X-ray CT Analysis after Blast of Composite Sandwich Panels

Four composite sandwich panels with either single density or graded density foam cores and different face-sheet materials were subjected to full-scale underwater blast testing. The panels were subjected to 1kg PE4 charge at a stand-off distance of 1 m. The panel with graded density core and carbon fiber face-sheets had the lowest deflection. Post-blast damage assessment was carried out using X-ray CT scanning. The damage assessment revealed that there is a trade-off between reduced panel deflection and panel damage. This research has been performed as part of a program sponsored by the Office of Naval Research (ONR)

The Comparison of Various Foam Polymer Types in Composite Sandwich Panels Subjected to Full Scale Air Blast Loading

Full scale air blast testing has been performed on a range of polymeric foam composite panels. These panels employed glass fibre reinforced polymer (GFRP) face-sheets with different polymer foam cores, namely: Styrene acrylonitrile (SAN); Polyvinylchloride (PVC) and Polymethacrylimide (PMI). The three sandwich panels were all subjected to 100 kg TNT equivalent blast loading at a stand-off distance of 15 m, and the responses of the panels were measured using Digital Image Correlation (DIC). The extent of damage in the sandwich panels was then inspected via post-blast sectioning, and it was found that the SAN core suffered the least damage, and the PMI suffered the most. The DIC showed that the deflection of the SAN core sandwich panel was much less than the other two foam polymer cores, due to less damage meaning a greater stiffness was retained. All blast research to date is part of a programme sponsored by the Office of Naval Research (ONR)

X-ray CT analysis after blast of composite sandwich panels

Four composite sandwich panels with either single density or graded density foam cores and different face-sheet materials were subjected to full-scale underwater blast testing. The panels were subjected to 1kg PE4 charge at a stand-off distance of 1 m. The panel with graded density core and carbon fiber face-sheets had the lowest deflection. Post-blast damage assessment was carried out using X-ray CT scanning. The damage assessment revealed that there is a trade-off between reduced panel deflection and panel damage. This research has been performed as part of a program sponsored by the Office of Naval Research (ONR)

A comparative analysis of pulp-derived nanocelluloses for 3D bioprinting facial cartilages

Nanocelluloses have attracted significant interest in the field of bioprinting, with previous research outlining the value of nanocellulose fibrils and bacterial nanocelluloses for 3D bioprinting tissues such as cartilage. We have recently characterised three distinct structural formulations of pulp-derived nanocelluloses: fibrillar (NFC), crystalline (NCC) and blend (NCB), exhibiting variation in pore geometry and mechanical properties. In light of the characterisation of these three distinct entities, this study investigated whether these structural differences translated to differences in printability, chondrogenicity or biocompatibility for 3D bioprinting anatomical structures with human nasoseptal chondrocytes. Composite nanocellulose-alginate bioinks (75:25 v/v) of NFC, NCC and NCB were produced and tested for print resolution and fidelity. NFC offered superior print resolution whereas NCB demonstrated the best post-printing shape fidelity. Biologically, chondrogenicity was assessed using real time quantitative PCR, dimethylmethylene blue assays and histology. All biomaterials showed an increase in chondrogenic gene expression and extracellular matrix production over 21 days, but this was superior in the NCC bioink. Biocompatibility assessments revealed an increase in cell number and metabolism over 21 days in the NCC and NCB formulations. Nanocellulose augments printability and chondrogenicity of bioinks, of which the NCC and NCB formulations offer the best biological promise for bioprinting cartilage

Low-cycle full-field residual strains in cortical bone and their influence on tissue fracture evaluated via in situ stepwise and continuous X-ray computed tomography

As a composite material, the mechanical properties of bone are highly dependent on its hierarchical organisation, thus, macroscopic mechanical properties are dictated by local phenomena, such as microdamage resulting from repetitive cyclic loading of daily activities. Such microdamage is associated with plastic deformation and appears as a gradual accumulation of residual strains. The aim of this study is to investigate local residual strains in cortical bone tissue following compressive cyclic loading, using in situ X-ray computed tomography (XCT) and digital volume correlation (DVC) to provide a deeper insight on the three-dimensional (3D) relationship between residual strain accumulation, cortical bone microstructure and failure patterns. Through a progressive in situ XCT loading–unloading scheme, localisation of local residual strains was observed in highly compressed regions. In addition, a multi-scale in situ XCT cyclic test highlighted the differences on residual strain distribution at the microscale and tissue level, where high strains were observed in regions with the thinnest vascular canals and predicted the failure location following overloading. Finally, through a continuous in situ XCT compression test of cycled specimens, the full-field strain evolution and failure pattern indicated the reduced ability of bone to plastically deform after damage accumulation due to high number of cyclic loads. Altogether, the novel experimental methods employed in this study, combining high-resolution in situ XCT mechanics and DVC, showed a great potential to investigate 3D full-field residual strain development under repetitive loading and its complex interaction with bone microstructure, microdamage and fracture

Preliminary Investigation of Beagle Dog as Substitute for Humans in Bioequivalence Studies

