Numerical analysis of low-velocity impact of carbon-basalt/epoxy hybrid laminates

349-355In this paper, an attempt has been made to numerically investigate the transient dynamic response of carbon-basalt/epoxy laminated composites subjected to low velocity impact. Carbon laminates are expensive hence, inclusion of cheaper basalt to obtain an improved, yet economical laminate is necessary. Finite element analysis (FEA) technique has been employed to simulate the laminated models. Loading profiles and test conditions from drop-weight tests have been obtained from literatures and necessary validation of FEA has also been performed. A correlation between impactor mass and velocity on the maximum laminate centre deflection has been established. In addition, the influence of hybrid stacking sequence and carbon position in the hybrid on laminate damage response has been studied. It has been observed from the study that hybrid 3 (H3) with stacking sequence CCBC-2 (best combination) showed the least deflection of all the stacking sequence sets and has the lowest deflection in all the low velocity impact testing conditions

Off-Axis and On-Axis Performance of Novel Acrylic Thermoplastic (Elium®) 3D Fibre-Reinforced Composites under Flexure Load

The flexure response of novel thermoplastic (Elium®) 3D fibre-reinforced composites (FRC) was evaluated and compared with a conventional thermoset (Epolam®)-based 3D-FRC. Ten different types of sample 3D-FRC were prepared by varying fibre orientations, i.e., 0°, 30°, 45°, 60° and 90°, and resin system, i.e., thermoplastic and thermoset. The bending characteristics and failure mechanisms were determined by conducting a three-point bend test. Results elucidate that The flexure response of novel thermoplastic (Elium®) 3D fibre-reinforced composites (FRC) was evaluated and compared with a conventional thermoset (Epolam®)-based 3D-FRC. Ten different types of sample 3D-FRC were prepared by varying fibre orientations, i.e., 0°, 30°, 45°, 60° and 90°, and resin system, i.e., thermoplastic and thermoset. The bending characteristics and failure mechanisms were determined by conducting a three-point bend test. Results elucidate that the on-axis specimens show linear response and brittle failure; in contrast, the off-axis specimens depicted highly The flexure response of novel thermoplastic (Elium®) 3D fibre-reinforced composites (FRC) was evaluated and compared with a conventional thermoset (Epolam®)-based 3D-FRC. Ten different types of sample 3D-FRC were prepared by varying fibre orientations, i.e., 0°, 30°, 45°, 60° and 90°, and resin system, i.e., thermoplastic and thermoset. The bending characteristics and failure mechanisms were determined by conducting a three-point bend test. Results elucidate that the on-axis specimens show linear response and brittle failure; in contrast, the off-axis specimens depicted highly nonlinear response and ductile failure. The thermoplastic on-axis specimen exhibited almost similar flexure strength; in comparison, the off-axis specimens show ~17% lower flexure strength compared to thermoset 3D-FRC. Thermoplastic 3D-FRC shows ~40% higher energy absorption, ~23% lower flexure modulus and ~27% higher flexure strains as compared to its thermoset counterpart

Multiscale damage modelling of 3D woven composites under static and impact loads

A multiscale progressive damage modelling methodology for 3-dimensional (3D) woven composites is presented. The proposed methodology is generic and can be implemented in most finite element software to create a digital twin for simulation of damage response. It uses 3D solid element (reduced integration) representation of the part for global analysis, while the local damage response, as well as matrix nonlinearity is modelled using a mesoscale constitutive unit-cell model of 3D woven composite consisting of idealised regions of polymer matrix and impregnated yarns. The idealised unit-cell model is defined based on realistic input from X-ray tomography of the 3D woven composite part and the micro-level constituent properties of the matrix and fibres. The damage model has been validated using quasi-static tensile/compression tests as well as dynamic drop-weight impact tests for both thermoset (epoxy) and thermoplastic (Elium) 3D woven composites. These simulations successfully demonstrate the accuracy and efficiency of the model for both 3D-textile composites.The authors would like to acknowledge the financial support provided by Universiti Teknologi PETRONAS (grant number 015LC0-197). The authors would also like to acknowledge the support of Dr. Pierre Gerard from Arkema and Dr. Sharp Keith from TexTech industries in acquiring Elium® resin and 3D fabric for this research work, Dr. Faiz Ahmad and Advance Functional Material (AFM) lab Universiti Teknologi PETRONAS in providing the facility for the fabrication of 3D woven composites

Structurally Homologous All β-Barrel Proteins Adopt Different Mechanisms of Folding

