116 research outputs found
Novel Design of Cocured Composite ‘T’ Joints with Integrally Woven 3D Inserts
No full textComposites can be exploited to their full potential when cocured, wherein different parts are made and bonded together in a single cure operation to realise an integral structure. The key element in a typical cocured construction is T-joint, which forms the primary load transfer mechanism between the skin and stiffener in a structural assembly. T-joints are particularly vulnerable for pull off loads and researchers are looking at various techniques to improve the pull strength viz. stitching, tufting, 3D weaving, multilayer weaving, 3D braiding and the like. The present work uses a novel technique to improve the strength of T-joints by employing a hybrid design wherein an integral 3D ‘T’ insert is interleaved with a conventional T-joint. Inserts were woven using 3K and 6K carbon tows and incorporated in T-joints using CSIR-NAL proprietary process called ‘Vacuum Enhanced Resin Infusion Technology (VERITy)’ process. Several configurations of T-joints were tested in an UTM in the pull mode till the failure to assess the efficacy of integrally woven 3D inserts. It was observed that the initial failure load was nearly the same across the various T-joint configurations tested whereas the maximum failure loads were quite different. The normalised strength of T-joints with integrally woven 3D inserts in pull off mode was enhanced by about 30% when compared T-joints without the insert and thus vindicating the usage of integrally woven 3D insert in a cocured T-joint. The insert is conceived in such a way that it can be easily incorporated in the design of cocured structures
Hazard potential of apparel textiles
No full text157-160<span style="font-size:11.0pt;line-height:115%;
font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:minor-latin;="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The
hazard potential of 25 commonly used fabrics has been characterized in terms of
flame temperature during and rate of burning. It is observed that the weight of
the, fabric has profound influence .on both, rate of burning and flame
temperature during burning.</span
Enhanced crystallographic and physicochemical properties of chromium-embedded ZnO nanoparticles
No full textZinc oxide (ZnO) nanoparticles (NPs) have been of growing interest due to their scientific and technological importance. The physicochemical properties of these NPs can be tailored by doping with different transition metals. In this study, Pure ZnO and Chromium (Cr) doped ZnO [Zn0.5-xCrxO (x = 0.02, 0.04, and 0.06 M)] NPs have been prepared by the chemical combustion method. The influence of Cr doping on the physicochemical properties of ZnO NPs was examined using XRD, FTIR, Raman, SEM, UV–visible absorption, and ZP/PSA data. The average crystallite size of as-synthesized pure ZnO (PZ), calcinated ZnO (CZ), Zn0.48Cr0.02O (ZC2), Zn0.46Cr0.04O (ZC4) and Zn0.44Cr0.06O (ZC6) samples are found to be 55, 59, 43, 39, and 34 nm respectively, evident by XRD. Increasing Cr doping reduces average crystallite size in ZnO due to lattice distortion by Cr3+ ions. FTIR spectroscopy confirms Cr presence in Zn0.5-xCrxO NPs, verifying ZnO formation. The size confinement effect on the optical bandgap (Eg) due to the effect of Cr doping is corroborated by UV-visible absorption studies. The Tauc method determined an increased Eg in Zn0.5-xCrxO NPs with higher Cr doping concentrations, attributed to reduced particle size which is also evident by XRD and SEM. Zeta potential (ZP) values endorse that the synthesized ZnO and Zn0.5-xCrxO NPs have good colloidal stability. Zn0.5-xCrxO NPs exhibited enhanced physicochemical properties than the ZnO NPs which is a notable feature of nanomaterials
Damage Characteristics & Residual Compression Strength of CFRP Laminates manufactured using VERITy Subjected to Low Velocity Impact
No full textComposite materials are widely used in aerospace structures mainly due to their high specific strength and stiffness, coupled with increased durability and lower maintenance costs. Most primary composite aero structures use prepreg based autoclave moulded Carbon epoxy composites. Advanced Composites Division of CSIR-NAL has developed and patented a resin infusion technique called Vacuum Enhanced Resin Infusion Technology (VERITy) for the development of co-cured wing for the SARAS-PT3 aircraft using Carbon fabric and Epoxy resin. Carbon based laminated composites, are generally known to be vulnerable to impact damages such as tool drop. Damage due to low velocity impact on laminated composites can be dangerous since they can lead to significant reduction in strength even when it is barely visible to naked eye. Post-impact tests such as compression-after-impact or tension-after-impact have been used to study the degradation in strength and quantify the effect of impact damage.
