Development of Cytoplasmic–Nuclear Male Sterility, Its Inheritance, and Potential Use in Hybrid Pigeonpea Breeding

Pigeonpea [Cajanus cajan (L.) Millsp.] is a unique food legume because of its partial (20–30%) outcrossing nature, which provides an opportunity to breed commercial hybrids. To achieve this, it is essential to have a stable male-sterility system. This paper reports the selection of a cytoplasmic–nuclear male-sterility (CMS) system derived from an interspecific cross between a wild relative of pigeonpea (Cajanus sericeus Benth. ex. Bak.) and a cultivar. This male-sterility source was used to breed agronomically superior CMS lines in early (ICPA 2068), medium (ICPA 2032), and late (ICPA 2030) maturity durations. Twentythree fertility restorers and 30 male-sterility maintainers were selected to develop genetically diverse hybrid combinations. Histological studies revealed that vacuolation of growing tetrads and persistence of tetrad wall were primary causes of the manifestation of male sterility. Genetic studies showed that 2 dominant genes, of which one had inhibitory gene action, controlled fertility restoration in the hybrids. The experimental hybrids such as TK 030003 and TK 030009 in early, ICPH 2307 and TK 030625 in medium, and TK 030861 and TK 030851 in late maturity groups exhibited 30–88% standard heterosis in multilocation trials

The key role of thread and needle selection towards ‘through-thickness reinforcement’ in tufted carbon fiber-epoxy laminates

Tufting of dry preforms is one of the means of accomplishing through-thickness reinforcement (TTR) in a liquid composite molding process. Herein, once a preform is laid up, an automated robotic tufting setup is used to introduce the TTR. The selection of thread and needle for tufting process go hand-in-hand as tufting operation involves the act of penetrating preform by the needle as well as the trauma thread has to endure during this act. This paper explores the methodology of thread and needle selection through studies at different levels right from tufting of preforms to testing of tufted laminates. Glass, carbon and Kevlar threads in combination with a tufting needle and two different sewing needles are explored in this study. The effect of tufting speed on the quality of tuft is analyzed in terms of damage of fabric yarn, thread, and needle breakage. Layer-wise analysis of damage due to needle penetration in fabric yarns is carried out. Key mechanical properties of tufted composite samples are evaluated to determine the effect of tufting on the in-plane and out-of-plane properties

Damage Tolerance of Stiffened Skin Composite Panels

This work discusses design, fabrication and damage tolerance evaluation of co-cured skin stringer carbon fiber composite panels. Such stiffened panels are typically found in aircraft wing skins. Composite panels representing a portion of an aircraft wing box are designed and fabricated using Carbon fiber and epoxy matrix using resin infusion process. Fixtures to support the panels during low velocity impact tests are also designed and fabricated. A drop tower is used to conduct impact tests. Panels are subjected to various impacts to study the effect of impact energy on damage visibility and damage size. Impacts are also categorized according to their location: (a) Impact exactly above stringer, (b) Impact above skin, and (c) Impact above stringer flange. The extent of damages is studied based on non-destructive inspection techniques such as ultrasonic inspection. Further, one of the panels containing impact damages is subjected to residual strength test. Displacements and strains are measured using digital image correlation technique and resistance strain gages. Finite element model of the panel is also developed. Deformations and strains obtained from FE simulations are compared with test data. Results show that impact damages did not alter the load path significantly in the composite panel

Master process sheets for fabrication of CFC centre fuselage parts of TEJAS (Light Combat Aircraft): part-2

The centre fuselage has a complex geometry with doubly curved surfaces. This presents a greater challenge in the realization of airworthy composite components. The mouldability of composites is exploited to produce composite tools, which capture the complex geometry. The stiffened composite parts on these composite tools are made by co-curing technology involving the bonding of stiffeners to the skin in a single operation. These stiffeners on contoured components need to be aligned vertically with the required spacing. Most of these parts have non-developable surfaces, which are not amenable for lay-up with computer generated transfer foils. The lay-up is done using prepregs pf smaller width, which is similar to tow placement, to facilitate the lay-up. The heart of co-curing technology lies in the design and fabrication of tooling. The tools should have precise contour and dimensional stability. NAL has adopted a unique philosophy in the tooling technology based on the experience of cocuring such components. The lay-up tools of stiffeners are stiff so that they maintain the required contour and alignment. The curing tools are different from layup tools and are flexible enough to achieve the required compaction of the web of stiffener. This concept allows the uniform application of autoclave pressure on webs of stiffeners and skin. The stiffeners and joint configurations vary from part to part. Some of the parts have stiffeners running orthogonal to each other and both are continuous at their junctions. The co-curing technique has to be suitably modified to redesign the layup and curing tools. Some of the parts have a Y joint, which allows the integration of floor of fuel tank without a mechanical joint in that region avoiding fuel leakage through joints. This is achieved by an innovative design using assembly of external moulds during lay-up. One of the parts has stiffeners, which are curved in height and curved in length to follow spine contour. The tools are fabricated to suit the contour and the required stiffener spacing. The technology to produce these complex composite components is developed over a period of time. The tools required for the layup at critical areas like bermuda triangle, assembly of cores on skin and fixtures for curing etc. are developed to facilitate faster and controlled production. The fine tuned process for Production of LCA is documented in greater details with step-by-step operations augmented with figures to assist the production at shop floor