Fragile Cover Research Articles

Failure analysis of a frangible cover made of short‐cut basalt fiber reinforced epoxy composites

AbstractThe frangible cover made of continuous fiber reinforced composites has become widely used structure for the new generation launch canisters. However, destroying the continuity of fibers is needed during the hand lay‐up process to make the frangible cover fail in predetermined patterns. In this article, composite frangible covers were fabricated with short‐cut basalt fiber reinforced epoxy(BF/Epoxy) composites instead of continuous fiber‐reinforced composite materials, reducing the strength redundancy in the local structure of the frangible covers. Tensile tests were firstly conducted on material samples to obtain the stress–strain characteristics of the short‐cut BF/Epoxy composites. The constitutive model and failure criterion of the short‐cut BF/Epoxy composites material were established. Then failure pressure and failure mode of the frangible covers were predicted by finite element method. Two frangible covers with different geometric parameter were fabricated and subjected to static bursting strength tests. The influence of structure parameter on the bursting pressure of the frangible cover was investigated in detail. it was found that the bursting pressure of the BF/Epoxy composite fragile cover can be tailored by adjusting the geometry size of the weak zones on surface of the cover. Meanwhile, Failure modes and the bursting pressure of the BF/Epoxy composite fragile covers are highly consistent with the predictions.Highlights A frangible cover made of the short‐cut basalt fiber reinforced epoxy(BF/Epoxy) composites was fabricated. The constitutive model and failure criterion were established based on the mechanical properties of the short‐cut BF/Epoxy composites. The static burst strength of the short‐cut BF/Epoxy composite frangible cover subjected to uniform pressure was investigated via both theoretical and experimental approaches. The short‐cut BF/Epoxy composite frangible cover eventually failed in accordance with the predetermined pattern. The simulation error of the failure pressure of the short‐cut BF/Epoxy composite frangible cover was less than 20%.

Simulation and Experimental Study of Mooring Function Composite Fragile Cover

Abstract Under the requirement that the fragile cover does not eject debris during missile launches, and to meet the demands of rapid combat, there is an urgent need for a lightweight missile launching system. Enhancing the effective utilization area of the fragile cover is an effective way to realize the lightweight of the missile launching system. This paper utilizes the properties of carbon fiber composite materials to design a novel frangible cover with mooring functionality and establishes numerical models for the cover’s pressure and bursting dynamics. In the pressure finite element model, the Tasi-Wu failure criterion is employed for damage assessment. In the bursting dynamics finite element model, a cohesive element is used to simulate the elastic behavior and damage evolution of the weak area, while a membrane element is employed to simulate the mooring function. Comparative analysis of numerical results with experimental data reveals minor discrepancies, with errors of 5.44% for maximum deformation under pressure and 8.1% for bursting force, respectively, validating the model’s rationality and effectiveness. Results from both experimental tests and finite element analyses demonstrate the successful implementation of mooring functionality in the segmented body. The effective utilization area of the cover was increased by 71.13%. This research provides a feasible direction for subsequent studies on non-ejecting frangible covers.

35.3: Study on Technology to Enhance the Strength of Display Module for Vehicle

This paper studies a scheme to enhance the strength of display module, which can solve the problem of fragile cover plate of vehicle display and other display module products. The principle of strength reduction of glass after processing is analyzed from the perspectives of internal stress, microcrack and molecular bond. The technical scheme of using CeO2 aqueous adhesive solution to remove the longitudinal microcracks of glass reduce the deep expansion of crack source in the stress layer, so as to increase the strength is described. Based on the experimental results, the overall strength of the product can be increased by 23–34%.

Subsoil carbon input by cover crops depends on management history

Cover crops represents an agricultural management option, which has the potential to increase soil carbon (C) stocks and contribute to atmospheric CO2 reduction. However, there is a scarcity of studies quantifying the C inputs from cover crops, particularly into subsoil layers. Furthermore, estimates of plant C inputs to soils often lack accounting of root fragments (here defined as roots in the size class of 0.25–4 mm) and net phyllo- and rhizodeposition. Based on a field experiment with multiple 13C-CO2 pulse labeling, we investigated the short-term C inputs from cover crop mixtures to 1-m depth in two long-term cropping systems with organic and conventional management. We used a novel 13C-based approach to quantify the amount of C in root fragments, as young fragile cover crop roots are challenging to sample in soils. The results showed that the total belowground C input to 1-m depth (570–1000 kg C ha−1) was similar across long-term management (organic and conventional, with or without a history of cover crops), but with a higher belowground C input for mixtures established without winter vetch (Vicia villosa Roth). The C input to the subsoil (> 25 cm) by cover crops accounted for 11–42% of the total plant belowground C input, which was significantly and negatively correlated to the soil fertility measured as the initial mineral nitrogen (N) content in the topsoil. The results suggest that root exploitation, and thus plant C inputs into the subsoil, was enhanced in relatively N poor cropping systems. Root fragments and net phyllo- and rhizodeposition accounted for 39–59% and 5–37%, respectively, of the total cover crop belowground C input, i.e., both representing significant pools of plant C input. We conclude that future studies on the effects of cover crops on soil C storage need to account for subsoil C pools including root fragments and rhizodeposition to achieve a comprehensive estimation of plant C inputs.

