This study executed an objective comparison between Resin Infusion methods currently used, providing a level comparison in identical circumstances. Six different resin infusion methods including ...VARTM, SCRIMP, CAPRI, DBVI, VAP, and PI were investigated to discern if the modifications made relevant to the standard VARTM process have a distinguishable effect, and how significant the effect was. Process parameters were found to vary significantly between methodologies, with large differences in infusion time, laminate pressure and relaxation, and resin usage. Fibre volume fractions were found to vary significantly both between methodologies and along the infusion length of some panels. Differences of up to 13% and 10% were found in short beam strength and compression strength between the infusion methods. There was found to be no significant difference in void content between methodologies once the best process parameters had been established, with the exception of PI which resulted in a significant increase.
Autoclave prepreg processing is commonly used to produce high-quality structural components. Unlike in flat geometries, defects such as corner thickening, wrinkling and voids may be generated within ...complex structures during processing. This research investigates defect formation within the layup, debulking and consolidation stages of processing, focused on female moulded corners with high thickness to radius ratios. The influence of varying corner radii and proportion of 0°-fibres on the formation and size of corner defects was investigated. The wrinkling severity, corner thickening, and material flow behaviour of the samples was quantified through optical microscopy analysis. To characterise laminate corner-thickness variation following each processing step (layup, debulking, consolidation), a non-destructive laser measurement method was developed. It is demonstrated that corner thickening initially occurs during the layup and debulking process. Visualisation of the prepreg mass flow in corners shows that a higher 0°-fibres content increases the shear flow of the material during consolidation.
Understanding the effect a flexible structure has on the loads and responses during slamming events will improve the design process for high speed marine craft. Design of hulls is typically ...undertaken on the assumption that the pressures applied are the same as if the hull was rigid. In reality the loads may vary due to the hydroelasticity resulting from the fluid structure interaction during the impact. This work characterises the variations in both applied pressure and panel response due to the hydroelasticity. Impacts have been undertaken using a purpose built servo-hydraulic slam testing system with impact velocities up to 6.0m/s and a deadrise angle of 10°. The unsupported panel area was set at approx 1000×500mm with simply supported boundaries along all four edges. Clear trends between a panel׳s flexibility and the total force and applied pressure have been observed. The changes in both loads and responses are largest at the centre and chine edge of the panel and can be related to the regions of the most significant changes in local velocity (centre) and deadrise angle (chine). Changes in the loads and responses for sandwich constructions can be attributed to the shear stiffness and shear factor as well as the flexural rigidity.
•Impacts undertaken with velocities up to 6.0m/s and a deadrise angle of 10°•Trends between panel׳s flexibility, total force and applied pressure are observed.•Correlation shown between panel rigidity and a decreasing peak pressure at the centre.•Decreases in local velocity centre of up to 72.6% observed at 4.0m/s.•Decreases in deadrise angle at outer edge up to 11°, negative local deadrise angle.
Use of sandwich constructions in slamming regions of high speed marine craft has led to increased consideration of the applied transverse shear force. Low shear strength core materials can lead to ...transverse shear failure becoming a high risk failure mode. Direct measurement of transverse shear force is difficult without altering the structure of the hull panels. This work utilises a non-invasive strain derivative method to estimate the applied transverse shear force. The basis of this method is the correlation between applied bending moment, determined from surface mounted strain gauges, and transverse shear force. A simply supported 1000×500mm instrumented sandwich panel has been tested in the Servo-hydraulic Slam Testing System. Impacts have been undertaken at 10° with vertical velocities from 1.0 to 3.5m/s. The shear force to bending moment ratio has been compared with the ratio based on a uniformly distributed load, as frequently used in design. An increase of up to 68% for the slamming experiments is observed. This significant difference illustrates a greater applied transverse shear force in slamming regions than would be predicted through the application of a uniformly distributed load.
Slamming, the impact between a marine craft’s hull and the water surface is a critical load case for structural design of marine vessels. The importance of hull slamming has led to a significant body ...of work to understand, predict and model these impacts. There is however, a lack of experimental data for validation, particularly for deformable panels and sandwich structures. This paper describes a high-velocity panel slamming test system that enables the generation of comprehensive and reliable experimental data on slamming impacts for both rigid and flexible panel structures. The pressure magnitudes, time-histories and spatial distributions resulting from testing of a nominally rigid panel have been compared with previous analytical, semi-empirical and experimental studies. Slamming impacts of a deformable sandwich panel are shown to cause different pressures to those from a rigid panel impact, resulting in increased transverse shear loading at the panel edge.
ABSTRACT
The accuracy of theoretical mass, radius, and effective temperature values for M-dwarf stars is an active topic of debate. Differences between observed and theoretical values have raised the ...possibility that current theoretical stellar structure and evolution models are inaccurate towards the low-mass end of the main sequence. To explore this issue, we use the CHEOPS satellite to obtain high-precision light curves of eclipsing binaries with low-mass stellar companions. We use these light curves combined with the spectroscopic orbit for the solar-type companion to measure the mass, radius, and effective temperature of the M-dwarf star. Here, we present the analysis of three eclipsing binaries. We use the pycheops data analysis software to fit the observed transit and eclipse events of each system. Two of our systems were also observed by the TESS satellite – we similarly analyse these light curves for comparison. We find consistent results between CHEOPS and TESS, presenting three stellar radii and two stellar effective temperature values of low-mass stellar objects. These initial results from our on-going observing programme with CHEOPS show that we can expect to have ∼24 new mass, radius, and effective temperature measurements for very low-mass stars within the next few years.
