Failure loads for notched graphite/epoxy laminates with a softening strip

The strengths of two graphite/epoxy notched laminate systems with a softening strip were investigated. The softening strip was created by replacing the 0°-graphite/epoxy plies by a glass/epoxy composite. Experimental results indicated that the use of softening strips could significantly increase the laminate strength. Analysis was performed with finite elements developed using the classical laminated plate theory and was shown to be adequate. A simple point-stress failure criterion was used to predict the strength of notched laminates with softening strips and the result was found to be satisfactory.     

Electrical characterization of megabit DRAMs. 11. Internal testing

For pt.I. see ibid., vol.8, no.3, p.36-43 (1991). Contactless tools for testing inside dynamic RAMs, including hot-spot detection, emission microscopy, scanning laser microscopy, and submicron electron beam testing, are described. Basic principles and experimental setups are described. The utility of the techniques is assessed     

A cost-effective approach to testing

A method for assessing the differential risk of failure among a system's modules is proposed. The procedure has three components: external-risk assessment, module exposure, and module-failure likelihood. External-risk assessment is a consideration of the system's environment, almost independent of the software's details. To estimate module exposure, the model relates individual modules and their potential faults to the external-failure modes and their economic consequences by reverse-engineering the specifications and analyzing each module's expected use. To estimate failure likelihood, the method uses a reliability model. The method constitutes theoretical foundation for the cost-effective development of software that attempts to reduce the risk of failure. Managers can use the failure-risk estimates to better determine how much testing effort can be economically justified     

Thermal analysis of the architecture of old and new houses at Ghadames

The study suggests improvements in the design of new houses to conserve energy and enhance indoor thermal comfort. Summer temperature records show that a new house has an average indoor temperature of 35°C with the ambient average 31°C. The traditional house in the old city recorded 28°C for the same period. Winter temperatures in both types of houses were similar (12°C) when not occupied. Architectural features of the two houses were compared to identify those responsible for difference in the thermal performance. Larger exposed surface and window areas, higher overall heat transfer coefficient and weaker thermal coupling with the ground for the new houses seems to contribute to their inferior thermal performance.     

The glass fibre-polymer interface: II—Work of fracture and shear stresses

Pull-out experiments have been carried out on single production fibres under carefully controlled conditions. Four parameters were determined. The interfacial yield stresses, of about 9–14 MPa, were very much smaller than the shear strengths of the bulk polymers in the case of an epoxy, whether post-cured or not, and a non-post-cured polyester. Values for the work of fracture of the interface varied from 140 to 300 Jm^?2, and again were less than those of the polymer. Interface failure sometimes took place in the epoxy rather than at the fibre surface, whereas with the polyester it always took place at the fibre surface. After interface failure, pull-out was governed by friction, with maximum shear stresses of 7–10 MPa for polyester, and 21–34 MPa for epoxy, the higher values being obtained for the post-cured resins. Average frictional shear stresses were sometimes less than a half of the maximum shear stress, indicating that the fibre Poisson's shrinkage was playing an important role in the pull-out process. A silicone release agent reduced the frictional shear stresses to 2·5 MPa, with both resins.     

Calculation of the molar volume of liquid hydrocarbons

Equations are proposed for calculating the molar volume of liquid hydrocarbons used in production of surfactants. With such data, it will be possible to calculate most of the physicochemical properties of these hydrocarbons to solve many process problems. __________ Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 6, pp. 39–41, Novemmber–December, 2006.     

Empirical equations for the perforation of mild steel plates

The experimental results for the perforation energy of mild steel plate struck by flat-ended, non-deforming, cylindrical penetrators have been correlated using the principles of dimensional analysis. A correlation is presented for long penetrators. It is shown that for short penetrators a different response of the target is observed and that, at present, there are insufficient published data to produce a unifying correlation.