Morphology-induced fatigue crack arresting in carbon fibre sheet moulding compounds

Carbon Fibre Sheet Moulding Compounds (CF-SMCs) are tow-based composite materials. Interrupted fatigue tests, combined with computed tomography, were performed here to investigate the damage mechanisms in high in-mould flow CF-SMC. The tow-based microstructure created obstacles for fatigue damage propagation, increasing the CF-SMC’s resistance against cyclic loading. Failure is shown to nucleate inside the tows, but inter-tow crack propagation tends to be hindered by the presence of the other tows. Tows oriented perpendicularly to the initial fatigue crack stop the crack itself, showing an intrinsic crack arrest mechanism. Additionally, pre-existing manufacturing cracks or voids do not propagate at all. As a result, flatter slopes of the SN diagrams were observed for CF-SMC than for other carbon or glass fibre composites with short, long and even continuous fibres

External Morphology and Ultra-Structure of Eggs and First Instar of Prepona Laertes Laertes (Hübner, [1811]), with Notes on Host Plant use and Taxonomy

The external morphology and the tegument ultra-structure of Prepona laertes laertes (Hübner, [1811]) (Lepidoptera: Nymphalidae: Charaxinae) eggs and first instar larvae feeding on Inga spp. (Fabaceae) in a forest fragment in Joinville, Santa Catarina, Brazil, are described. Descriptions of the morphology with illustrations are presented, based upon observations through scanning electron microscopy and stereoscopic and optic microscopes attached to a camera lucida. Descriptions and illustrations of the head capsule, chaetotaxy, tegument, and setae are presented. The taxonomy, morphological characters, and host plant use of Prepona laertes immature stages are discussed

Biology of Morpho polyphemus (Lepidoptera: Morphidae) in El Salvador

Volume: 80Start Page: 18End Page: 4

Carbon fibre sheet moulding compounds with high ine-mould flow: Linking morphology to tensile and compressive properties

In-mould flow during manufacturing of Sheet Moulding Compounds (SMCs) heavily affects the material microstructure and its mechanical properties. This influence is studied here for carbon SMCs on panels compression moulded with limited charge coverage. The high in-mould flow caused severe in-plane tow distortions, while their planarity was preserved. Flow induced fibre orientation plays a paramount role in the material failure, whereas local manufacturing defects had no discernible influence. The properties difference between specimens with preferential orientation of 0° and 90° was 150% for tensile stiffness, 260% for tensile strength, 120% for compressive stiffness and 32% for compressive strength. The compressive strength and failure strain for 45° and 90° specimens were higher than those for tension, and comparable for 0° specimens. Compressive and tensile moduli were similar for specimens with the same orientation. A clear link between SMCs manufacturing and mechanical performance is highlighted, together with its implications on structural design

De novo topology optimization of total ossicular replacement prostheses

Conductive hearing loss, due to middle ear pathologies or traumas, affects more than 5% of the population worldwide. Passive prostheses to replace the ossicular chain mainly rely on piston-like titanium and/or hydroxyapatite devices, which in the long term suffer from extrusion. Although the basic shape of such devices always consists of a base for contact with the eardrum and a stem to have mechanical connection with the residual bony structures, a plethora of topologies have been proposed, mainly to help surgical positioning. In this work, we optimize the topology of a total ossicular replacement prosthesis, by maximizing the global stiffness and under the smallest possible volume constraint that ensures material continuity. This investigation optimizes the prosthesis topology in response to static displacement loads with amplitudes that normally occur during sound stimulation in a frequency range between 100 Hz and 10 kHz. Following earlier studies, we discuss how the presence and arrangement of holes on the surface of the prosthesis plate in contact with the umbo affect the overall geometry. Finally, we validate the designs through a finite-element model, in which we assess the prosthesis performance upon dynamic sound pressure loads by considering four different constitutive materials: titanium, cortical bone, silk, and collagen/hydroxyapatite. The results show that the selected prostheses present, almost independently of their constitutive material, a vibroacustic behavior close to that of the native ossicular chain, with a slight almost constant positive shift that reaches a maximum of ≈5 dB close to 1 kHz. This work represents a reference for the development of a new generation of middle ear prostheses with non-conventional topologies for fabrication via additive manufacturing technologies or ultraprecision machining in order to create patient-specific devices to recover from conductive hearing loss

Mid-term evaluation of the Regional Project on Coffee Pest Control (IICA-PROMECAFE-AID/ROCAP 596-0090).

Posee edición en inglés y españolPresenta un informe de la evaluación realizada sobre la marcha (agosto-setiembre de 1984) del Proyecto Regional de Control de Pestes del Café, ejecutado en el marco del convenio IICA/PROMECAFE-USAID-ROCAP No. 596-0090. Los países participantes en este proyecto son: Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica y Panamá. Las actividades evaluadas se enmarcaron dentro de los siguientes componentes del proyecto: (1) introducción de cafetos de alto rendimiento resistentes a la roya; (2) biología, epidemiología y control de la roya del café; (3) biología, epidemiología y control de la broca del café; (4) análisis residual para el control e inscripción de pesticidas; (5) capacitación de personal técnico y auxiliar; (6) desarrollo, adaptación y transferencia de tecnologías apropiadas para el cultivo del café; y (7) desarrollo de un sistema regional de información y banco de datos. Se incluye además algunas recomendaciones sobre la participación de los organismos regionales que cooperan con el proyecto, especíificamente OIRSA y CATIE. También presenta un análisis sobre el período, recursos y prospección de necesidades del proyecto. Finalmente, enumera las conclusiones y recomendaciones generales presentadas por la misión evaluadora

Ultra-low power microwave CHFET integrated circuit development

This report summarizes work on the development of ultra-low power microwave CHFET integrated circuit development. Power consumption of microwave circuits has been reduced by factors of 50--1,000 over commercially available circuits. Positive threshold field effect transistors (nJFETs and PHEMTs) have been used to design and fabricate microwave circuits with power levels of 1 milliwatt or less. 0.7 {micro}m gate nJFETs are suitable for both digital CHFET integrated circuits as well as low power microwave circuits. Both hybrid amplifiers and MMICs were demonstrated at the 1 mW level at 2.4 GHz. Advanced devices were also developed and characterized for even lower power levels. Amplifiers with 0.3 {micro}m JFETs were simulated with 8--10 dB gain down to power levels of 250 microwatts ({mu}W). However 0.25 {micro}m PHEMTs proved superior to the JFETs with amplifier gain of 8 dB at 217 MHz and 50 {mu}W power levels but they are not integrable with the digital CHFET technology