all the panels were evaluated using IKE, delamination and crushed core extents and dent depth. The majority of impact damaged panels were found to fail in the mid-section and suffered an initial decline in their residual compressive strengths. Thicker skinned and higher density core panels maintained their residual strength over a larger impact energy range. Final CAI strength reductions were observed in all panels when fibre fracture in the impacted skin was present after impact. Thinner skinned panels had a greater compressive strength over the thicker skinned panels, and panel asymmetry in thin symmetrical panels appeared to result in an improving damage tolerance trend as IKE was increased due to that the impact damage balanced the in-plane compressive resistance in the skins with respect to the pre-existing neutral plane shift due to the uneven skin thickness

Damping of flexural vibrations in glass fibre composite plates and honeycomb sandwich panels containing indentations of power-law profile

In this paper, the results of the experimental investigation into the addition of indentations of power-law profile into composite plates and panels and their subsequent inclusion into composite honeycomb sandwich panels are reported. The composite plates in question are sheets of composite with visible indentations of power-law profile. A panel is a sheet of composite with the indentations encased within the sample. This makes a panel similar in surface texture to an un-machined composite sheet (reference plate) or conventional honeycomb sandwich panel. In the case of quadratic or higher-order profiles, the above-mentioned indentations act as two-dimensional acoustic black holes (ABH) for flexural waves that can absorb a large proportion of the incident wave energy. For all the composite samples tested in this investigation, the addition of two-dimensional acoustic black holes resulted in further increase in damping of resonant vibrations, in addition to the already substantial inherent damping due to large values of the loss factor for composites. Due to large values of the loss factor for composite materials, there was no need to use attached absorbing layers to implement the acoustic black hole effect

Experimental study of impact damage resistance and tolerance of composite sandwich panels

An experimental study of in-plane compressive behaviour of carbon/epoxy-skinned and E-glass/epoxy-skinned sandwich panels was conducted. For the former, two carbon/epoxy skin thickness combinations were 8/6 plies and 16/12 plies. Both cross ply (CP) and quasi-isotropic (QI) lay-ups were used in each combination. For the latter, two E-glass/epoxy skin thickness combinations of 8/8 and 16/16 plies were used with both being in a cross ply lay-up. The majority of sandwich panels were impact-damaged with their dominant damage mechanisms being characterised. All impact-damaged and baseline panels were in-plane compression tested. The effects of impact damage, lacking symmetry, skin thickness, skin lay-up and core density on CAI strength were examined

Double Beam Shear (DBS) – a new test method for determining interlaminar shear properties of composite laminates

A new test method, the Double Beam Shear (DBS), has been developed at Loughborough University for the determination of the interlaminar shear (ILS) mechanical properties of fibre-reinforced laminated composite materials. The DBS uses an intact beam specimen with three equal-spaced supports under two loaders in such a way that each loader is applied at the middle of two supports. Under such set-up, two longitudinal pure ILS sections are induced in the two inner regions where the corresponding bending stresses are zero. It has been validated extensively using various composite laminates including carbon and E-glass fibre reinforcements, each in more than one thickness. The overwhelming majority of the tested specimens failed consistently in one of the inner regions with interior delamination. The magnitudes of the obtained ILS strengths of the composite materials are significantly greater than the corresponding apparent ILS strengths produced by the Short Beam Method. The DBS is especially able to induce ILS failure in certain composite materials, in which the Short Beam Method is not able to. The DBS Method is simple and easy to use

Double beam shear (DBS) as a new test method for determining interlaminar shear properties of composite laminates

We have developed a new test method, the DBS, at Loughborough University for determining interlaminar shear (ILS) properties in a single test. Overcoming the shortcomings of SBS and Iosipescu standards, the DBS method guarantees ILS failure at one of two pure ILS sections by promoting the dominance of ILS stresses. Extensive experimental validations of the DBS have been conducted along with SBS, using different types of composite material systems, involving different lay-ups. DBS ILS strengths are accurate, reliable and significantly greater in magnitude than SBS values. In particular, the DBS method is able to produce ILS failure in some composite laminates, which are unable to fail in delamination, using the SBS standard

Double Beam Shear (DBS) – a new test method for determining interlaminar shear properties of composite laminates

