It has been suggested that spiriferide morphologies have evolved to adapt to a variety of environmental conditions. Through a computational fluid dynamics approach, we examined how the spiriferide ...original form was optimized for a lotic condition, specifically addressing the functionalization of the Devonian spiriferide brachiopod Paraspirifer bownockeri to generate passive feeding flows. The results using four models, each of which differed in the development of the spiriferide shell depression, i.e. sulcus, showed that a deeper sulcus functions to create strong spiral flows so as to align on the feeding organ inside the shell. Among the sulcus-developed models, only the mimic of the natural form could generate comparative slow flows with a stable inflow area. The fossil record of spiriferides shows a morphological trade-off between the development of the sulcus and wing form. We concluded that spiriferide shells with such a morphological combination evolved to produce various feeding strategies, resulting in diversification.
The photo-production of ϕ mesons from Li, C, Al, and Cu at forward angles has been measured at Eγ=1.5–2.4GeV. The number of events for incoherent ϕ photo-production is found to have a target mass ...number dependence of A0.72±0.07 in the kinematical region of |t|⩽0.6GeV2/c2. The total cross section of the ϕ–nucleon interaction, σϕN, has been estimated as 35−11+17mb using the A-dependence of the ϕ photo-production yield and a Glauber-type multiple scattering theory. This value is much larger than σϕN in free space, suggesting that the ϕ properties might change in the nuclear medium.
The use of polymers in the automotive industry has been growing significantly, the recycling of these materials is a major challenge nowadays, since most polymer parts comprises of different types of ...polymers, and they are joined by chemical adhesives due to their lack of good compatibility. This characteristic hampers the recycling of such polymers, and makes separation economically unfeasible, as a consequence, their final destination has ended up in landfills. In this sense, the present research developed a technique to verify the recyclability of the manufacturing waste polymer auto parts from industry processes, through the polymer layup process to obtain a composite (fiberglass, polyester fiber, polyurethane) in the form of flat panel. To achieve the objectives, the polymers were individually analyzed by differential scanning calorimetry to assist in the definition of the overlap of joined polymers, in which differentiates from the conventional method of polymer blend by extrusion. The preformed polymer was consolidated by a hot press. The polymer composites were evaluated by three-point bending test and their structure was analyzed using scanning electron microscopy (SEM). The results in flexural properties indicate a suitable consolidation strategy when compared with results in literature, which is explained by the presence of glass fiber and PET in the final composition. Through the SEM images, it enabled to observe a good interface between the glass fiber and the polyester-based polymer matrix of the wastes, directly influencing the mechanical results of the material.
Quantitative fractographic studies have become an important field to understand the fracture process. Future trends pointed out quantitative fractographic analysis as an important tool for a better ...comprehension of the damage and currently it had been focused on studies about geometric attributes of the fracture topographic surface and microstructure features. This research aimed a quantitative analysis of the cusp aspects generated in an axial fatigue test by carrying out fractographic measurements in order to know their influence on the fatigue test parameters, e.g. stress level, number of cycles, frequency, and stress ratio. Fatigue tests in tension–tension mode were undertaken in different stress levels, consequently leading to different number of cycles. Quasi-isotropic laminates were fatigue tested until the fracture, which was observed in SEM, and the hackle patterns were measured in the public domain program called Image J. The response of the laminate obeyed a cusp size pattern according to a number of cycles until the fracture was reached.
In this article, the structural behavior of co-cured composite joint (CC), co-bonded composite joint (CB), and secondary-bonded composite joint (SB) under Mode II fatigue loading was evaluated. ...Fatigue performance was evaluated in sub-critical strain energy release rate (SERR) associated with Mode II fatigue induced delamination growth onset. Fatigue tests were carried out using the three-point bending End Notched Flexure test setup for different energy ratios. The experimental results are presented in terms of SERR versus number of cycles, and the SERR threshold for no growth is determined (Gth). Fractographic analyses were performed in order to identify the main failure mechanisms related to each joining technology under Mode II. The results indicated an initial cohesive failure followed by an adhesive failure promoted by crack propagation at the interface between the adhesive and the composite adherend on SB and CB samples, through the coalescence of microcracks that promote the adhesive failure process, leading to fiber pull-out from the matrix and cusps formation in the fracture surface. These results explain the low performance behavior observed on SB and CB bonded techniques. It is worth mentioning that the results and behavior observed in this work are valid only for the laminates, adhesives, surface treatment, and environmental conditions tested herein.
Carbon fiber reinforced polymers (CFRP) structure can include dropping-off plies in order to comply with design requirements aiming at significant weight savings. However this type of discontinuity ...represents a potential source of delamination initiation and propagation which requires assessment of the mechanisms acting at the crack tip. This research investigates the influence of delamination modes I and II on the overall damage process observed in CLS specimen subjected to cyclic loads. The main contribution of this work focuses on the identification and physical interpretation of complex failure mechanisms in harness satin fabric. For this purpose a detailed fractographic analysis was carried out to qualitatively assess the surface fractures in these type of laminates. Results obtained for cyclic loaded CLS specimens were compared to analytical closed form solutions available in the literature. Results indicated that delamination front exhibited distinguishable delamination modes I and II propagating at constant mixed mode ratio (GI/GT).
Composite structures usually undergo to temperature variations in aircraft during landing/taking off and when cruising at high altitude. Under these conditions and in combination with curved ...structures, they can generate severe thermal stresses that induce delaminations. Considering the importance of studying delamination in these conditions, this research imposed an anti‐symmetrical laminate to cyclic temperature variations of 130 °C and −70 °C with the objective of inducing varied curvatures and, consequently, crack growth. Different from standardized test procedures, this test setup elastically deformed coupons without external forces and forward experimentally and numerically evaluated the strain energy release rate (SERR) during crack propagation. This procedure enabled the assessment of delamination rate (da/dN) as a function of maximum SERR. The experimental results were compared with numerical results obtained by ABAQUS Finite Element code. Despite large scatter in experimental results, a reasonable correlation between experimental and numerical results was obtained in terms of crack growth rate (da/dN) as a function of the maximum SERR.
A mechanism of generating passive feeding flow for the Devonian spiriferide brachiopod
Paraspirifer bownockeri was theoretically elucidated through fluid dynamics simulations for flow around rigid ...shells. The RANS equations were used as a turbulence model, and the unsteady incompressible flow was solved using the finite volume method. Two directions of ventral and dorsal flows were investigated as typical cases where little exchange flow occurs inside the shells. The digital model of the shell was constructed using image processing of X-ray CT images of a shell replica made by molding a polycarbonate plate to a well-preserved fossil specimen of
Paraspirifer. To examine the effect of flow velocity, three conditions of ambient flow velocity were adopted for both the ventral and dorsal flows. The pressure distribution along the gape showed that a relatively high pressure occurred around the sulcus in all simulated cases. This high pressure generated inflow from the sulcus and subsequent spiral internal flow, especially in fast ambient flows. This means that the sulcus generated the considerable pressure gradient around the gape passively and generated the stable intake of seawater and a spiral flow of water inside the shell for feeding. We conclude that the shell form of certain spiriferides could generate spiral flows so as to promote passive feeding, and the sulcus is interpreted as an important form for the passive intake of water.
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