Chip formation in machining of unidirectional carbon fibre reinforced polymer laminates : FEM based assessment

Finite-element (FE) method offers a low cost virtual alternative to assist in optimisation of critical process parameters in machining of composites. This study is focussed on understanding the mechanics of chip formation in orthogonal cutting of unidirectional (UD) carbon-fibre-reinforced polymer (CFRP) laminates through development of FE models. Machining responses of UD CRFP laminates with fibre orientation of 45° (measured with respect to the cutting direction) are assessed. Modelling of material removal in the form of fragmented chips is considered. Damage initiation is determined using the Hashin stress criterion for the fibre component, while matrix failure predicted using Puck criteria. Subsequent damage evolution events are modelled using a strain-based softening approach to degrade relevant material properties linearly. Primary numerical results compared with experimental data revealed that developed FE models are able to predict global machining responses (i.e. cutting forces) and characterise various discrete damage modes associated with machining response of quasi-brittle CFRP laminates successfully. The models also provide a valuable insight into variation in chip morphology

Study of the machining induced damage in UD-CFRP laminates with various fibre orientations : FE assessment

Finite elements (FE) provide an excellent and low-cost approach in the assessment of composite machining induced damage. This article is focused on the evaluation of the damage underlying the machined surface through the development of a novel 3D FE model in composite machining. Sub-surface damage of UD-CFRP with fibre orientations from 0o to 90o is evaluated. An algorithm to assess composite damage evolution and chip formation is inserted via user-defined subroutine. Damage initiation is determined using Hashin’s failure criteria for fibre damage modes, while matrix damage modes are assessed via Puck’s failure criteria. Subsequent damage evolution is modelled using an energy-based linear damage degradation law. Numerical results reveal relevant advances in the prediction of the damage induced underlying the machined surface for fibre orientations from 60o to 90o obtained in previous investigations

Ferromagnetic ZnO Nanocrystals and Al-induced Defects

ZnO nanocrystals (NCs) capped with polyvinyl pyrrolidone reveal room temperature ferromagnetism. Incorporation of Al3+-ions induce defects in ZnO NCs leading to quenching of excitonic luminescence of ZnO at the cost of an increase in the intensity of oxygen vacancy related emission. Photoluminescence excitation spectra exhibit an additional hump like feature attributed to Al-doping. Saturation magnetization of Al3+-doped ZnO NCs is the same as that of the undoped ZnO NCs. However, a remarkable decrease in the coercivity associated with change in the nature of M (T) curve and electron paramagnetic resonance signal with g = 1.96 is observed consequent to Al doping. The results provide direct evidence of the defects within the core of NCs that are responsible for the ferromagnetic ordering in the Al3+-doped ZnO. The M(T) curve unravels a typical exchange mechanism

Evidence for complete and partial surface renewal at an air-water interface

A wind-wave flume is used to determine the extent to which the thermal boundary layer (TBL) at a wind-forced air-water interface is completely renewed from below. We measure skin temperature, Tskin, radiometrically, temperature immediately below the TBL, Tsubskin, using a temperature profiler, and net heat flux using the gradient flux technique. The Tskin probability density function, p(Tskin), and surface renewal time scale, τ, were measured using passive and active infrared imaging techniques, respectively. We find that the mean percentile rank of Tsubskin in p(Tskin) is 99.90, implying that complete surface renewal occurs. This result suggests an alternative to radiometric measurement of Tskin through the simple combination of an infrared camera and an in situ temperature sensor. Comparison of the temperature difference across the TBL to the expected cooling implies that a significant portion of events only partially renew the TBL. This result should impact efforts to improve air-sea transfer models