This report presents the damage characteristics and residual compression strength of Carbon epoxy laminates processed using VERITy and subjected to low velocity impact under room temperature ambient (RTA) condition. Carbon UD Fabric G 0827 BB1040 HP03 1F manufactured by Ms. Hexcel Composites is used as the reinforcement. The resin system is Epolam 2063 supplied by M/s. Axson. Dent depth, damage area and post-impact residual compression strength are measured for laminates of various thicknesses and impact energies
Stress Analysis of Ailerons-control bracket attachment to front-spar in SARAS composite wing
No full textThis report presents the FE stress analysis of Aileron-control bracket attachment to front-spar in SARAS composite wing. The wing is having eight aileron control brackets attached to fiont-spar between sta#4 to sta#21. During the actuation of the aileron. the force is transferred to the bracket by metallic tubes which are connected trough bracket. These forces are reacted by the front-spar and front-spar gussets to which the brackets are attached through fasteners. Each bracket should be able to transfer the actuator load efficiently and it is necessary to ensure the strength and stiffness of the surrounding parts for the smooth operation of the aileron. Brackets and attachment are modeled in detail and the brackets are integrated with global wing model. FE stress analysis is carried out for all
three design ultimate load conditions. Failure-index of composite part is extracted on the basis of Yamada-Sun failure criteria. It is found that failure-index of front-spar which is connected with aileron-bracket to front-spar and front-spar gusset, the fastner forces are also extracted. Margin of safety for shear-strenth of fasteners and bearing-stress of CFC and metal connections are also positive
Role of Manthana Samskara in the preparation of Khajitha Pinda Taila
No full textThe term "Bhaishajya" denotes "drug" or "medicine," whereas "Kalpana" pertains to "preparation." Bhaishajya Kalpana encompasses the application of various medicinal substances and adheres to specific principles outlined in ancient Ayurvedic scriptures. This discipline is divided into two primary principles: Aushadha Nirmana (the Principle of Formulation) and Aushadha Prayoga (the Principle of Therapeutic Application). A thorough understanding of these core concepts is vital for effective research and development in Ayurvedic pharmaceutics. Sneha Kalpana is one among those preparations derived from the basic Kalpanas prepared using either Ghritha or Taila. The transformation of properties into the Sneha Dravya is made possible by the use of various Samskaras. Manthana Samskara is believed to help in the proper mixing of two substances and also imbibe Sheeta Guna to the formulation. It is considered to give a homogenous mixture thereby improving the product’s stability to a greater extent. Pinda Taila is one such Yoga mentioned in our classics for the relief of Daha and Shoola developed in Vatarakta after subjecting it to Khajita Samskara/Manthana Samskara
Thermal residual stress investigation in Al 2024/ Cu-Al-Ni adaptive composites by X-Ray diffractometer
No full textStress Analysis of Composite wing of SARAS Aircraft at extreme operating temperatures
No full textThis report presents the FE stress analysis of SARAS Composite wing due to thermal load and structural loads (flight and landing loads). This structure is expected to operate at extreme temperature (-54OC and 71°C). The stress analysis of composite wing with these thermal loads along with structural loads assumes more importance in view of the
directional dependence of co-efficient of thermal expansion between various members. The joints between metallic landing beams and surrounding composite structure are
investigated. These joints are subjected to shear transfer at the fastener locations due to difference in co-efficient of thermal expansion between composite and metallic materials. FE analysis of wing is carried out with combination of thermal and critical flight and landing load cases. FE analysis shows that the structure is safe from strength point of view. Failure-indies are less than 1.0. Also, the fasteners forces and corresponding bearing stresses are calculated at the landing gear beam joint to composite structure. The margin of safety for fasteners shear and bearing are positive showing that the joints are
safe
Experimental and finite element numerical studies on the post-buckling behavior of composite stiffened panels
No full textAircraft composites structures are typically made using stiffened skin construction as it provides a minimum weight solution to many design problems. However, designers are reluctant to allow composite stiffened structures to operate in the post-buckled load regimes due to their poor inter-laminar properties. The post-buckling response of cocured composite stiffened panels is explored by experiments and numerical simulations. An integrated progressive damage finite element model is presented which captures inter and intra-laminar failures in panels. Detailed analysis of measured experimental structural responses in terms of strain, deformations, the failure mode is carried out and validated from the numerical analysis
Design of End Casting for Thin Composite Stiffened Panels Subjected to Axial Compression Load
No full textCompression testing of large, thin, stiffened composite panels is complex due to the susceptibility of such panels to premature buckling and failure. Such failures are due to the artifacts of testing, such as, offset at load introduction edges, non-uniform distribution of loads, nature of lateral supports, crushing of panel edges etc. In this paper, a novel approach for compression loading of thin stiffened composite panels is proposed and validated from finite element analysis supported by tests. Compression loading of such panels (less than 2mm thick) is
challenging since the edges are susceptible to local crushing. To avoid this, loading edges of the panel were encased in mild steel casing blocks filled with finely grounded aluminium powder mixed with epoxy resin. Coupon level tests were conducted to measure mechanical properties of the interface between composite and casting mixture. Digital Image Correlation (DIC) technique was used in these tests to measure the full field strains and to validate
numerical simulations. Further, finite element analysis of the actual composite test panel with end casting mixture was performed which indicated that interface shear stresses and compression stresses at maximum expected load are much lower than allowables obtained from specimen tests. Hence, the Aluminium-Epoxy cast mixture proposed in this study can be used safely to cast edges of large stiffened panels for axial compression tests
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