The paper presents a method to experimentally characterize the significance of hydroelasticity for slamming loaded marine panels. The methodology is based on a large number of systematical ...experiments of slamming loaded panels from which semi-empiric expressions for the pressure distributions are derived. Finite element simulations are used to obtain rigid/quasi-static reference solutions. Hydroelastic effects are quantified by comparing deflections and strains from experiments with the corresponding non-hydroelastic reference solutions. The study shows that the largest hydro-elastic effects appear to be a time-lag effect, which however does not seem to affect the structural response magnitudes dramatically. The most significant hydroelastic effects can be expected to be close to the panel supports for very flexible structures or sandwich constructions. The results are also discussed with reference to classification rules which indicate that hydroelastic effects are small in the design of conventional ship hull structures.
•The paper considers hydroelasticity in experimental studies on slamming loaded marine panels.•Experimental data is compared with semi-empiric expression for the pressure distributions.•Time histories from experiments are compared with the corresponding rigid/quasi-static solutions.•Clear hydroelastic effects are seen relative to the rigid/quasi-static reference solutions.•Comparison with design limits from DNV highlights the range of most relevant impact situations.
ABSTRACT
We report the discovery of two mini-Neptunes in near 2:1 resonance orbits (P = 7.610303 d for HIP 113103 b and P = 14.245651 d for HIP 113103 c) around the adolescent K-star HIP 113103 (TIC ...121490076). The planet system was first identified from the TESS mission, and was confirmed via additional photometric and spectroscopic observations, including a ∼17.5 h observation for the transits of both planets using ESA CHEOPS. We place ≤4.5 min and ≤2.5 min limits on the absence of transit timing variations over the 3 yr photometric baseline, allowing further constraints on the orbital eccentricities of the system beyond that available from the photometric transit duration alone. With a planetary radius of Rp = $1.829_{-0.067}^{+0.096}$ R⊕, HIP 113103 b resides within the radius gap, and this might provide invaluable information on the formation disparities between super-Earths and mini-Neptunes. Given the larger radius Rp = $2.40_{-0.08}^{+0.10}$ R⊕ for HIP 113103 c, and close proximity of both planets to HIP 113103, it is likely that HIP 113103 b might have lost (or is still losing) its primordial atmosphere. We therefore present simulated atmospheric transmission spectra of both planets using JWST, HST, and Twinkle. It demonstrates a potential metallicity difference (due to differences in their evolution) would be a challenge to detect if the atmospheres are in chemical equilibrium. As one of the brightest multi sub-Neptune planet systems suitable for atmosphere follow up, HIP 113103 b and HIP 113103 c could provide insight on planetary evolution for the sub-Neptune K-star population.
This paper presents a novel optical technique to quantify in-plane geometric variations within dry glass fibre reinforcement materials. Samples of up to 290×450mm can be examined. Three different ...reinforcement structures have been studied; a random mat, a plain weave and a stitched bi-axial fabric. Using an empirically derived function, reinforcement areal weight has been predicted locally from a single reinforcement photograph. It was found that areal weight predictions were typically within 5% of experimentally obtained values for 25.4mm square samples. For periodically structured (woven or stitched) reinforcements, local information describing the tow orientation and geometry has been collected automatically. Manual verification of the reinforcement geometry showed good agreement with the automated technique. 3D textile models have been created within a textile modelling software that include the measured variability.
Sandwich composite materials are widely used within the marine industry, particularly as hull panels. Water impact loads, known as slamming, can be very significant for these structures, particularly ...for high-speed craft. These loadings generate local regions of high transverse shear forces near panel boundaries, which can result in transverse shear failures of core materials. The transient nature of slamming loads can cause stress rates that are high enough to affect the strength of the core material, particularly for polymeric foams. Despite the significant body of work on the constitutive behaviour and failure mechanics of sandwich core materials, there is a lack of understanding of how core materials fail in transverse shear during slamming events. There is also only very limited knowledge of how the core shear strengths measured using standardised, often quasi-static material coupon testing relate to their behaviour in a panel-slamming situation. This paper contributes in two novel areas; controlled experimental characterisation of the failure mechanics of sandwich panels subjected to water slamming to understand and quantify the strength of different polymeric core materials, comparison of the failure modes and transverse shear strength of slam-loaded sandwich panels to predictions from material coupon properties. Core types include low, medium and high elongation polymeric foams. The results demonstrate that the more ductile foams perform better as panel structures under slamming relative to their quasi-static properties compared with the more brittle cores. Prediction of the strength of a panel is shown to be highly dependent on the load distribution and whether the static or dynamic core strength is considered. The results support empirical experience that ductile foams perform well under slamming loads, and that high-elongation materials can perform better in slamming situations than predicted by their quasi-static strengths.
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