A new test method, the Double Beam Shear (DBS), has been developed at Loughborough University for the determination of the interlaminar shear (ILS) mechanical properties of fibre-reinforced laminated composite materials. The DBS uses an intact beam specimen with three equal-spaced supports under two loaders in such a way that each loader is applied at the middle of two supports. Under such set-up, two longitudinal pure ILS sections are induced in the two inner regions where the corresponding bending stresses are zero. It has been validated extensively using various composite laminates including carbon and E-glass fibre reinforcements, each in more than one thickness. The overwhelming majority of the tested specimens failed consistently in one of the inner regions with interior delamination. The magnitudes of the obtained ILS strengths of the composite materials are significantly greater than the corresponding apparent ILS strengths produced by the Short Beam Method. The DBS is especially able to induce ILS failure in certain composite materials, in which the Short Beam Method is not able to. The DBS Method is simple and easy to use

Damping of flexural vibrations in glass fibre composite plates and honeycomb sandwich panels containing indentations of power-law profile

In this paper, the results of the experimental investigation into the addition of indentations of power-law profile into composite plates and panels and their subsequent inclusion into composite honeycomb sandwich panels are reported. The composite plates in question are sheets of composite with visible indentations of power-law profile. A panel is a sheet of composite with the indentations encased within the sample. This makes a panel similar in surface texture to an un-machined composite sheet (reference plate) or conventional honeycomb sandwich panel. In the case of quadratic or higher-order profiles, the above-mentioned indentations act as two-dimensional acoustic black holes (ABH) for flexural waves that can absorb a large proportion of the incident wave energy. For all the composite samples tested in this investigation, the addition of two-dimensional acoustic black holes resulted in further increase in damping of resonant vibrations, in addition to the already substantial inherent damping due to large values of the loss factor for composites. Due to large values of the loss factor for composite materials, there was no need to use attached absorbing layers to implement the acoustic black hole effect

Randomized Crossover Comparison of Injection Site Pain with 40 mg/0.4 or 0.8 mL Formulations of Adalimumab in Patients with Rheumatoid Arthritis

<p><b>Article full text</b></p> <p><br></p> <p>The full text of this article can be found here<b>. </b><a href="https://link.springer.com/article/10.1007/s40744-016-0041-3">https://link.springer.com/article/10.1007/s40744-016-0041-3</a></p><p></p> <p><br></p> <p><b>Provide enhanced content for this article</b></p> <p><br></p> <p>If you are an author of this publication and would like to provide additional enhanced content for your article then please contact <a href="http://www.medengine.com/Redeem/”mailto:[email protected]”"><b>[email protected]</b></a>.</p> <p><br></p> <p>The journal offers a range of additional features designed to increase visibility and readership. All features will be thoroughly peer reviewed to ensure the content is of the highest scientific standard and all features are marked as ‘peer reviewed’ to ensure readers are aware that the content has been reviewed to the same level as the articles they are being presented alongside. Moreover, all sponsorship and disclosure information is included to provide complete transparency and adherence to good publication practices. This ensures that however the content is reached the reader has a full understanding of its origin. No fees are charged for hosting additional open access content.</p> <p><br></p> <p>Other enhanced features include, but are not limited to:</p> <p><br></p> <p>• Slide decks</p> <p>• Videos and animations</p> <p>• Audio abstracts</p> <p>• Audio slides</p

Patient and Healthcare Professionals Preference for Brenzys vs. Enbrel Autoinjector for Rheumatoid Arthritis: A Randomized Crossover Simulated-Use Study

<p><strong>Article full text</strong></p> <p><br> The full text of this article can be found <a href="https://link.springer.com/article/10.1007/s12325-017-0523-x"><b>here</b>.</a><br> <br> <strong>Provide enhanced digital features for this article</strong><br> If you are an author of this publication and would like to provide additional enhanced digital features for your article then please contact <u>[email protected]</u>.<br> <br> The journal offers a range of additional features designed to increase visibility and readership. All features will be thoroughly peer reviewed to ensure the content is of the highest scientific standard and all features are marked as ‘peer reviewed’ to ensure readers are aware that the content has been reviewed to the same level as the articles they are being presented alongside. Moreover, all sponsorship and disclosure information is included to provide complete transparency and adherence to good publication practices. This ensures that however the content is reached the reader has a full understanding of its origin. No fees are charged for hosting additional open access content.<br> <br> Other enhanced features include, but are not limited to:<br> • Slide decks<br> • Videos and animations<br> • Audio abstracts<br> • Audio slides<u></u></p

Stirred suspension bioreactors offered no growth improvement compared to static cultures.

<p>Fold expansion of β-TC6 spheroids after twenty one days compared stirred suspension bioreactor to static culture using standard high glucose medium.</p