Ballistic damage in hybrid composite laminates

Ballistic damage of hybrid woven-fabric composites made of plain-weave E-glass-fabric/epoxy and 8H satin-weave T300 carbon-fabric/epoxy is studied using a combination of experimental tests, microstructural studies and finite-element (FE) analysis. Ballistic tests were conducted with a single-stage gas gun. Fibre damage and delamination were observed to be dominating failure modes. A ply-level FE model was developed, with a fabric-reinforced ply modelled as a homogeneous orthotropic material with capacity to sustain progressive stiffness degradation due to fibre/matrix cracking, fibre breaking and plastic deformation under shear loading. Simulated damage patterns on the front and back faces of fabric-reinforced composite plates provided an insight into their damage mechanisms under ballistic loading

Synthesis of photoactivable Pt(IV) prodrug loaded on NaYF4 based upconversion nanoparticles functionalized with 2-deoxy-D-glucose and its evaluation for targeted cancer therapy

21-30Nano-formulation based on Tm, Yb doped NaYF4 upconversion nanoparticles (UCNPs) functionalized with 2-deoxy-D-glucose have been synthesized to load the photoactivable Pt(IV) prodrug, cis-[PtI2(NH3)2(OCOCH2CH2COOH)2]. The Pt(IV) prodrug has been synthesized by oxidation of cis-[PtI2(NH3)2] to [PtI2(OH)2(NH3)2] and its further treatment with succinic anhydride. It is loaded through ester bond formation between the carboxyl groups of Pt(IV) prodrug with hydroxyl groups of 2-deoxy-D-glucose (2-DG) coated on UCNPs. The cytotoxicity of formulation after exposing to 385 nm UV light and in absence of light is evaluated against MCF-7 cell lines by MTT assay. The results have revealed enhanced cytotoxicity of UV exposed nano-formulation. Additionally, the clonogenic assay has exhibited the decrease in plating efficiency as inferred from decreased surviving fraction around 20% only for UV activated formulation as compared to formulation in dark, as well as merely Pt(IV) prodrug. These results are indicative that more internalization of the formulation inside the cancer cells was achieved due to the presence of 2-DG rendering more efficiency to kill cancer cells

A novel finite element method approach in the modelling of edge trimming of CFRP laminates

Nowadays, the development of robust finite element models is vital to research cost-effectively the optimal cutting parameters of a composite machining process. However, various factors, such as the high computational cost or the complicated nature of the interaction between the workpiece and the cutting tool significantly hinder the modelling of these types of processes. For these reasons, the numerical study of common machining operations, especially in composite machining, is still minimal. This paper presents a novel approach comprising a mixed multidirectional composite damage mode with composite edge trimming operation. An ingenious finite element framework which infer the cutting edge tool wear assessing the incremental change of the machining forces is developed. This information is essential to replace tool inserts before the tool wear could cause severe damage in the machined parts. Two unidirectional carbon fibre specimens with fibre orientations of 45∘ and 90∘ manufactured by pre-preg layup and cured in an autoclave were tested. Excellent machining force predictions were obtained with errors below 10% from the experimental trials. A consistent 2D FE composite damage model previously performed in composite machining was implemented to mimic the material failure during the machining process. The simulation of the spring back effect was shown to notably increase the accuracy of the numerical predictions in comparison to similar investigations. Global cutting forces simulated were analysed together with the cutting tool tooth forces to extract interesting conclusions regarding the forces received by the spindle axis and the cutting tool tooth, respectively. In general terms, vertical and normal forces steadily increase with tool wear, while tangential to the cutting tool, tooth and horizontal machining forces do not undergo a notable variation

One pot synthesis of luminescent Mn doped ZnSe nanoparticles and its silica based water dispersible formulation for targeted delivery of doxorubicin

