Microstructure and Mechanical Aspects of Multicrystalline Silicon Solar Cells

Due to pressure from the photovoltaic industry to decrease the cost of solar cell production, there is a tendency to reduce the thickness of silicon wafers. Unfortunately, wafers contain defects created by the various processing steps involved in solar cell production, which significantly reduce the strength of the wafers and cells. Therefore, a...

Effect of cooling rate on interlaminar fracture energy and shear strength of APC-2 laminates

The effect of cooling rate on some mechanical properties of APC-2/AS4 composite was investigated over the range between 1 and 70° C/min. Preconsolidated unidirectional laminates were reprocessed in a hot platen press at controlled cooling rates. Double Cantilever Beam specimens and End Notch Flexure specimens were used to determine the mode I...

The effects of strain rate and temperature on the fracture behaviour of three structural adhesives

The effects of strain rate and temperature on the fracture behaviour of three structural adhesives (Redux 775, Metlbond 328 and EC 2216) were investigated using Double Cantilever Beam specimens. The test results were presented as critical elastic energy release rate data (G) to investigate whether this parameter could be used to characterize me...

Residual strength of bonded stiffened panels: prediction and experimental verification

This report presents results of residual strength calculations, carried out on cracked panel configurations of various designs and provided with bonded stiffeners. The calculations were carried out using the computer program BOND. The results of these calculations are compared with results of residual strength tests, performed on panels of...

Comparison of fracture toughness in titanium alloys IMI 550 and IMI 551

Fracture toughness tests on two high strength titanium alloys, IMI 550 and 551, showed that the higher strength alloy, IMI 551, had a much lower toughness. The alloys were very similar in microstructure and fracture mechanisms. A number of model formulations for predicting fracture toughness were compared with the experimental results. This...

Residual strength characteristics of composite reinforced stiffened panels

Vacuum fatigue fracture in titanium alloy plate

Aluminium alloys for advanced structural applications in transport aircraft

This paper concisely reviews and discusses (1) metallurgically cleaner alloys like -2124, 2048 and 7475, (2) potential application of 7000 series alloys in tension panels, (3) development of high strength stress corrosion resistant thick section materials like 7010, 7049 and 705O, (4) powder metallurgy 7000 series alloys with high strength and...

The effect of sheet edge working on the fatigue life under flight-simulation loading

Fatigue tests under flight-simulation loading have been performed on unnotched Alclad 2024-T3, anodised 2.0 mm thick sheet specimens, manufactured according to several machine-shop processes applied in the air craft industry. From the results it appears that milling is preferable to stamping. Rounding off the edges is also advantageous. The...

Residual strength properties of carbon/epoxy composite material

Fatigue tests on unidirectional Ca/ep composite material have been performed to investigate whether previous fatigue loading did influence the residual static strength. Residual strength tests were carried out on (0, ± 45)2s and (± 45)2s laminates, while for the (O, ± 45)2s laminate the influence of previous tensile fatigue loading on the...

Effects of crack plane orientation transitions on flight simulation fatigue crack propagation in a high strength aluminium alloy (7050)

The effects of flat to slant fracture transitions on flight simulation fatigue crack propagation in specimens of 7O5O aluminium alloy forgings are discussed. For specimens containing flat, shearlipped, or full slant fractures at similar crack lengths the crack resistance (R curve) approach appears to provide an explanation for differences in the...

Residual strength of the aluminium alloy 7475-T76 at low temperatures

Residual strength tests have heen performed, on 300 mm wide centrecracked panels of various thicknesses, at room temperature and at -50 C. During the tests, stable crack growth was filmed and recorded with the electric potential method. Fracture toughness was determined using the method of Feddersen.

Residual strength data of riveted panels with different stiffener configurations

Residual strength tests were carried out on center-cracked panels with a 2024-T3 or 7075-T6 skin and provided with eccentric stiffeners of practical design. The stiffeners were riveted to the skin. The material of the stiffeners was 7075-T6. In some cases the stiffeners were combined with Ti-alloy crack stoppers. On the basis of the test results...

Scanning electron microscopy of fracture surfaces of carton composite materials

A microscopic study has been performed on carbon composite fracture surfaces, using the Scanning Electron Microscope (SEM). It appears that the SEM is a useful tool to examine the fracture surface characteristics of composite materials failing under different loading conditions.

Heat treatment studies of aluminium alloy type 7050 forgings. Interim report no. 2: The effect of heat treatment on a variety of engineering properties

The effect of variety of heat treatments on various engineering properties was studied with the aim to derive an optimum heat treatment. The engineering properties comprised Vickers hardness, short-time tensile strength, fatigue crack propagation resistance, fracture toughness and stress corrosion resistance. The test results were compared with...

Rate effects on residual strength of flawed structures and materials

The literature is reviewed with respect to: - tests conducted to investigate crack re-initiation under dynamic load and arrest of a running crack - metallurgical sources of rate effects - available data for aerospace engineering materials - mechanical sources of rate effects, i.e. dynamic crack tip stresses and kinetic energy effects Conclusions...

Fracture toughness and fatigue properties of the new aluminium alloy 7475-T76

Residual strength tests have been performed on 610 mm wide centre cracked panels. During the tests, stable crack growth was filmed and crack opening displacements were measured. Fracture toughness was determined using the method of Feddersen. Flight simulation fatigue tests were carried out to investigate the crack propagation properties. A...