Low Velocity Impact Behavior of Glass Filled Fiber-Reinforced Thermoplastic Engine Components
This paper concerns automotive parts located underneath the engine and in particular the engine oil pan. Classically made of stamped steel or cast aluminum, new developments have allowed the manufacture oil pans with polyamide 66 reinforced by 35% weight of short glass fiber. However, polyamides have some limitations and the most significant is their response to localized impact loading. The nature of the impact considered here is of a typical stone collected from the road and projected into the oil pan. Low velocity impact investigations were carried out using a gas gun and drop weight tower. The study shows that the design of the oil pan has a significant contribution in the shock absorption. In addition to the material properties, the geometry and the ribbing both cleverly combined, increase the impact resistance of the component significantly. Areas of oil pan design improvement have been identified and conclusions drawn.
Fracture toughness and impact behaviour of glass-fibre-reinforced polyamide 6,6 injection mouldings
Abstract The fracture toughness of injection-moulded long-glass-fibre-reinforced polyamide 6,6 (average fibre aspect ratio in mouldings, l/d ≈ 55) with fibre weight contents of 50 and 60 % was studied and compared with that of short-glass-fibre-reinforced polyamide 6,6 (l/d ≈ 20). Toughness was measured by using Mode I compact-tension specimens cut from the mouldings and also by means of instrumented drop-weight impact tests. The addition of fibres to a polyamide 6,6 matrix led to an improvement of fracture toughness. The improvement was marginally greater in the long-fibre grades. Fracture toughness values were dictated by the average in-plane fibre orientation angle ahead of the crack front and fibre length, particularly for the long-fibre grades. Instrumented drop-weight impact tests indicated brittle fracture for unreinforced polyamide 6,6, causing possible catastrophic shattering into several pieces. Short-fibre and long-fibre materials both remained intact after impact, with smaller dimensions of the damaged area for the long-fibre materials. Crack initiation force and total energy values were increased by 25–37% and 300–600%, respectively, with the inclusion of glass fibres. Negligible differences in these values were observed between the long- and short-fibre grades and with the long-fibre content increasing from 50 to 60% w/w.
Right coronary artery stenosis associated with tricuspid valve ring annuloplasty
A 70-year-old man with severe symptomatic functional mitral valve regurgitation underwent successful mitral valve repair combined with tricuspid valve ring annuloplasty. Pre-operative coronary angiography (CAG) showed no significant stenosis. One-and-a-half years later, the patient presented with an acute exacerbation of heart failure. Repeat CAG demonstrated tight stenosis in the right coronary artery (RCA) with arterial kinking that corresponded to the same point as the stenosis where the RCA is the closest to the tricuspid valve ring. The new lesion probably occurred as a consequence of the tricuspid valve ring annuloplasty.