The manganese doped zinc selenide nanoparticles (ZnSe:Mn NPs) were synthesized by thermolysis method using oleic acid and oleylamine as a capping agent, 1-octadecene as solvent. Coating of mesoporous silica was done on ZnSe:Mn (ZnSe:Mn@mSilica) which was further functionalized with amine functional groups by treating with (3-aminopropyl)trimethoxysilane. Further pegylation was done to achieve water dispersibility by conjugating carboxyl groups of poly(ethylene glycol) diacid with the amine groups. These pegylated NPs were subsequently treated with ethylenediamine followed by acrylic acid. Conjugation of tris-(hydroxymethyl-aminomethan) was performed by Michael-type addition reaction to afford ZnSe:Mn@mSilica-PEG-Tris-OH. These TRIS functionalized NPs exhibited broad emission ranging from 590-620 nm that is an indicative for their suitability in diagnosis and monitoring progress of cancer treatment. To explore the usefulness of increased surface area because of mesoporosity, doxorubicin was loaded on ZnSe:Mn@mSilica-PEG-Tris-OH NPs through silyl ether linkage and evaluated for cytotoxicity against WEHI-164 mouse fibrosarcoma and RAJI human hematopoietic origin cancer cell lines. A decrease in 12 % of cell viability of WEHI-164 cells while 30% decrease in RAJI cell lines (IC50 ≈ 45 nM) were observed.  This shows that our formulation has more cytotoxic in RAJI cancer cell lines than that of WEHI-164 cancer cells. These results revealed that the formulation has potential for the application in drug delivery and diagnosis in chemotherapeutics

One pot synthesis of luminescent Mn doped ZnSe nanoparticles and their silica based water dispersible formulation for targeted delivery of doxorubicin

348-355The manganese doped zinc selenide nanoparticles (ZnSe:Mn NPs) have been synthesized by thermolysis method using oleic acid and oleylamine as capping agents, and 1-octadecene as solvent. Coating of mesoporous silica is done on ZnSe:Mn (ZnSe:Mn@mSilica) which is further functionalized with amine functional groups by treating with (3-aminopropyl)trimethoxysilane. Further pegylation is done to achieve water dispersibility by conjugating carboxyl groups of poly(ethylene glycol) diacid with the amine groups. These pegylated NPs are subsequently treated with ethylenediamine followed by acrylic acid. Conjugation of tris-(hydroxymethyl-aminomethane) is performed by Michael-type addition reaction to afford ZnSe:Mn@mSilica-PEG-Tris-OH. These tris functionalized NPs have exhibited broad emission ranging from 590-620 nm that is an indicative for their suitability in diagnosis and monitoring progress of cancer treatment. To explore the usefulness of increased surface area because of mesoporosity, doxorubicin is loaded on ZnSe:Mn@mSilica-PEG-Tris-OH NPs through silyl ether linkage and evaluated for cytotoxicity against WEHI-164 mouse fibrosarcoma and RAJI human hematopoietic origin cancer cell lines. A decrease in 12% of cell viability of WEHI-164 cells while 30% decrease in RAJI cell lines (IC50 ≈ 45 nM) are observed. This shows that our formulation has more cytotoxic in RAJI cancer cell lines than that of WEHI-164 cancer cells. These results reveal that the formulation has potential for the application in drug delivery and diagnosis in chemotherapeutics

3D Finite Element Modelling of Cutting Forces in Drilling Fibre Metal Laminates and Experimental Hole Quality Analysis

Machining Glass fibre aluminium reinforced epoxy (GLARE) is cumbersome due to distinctively different mechanical and thermal properties of its constituents, which makes it challenging to achieve damage-free holes with the acceptable surface quality. The proposed work focuses on the study of the machinability of thin (~2.5 mm) GLARE laminate. Drilling trials were conducted to analyse the effect of feed rate and spindle speed on the cutting forces and hole quality. The resulting hole quality metrics (surface roughness, hole size, circularity error, burr formation and delamination) were assessed using surface profilometry and optical scanning techniques. A three dimensional (3D) finite-element (FE) model of drilling GLARE laminate was also developed using ABAQUS/Explicit to help understand the mechanism of drilling GLARE. The homogenised ply-level response of GLARE laminate was considered in the FE model to predict cutting forces in the drilling process