Purpose: To assess the suitability of beagle dog as an animal model for the evaluation of formulations in bioavailability and bioequivalence studies.Methods: A generic cetirizine 10 mg tablet formulation was compared with another reference formulation using beagle dog as animal model. A crossover oral comparative bioavailability study was conducted on cetirizine tablet 10 mg in healthy, male dogs under fasting conditions. The  formulations were administered orally with the aid of water. Serial blood samples were collected from pre-dose to 48.0 h post-dose and plasma concentrations of cetirizine were determined using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytical method. Pharmacokinetic parameters were calculated using  non-compartmental analysis while bioavailability was assessed using an analysis of variance (ANOVA) model for humans and dogs.Results: Cetirizine plasma concentrations in dog were comparatively  higher, in relation to human plasma concentrations, due to the smaller blood volume in former. There was a delay in time to reach maximum plasma concentration (Tmax) in dog. Cetirizine formulations were found to be bioequivalent in either of the species (dog and human). The ratio (test\reference) of least-squares mean for area under plasma concentration curve from time zero to last detectable concentration (AUC0-t), area under plasma concentration curve extrapolated to infinity (AUC0-‡ ) and maximum plasma concentration (Cmax), calculated for the dogs were comparable to those for humans. AUC0-t, AUC0-‡ and Cmax ratios ranged within 92.81 - 106.80 % for dogs and 95.43 . 104.84 % for humansConclusion: The results suggest that beagle dogs can be used in place of humans in bioequivalence tests on generic products of cetirizine.Keywords: Cetirizine, Beagle dog, Bioavailability, Bioequivalence, Pharmacokinetics, Noncompartmenta

Failure analysis using X-ray computed tomography of composite sandwich panels subjected to full-scale blast loading

The tailorable mechanical properties and high strength-to-weight ratios of composite sandwich panels make them of interest to the commercial marine and naval sector, however, further investigation into their blast resilience is required. The experiments performed in this study aimed to identify whether alterations to the composite skins or core of a sandwich panel can yield improved blast resilience both in air and underwater. Underwater blast loads using 1.28 kg TNT equivalent charge at a stand-off distance of 1 m were performed on four different composite sandwich panels. Results revealed that implementing a stepwise graded density foam core, with increasing density away from the blast, reduces the deflection of the panel and damage sustained. Furthermore, the skin material affects the extent of panel deflection and damage, the lower strain to failure of carbon-fibre reinforced polymer (CFRP) skins reduces deflection but increases skin debonding. A further two panels were subjected to a 100 kg TNT air blast loading at a 15 m stand-off to compare the effect of a graded density core and the results support the underwater blast results. Future modelling of these experiments will aid the design process and should aim to include material damage mechanisms to identify the most suitable skins

Composite nature of fresh skin revealed during compression

Biological systems are subjected to moderate-to-high strain rates in blast-type traumatic injuries. An improved understanding of the responses of cells and tissues to extreme mechanical stresses could improve mitigation and post-injury treatment strategies. A key aim of this research is to create biologically meaningful injury models of soft tissues. Here the authors examine the material and cellular properties of freshly harvested porcine skin in compression. The data presented suggest that fresh skin differentially responds low to moderate strain rates as a composite rather than that of a homogeneous polymer. The implications of this work are discussed in terms of creating improved analytical models to describe the material properties of fresh skin. The Centre for Blast Injury Studies acknowledges The Royal British Legion for its support, as well as Imperial College London. The Institute of Shock Physics acknowledges the support of the Atomic Weapon Establishment, Aldermaston, UK and Imperial College London.This is the accepted manuscript. The final version is available at http://www.icevirtuallibrary.com/content/article/10.1680/bbn.14.00028

Genotypic capacity of post-anthesis stem reserve mobilization in wheat for yield sustainability under drought and heat stress in the subtropical region

Wheat productivity is severely affected by drought and heat stress conditions worldwide. Currently, stem reserve mobilization (SRM) is receiving increased attention as a trait that can sustain wheat yields under adverse environments. However, the significance of SRM in sustaining wheat yields under drought and heat stress conditions remains uncertain in the tropical climate of Indo-Gangetic Plain region. Therefore, this study aimed to investigate genotypic variations in SRM in wheat and their influence on yield sustainability under drought and heat stress environments. The experiment was designed in an alpha-lattice layout, accommodating 43 genotypes under four simulated environments [timely sown and well irrigated (non-stress); timely sown and water-deficit/drought stress; late-sown and well-irrigated crop facing terminally high temperature; and late-sown and water-deficit stress (both water-deficit and heat stress)]. The water-deficit stress significantly increased SRM (16%–68%, p < 0.01) compared to the non-stress environment, while the heat stress conditions reduced SRM (12%–18%). Both SRM and stem reserve mobilization efficiency exhibited positive correlations with grain weight (grain weight spike−1) under all three different stress treatments (p < 0.05). Strong positive correlations between stem weight (at 12 days after anthesis) and grain weight were observed across the environments (p < 0.001); however, a significant positive correlation between stem weight and SRM was observed only with stress treatments. Results revealed that the SRM trait could effectively alleviate the impacts of water-deficit stress on yields. However, the SRM-mediated yield protection was uncertain under heat stress and combined water-deficit and heat stress treatments, possibly due to sink inefficiencies caused by high temperature during the reproductive period. Defoliated plants exhibited higher SRM than non-defoliated plants, with the highest increment observed in the non-stress treatment compared to all the stress treatments. Results revealed that wider genetic variability exists for the SRM trait, which could be used to improve wheat yield under drought stress conditions