Composite notched strength

With decreasing temperature the alloys exhibited some decrease in notch strength and notch yield ratios the amount of the decrease varied with composition and temper. The plots of the ratios as functions of temperature in Fig. 2 are smooth curves, with no suggestion of abrupt transitions in fracture behavior. The data for those alloys that were tested only at temperatures to —320°F may be compared readily with those for alloys tested down to —423°F, with little likelihood of misinterpretation. 

Composition Tensile strength, MPa Notched Izod, J/m Flexural strength, MPa Melt flow index, g/10 min... 

M T Kortschot and P W R Beaumont, Damage mechanics of composite materials n - A damage-based notched strength model . Compos Sci Technol 1990 39 303-326. 

Hitchen SA, Ogin SL, Smith PA, Soutis C, The effect of fibre length on fracture-toughness and notched strength of short carbon-fibre epoxy composites. Composites, 25(6), 407-413, 1994. Kishimoto K, Notomi M, Koizumi T, Fracture toughness of short carbon-fibre-reinforced thermoplastic pol5mide. Engineering Fracture Mechanics, 49(6), 943 et seq, 1994. 

K.S. Ahmed, S. Vijayarangan, and A.C.B. Naidu, Elastic properties, notched strength and fracture criterion in untreated woven jute-glass fabric reinforced polyester hybrid composites. Mater. Des. 28, 2287-2294 (2007). 

Class Resin Type Composition Impact Strength, Notched/Unnotched 0/cm)... 

Composition Wt% Glass in Composite Tensile Strength (MPa) Tensile Modulus (GPa) Notched Charpy Impact Strength (J/mm ... 

These values are determined by experiment. It is, however, by no means a trivial task to measure the lamina compressive and shear strengths (52,53). Also the failure of the first ply of a laminate does not necessarily coincide with the maximum load that the laminate can sustain. In many practical composite laminates first-ply failure may be accompanied by a very small reduction in the laminate stiffness. Local ply-level failures can reduce the stress-raising effects of notches and enhance fatigue performance (54). 

Typical S-N (stress versus number of cycles) curves for various metals and composite materials are shown in Figure 6-4 [6-3]. The boron-epoxy composite material curve is much flatter than the aluminum curve as well as being flatter than the curves for any of the metals shown. The susceptibility of composite materials to effects of stress concentrations such as those caused by notches, holes, etc., is much less than for metals. Thus, the initial advantage of higher strength of boron-epoxy... 

Table 8 Effect of Composition of TMTD Curing System on the Charpy Notched Impact Strength (ai<) for 85/15 and 80/20 PP/EPDM Blends...

A typical unsaturated unreinforced polyester resin has an extremely low notched Izod impact strength. The addition of fibrous glass can change this extremely brittle material into a high impact strength composite. The same phenomenon occurs with some brittle thermoplastics, such as polystyrene and styrene—acrylonitrile. 

Noninstrumented Izod Testing. The impact strength, reported in joules per meter of notch, was measured at temperatures between 25° and — 30°C. The samples were cooled to the test temperature using a Lauda Kryostat and equilibrated in the Kryostat for at least one and one half hours prior to testing. Five to seven seconds were required to remove a sample from the Kryostat, mount, and perform the Izod impact test. Ten samples of each composition were tested at each temperature. 

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