AbstractAcidic fibroblast growth factors from human (hFGF-1) and newt (nFGF-1) (Notopthalamus viridescens) are 16-kDa, all β-sheet proteins with nearly identical three-dimensional structures. Guanidine hydrochloride (GdnHCl)-induced unfolding of hFGF-1 and nFGF-1 monitored by fluorescence and far-UV circular dichroism (CD) shows that the FGF-1 isoforms differ significantly in their thermodynamic stabilities. GdnHCl-induced unfolding of nFGF-1 follows a two-state (Native state to Denatured state(s)) mechanism without detectable intermediate(s). By contrast, unfolding of hFGF-1 monitored by fluorescence, far-UV circular dichroism, size-exclusion chromatography, and NMR spectroscopy shows that the unfolding process is noncooperative and proceeds with the accumulation of stable intermediate(s) at 0.96M GdnHCl. The intermediate (in hFGF-1) populated maximally at 0.96M GdnHCl has molten globule-like properties and shows strong binding affinity to the hydrophobic dye, 1-Anilino-8-naphthalene sulfonate (ANS). Refolding kinetics of hFGF-1 and nFGF-1 monitored by stopped-flow fluorescence reveal that hFGF-1 and nFGF-1 adopts different folding mechanisms. The observed differences in the folding/unfolding mechanisms of nFGF-1 and hFGF-1 are proposed to be either due to differential stabilizing effects of the charged denaturant (Gdn+ Cl−) on the intermediate state(s) and/or due to differences in the structural interactions stabilizing the native conformation(s) of the FGF-1 isoforms

Compression and buckling after impact response of resin-infused thermoplastic and thermoset 3D woven composites

Damage tolerance of a unique resin-infused thermoplastic (Elium) 3D fibre-reinforced composite (3D-FRC) is compared with the conventional resin-infused thermoset (Epoxy) 3D-FRC using compression after impact (CAI) tests and finite element simulations. Higher damage tolerance is demonstrated for the thermoplastic 3D-FRC as its CAI failure strength and CAI stiffness is nearly insensitive to the impact energy levels and subsequent damage, while in contrast, both these properties for the thermoset 3D-FRC get compromised significantly. The buckling performance shows a gradual, almost linear, reduction in critical buckling (44.5% reduction in 0–100 J) for the thermoplastic 3D-FRC. In comparison, the thermoset 3D-FRC shows a much steeper drop in critical buckling, which becomes more pronounced for the higher impact energy cases (84.5% reduction in 0–100 J). It is postulated that the local plastic deformation of the thermoplastic matrix at the impact site as well as better interfacial adhesion is responsible for its better damage tolerance.The authors would like to acknowledge the financial support provided by Universiti Teknologi PETRONAS (grant number 015LC0-197). The authors would also like to acknowledge the support of Dr. Robert J. Barsotti from Arkema in acquiring Elium® resin, Dr. Faiz Ahmad and the Center of Advanced Functional Materials (AFM) in providing the facility for the fabrication of 3D composites

Synthesis of Novel Double-Layer Nanostructures of SiC–WOxby a Two Step Thermal Evaporation Process

A novel double-layer nanostructure of silicon carbide and tungsten oxide is synthesized by a two-step thermal evaporation process using NiO as the catalyst. First, SiC nanowires are grown on Si substrate and then high density W18O49nanorods are grown on these SiC nanowires to form a double-layer nanostructure. XRD and TEM analysis revealed that the synthesized nanostructures are well crystalline. The growth of W18O49nanorods on SiC nanowires is explained on the basis of vapor–solid (VS) mechanism. The reasonably better turn-on field (5.4 V/μm) measured from the field emission measurements suggest that the synthesized nanostructures could be used as potential field emitters

The role of MTOR pathway and growth factors as revealed by gene expression profiling in diffuse congenital hyperinsulinism

Congenital hyperinsulinism (CHI) is the commonest cause of recurrent and persistent hypoglycaemia in infants. Histologically there are two distinct types: focal and diffuse. The medical therapy for diffuse CHI involves diazoxide, glucagon and octreotide. The patients who are unresponsive to medical therapy require a near total pancreatectomy. However, this often fails to provide the best outcome as some patients continue to have recurrent hypoglycaemia whilst others develop diabetes mellitus in the long term. This study aimed to understand the gene expression pattern in the pancreatic tissues of the patients with diffuse CHI so as to identify novel mechanism(s) and therapeutic options. Gene expression microarray using RNA extracted from fresh frozen pancreatic tissue samples (obtained from children who underwent pancreatectomy) revealed significant overexpression of mammalian target of rapamycin (mTOR) and insulin-like growth factors in the diffuse CHI patients in comparison with normal controls. Immunostaining suggested an activation of mTOR pathway (which regulates cellular proliferation) in diffuse CHI and transdifferentiation of exocrine pancreatic elements into insulin producing cells, contributing to β-cell hyperplasia. Further clinical study on the role of the mTOR inhibitor sirolimus in patients with medically unresponsive diffuse CHI (who would have required pancreatectomy otherwise) revealed a good glycaemic response to sirolimus and the infants were able to come off intravenous fluids, glucagon and octreotide infusions, thereby preventing the need for a major surgery. Subsequent follow up to 12 months revealed that the patients were normoglycaemic on sirolimus therapy without any major side effects. Hence treatment with mTOR inhibitors offers an alternative therapeutic option for the patients with severe forms of diffuse CHI. Further studies involving larger group of patients to assess the long term safety and efficacy of mTOR inhibitors in the management of diffuse CHI are needed

Frictional complete contacts between elastically similar bodies subject to normal and shear load

AbstractThe problem of trapezium shaped punches pressed into a frictional, elastically similar half-plane and subject to sequential normal and shear loading is studied. The initial mix of stick, slip and separation regions is described, together with the steady state response when the shearing force is cycled. Conditions for full stick are established