Structural Design and Impact Simulation of Glass Fiber Fragile Cover of Rocket

The fragile cover of rocket not only has the characteristics of sealing and high-temperature resistance, but also can break according to preset scratches when hited by the rocket’s head. In this paper, a penetrating glass fiber fragile cover with scratches is designed, and six structural types are set up with the number of layers laid by glass fiber as independent variables. Based on Hashin failure criterion and damage evolution law, the finite element method is used to simulate the process of rocket breaking through fragile cover and gas flow impinging fragile cover. The results show that the fragile cover will break along the preset scratches, which does not produce debris to interfere with rocket launch. As the number of glass fiber cloth layers increases, the Mises stress of the rocket’s head increased when the fragile cover broken. The impact of the gas flow on the fragile cover of the adjacent pipe is not uniformly distributed, and the maximum value of the Mises stress appears at the scratches of the cover body. As the number of glass layers decreases, the failure index value of the fragile cover under the impact of gas flow increases. The research provides a reference for the design of rocket glass fiber fragile cover.

Drift sands, lakes, and soils: the multiphase Holocene history of the Laarder Wasmeren area near Hilversum, the Netherlands

AbstractA unique complex of multiphased Holocene drift sands and paleosols, with at least two lacustrine phases, was discovered during a major sanitation project in the Laarder Wasmeren area near Hilversum, the Netherlands. The complex could be studied in detail, highly facilitated by the excellent and large-scale exposure of the various deposits and soils. OSL dating was used to establish ages of the phases, where possible differentiating between time of deposition and time of burial by taking into account the potential effects of bioturbation. Pollen analysis served to reconstruct the vegetation during the various phases.A first minor phase of aeolian activity already started before approx. 5,000 BC, followed around 4,000 BC by a second phase and a rather massive third phase around 3,000 BC. After a long phase of soil formation, the latest, massive drift sand phase started around the 14th to 15th century. It clearly represents the classic drift sand phase that started in the Late Middle Ages in the Netherlands. Sand drifting followed on soil forming phases during which the vegetation became increasingly dominated by ericaceous plants and culminated in heathlands. The first three aeolian phases and associated heathlands are much older than generally assumed for heathland and drift sand to occur in the Netherlands. Moreover, podzolisation was found to have started very early, true podzols already occurring before 4,000 BC.Around 3,000 BC groundwater in the area reached a maximum altitude of about 230 cm +NAP, resulting in local open water in the area. This rise is probably linked to the development of the Dutch coastal area, where at that time peat accumulated and drainage was poor, inducing a rise of the groundwater level in ‘het Gooi’. This groundwater level fell later on, to never reach this altitude again. The Groot Wasmeer was formed by local stagnation on a slowly permeable podzol and already reached a level of 320-325 cm +NAP by 400 BC, which more or less equals its 20thcentury level.The results demonstrate that earlier concepts on the occurrence and age of aeolian phases, podzols and heathland vegetations in the Netherlands are far too schematic, and that early, pre-agricultural cultures may already have had an impact on the stability of fragile cover sand landscapes, e.g. through burning. Results are in line with those from several contemporary studies on early prehistoric cultures and their impact in river dune areas in the Central and Eastern Netherlands.

The use of tissue culture chamber slides in the fluorescent staining of virus infected cells

Z n The specificity of the fluorescein-labeled antibody staining technique in identifying and localizing viral antigens in cells was first demonstrated by Coons and co-workers in 1950 {1). Since then it has been used extensively. In most laboratories, cells are grown and infected on cover slips and handled either individually or in batches in specially designed racks. In order to avoid some of the problems of handling fragile cover slips, various chambers have been designed to attach to regulation glass microscope slides {2-6}. These chambers allow the local staining of areas of cells with small amounts of sera, and the use of treated and control areas on the same cell sheet combined with the convenience of handling of regular microscope slides: for therinsing and washing stages.