Curing epoxy resin test specimens

Materials Description. Three CIBA-GEIGY epoxy/hardener systems were studied Araldite 6010/906, Araldite 6010/HY 917 and Araldite 6010/972 with stoichiometries 100/80, 100/80 and 100/27, respectively. Araldite 6010 was a DGEBA epoxy resin. The hardeners 906, HY 917 and 972 were, respectively, methyl nadic anhydride (MNA), methyltetrahydro phthalic anhydride (MTPHA) and methylene dianiline (MDA). These systems were investigated previously for the matrix controlled fracture in composites (6-8). The curing cycles used can be found in (6). The ideal chemical structures of the systems are shown in Table I. Neat resins were thoroughly degassed and cast into 1.27 cm thick plates for preparation of test specimens. 

Figure 4 shows typical failure surfaces obtained from tensile tests of the co-cured single and double lap Joint specimens. In the case of the co-cured single lap Joint, as the surface preparation on the steel adherend is better, a greater amount of carbon fibers and epoxy resin is attached to the steel adherend. Failure mechanism is a partial cohesive failure mode at the C ply of the composite adherend. In contrast with the co-cured single lap joint, failure mechanism of the co-cured double lap joint is the partial cohesive failure or interlaminar delamination failure at the 1 ply of the composite adherend because interfocial out-of-plane peel stress... 

Electrical Data. The electrical properties of cured specimens of the epoxy resin, containing various quaternary phosphonium compounds, were obtained on 2 in. diameter discs (0.125 in. to 0.25 in. thick) using standard procedures (ASTM D150-65T). In these tests, the power factor (100 x tan 6) and dielectric constant (e ) data were usually measured at 150 C (and a frequency of 60 Hz) on resin samples which had been cured for 16 h at 135 C + 5 h at 150 C. 

Continuous scans of modulus versus temperature utilizing the DuPont Dynamic Mechanical Analyzer (DMA) has provided a comparison of the high temperature service capabilities of radiation-cured experimental formulations of a vinyl-modified epoxy resin. Shell Epocryl-12. These scans were compared to data obtained when the same materials were applied as adhesives on aluminum test panels, radiation-cured with an electron beam, and lap shear strength tested at discrete temperatures. The DMA instrument utilizes a thin rectangular specimen for the analysis, so specimens can be cut from blocks or from flat sheets. In this case the specimens were cured as sheets of resin-saturated graphite-fibers. The same order of high temperature stability was obtained by each method. However, the DMA method provided a more complete characterization of temperature performance in a much shorter test time and thus, it can be very useful for quick analyses of formulation and processing variables in many types of materials optimization studies. The paper will present details of this study with illustrations of the comparisons. 

In Ref [62], the studied object was an epoxy polymer on the basis of resin UP5-181, cured by iso-methyltetrahydrophthalic anhydride in the ratio by mass 1 0.56. Testing specimens were obtained by the hydrostatic extrusion method. The indicated method choice is due to the fact, that high hydrostatic pressure imposition in deformation process prevents the defects formation and growth, resulting to the material failure [64]. The extrusion strain was calculated according to the Eqs. (14.10) and (4.39) and makes up 0.14, 0.25, 0.36, 0.43 and 0.52. The obtained by hydrostatic extrusion specimens were annealed at maximum temperature 353 K during 15 min. 

The test specimens were prepared by adding a desired amount of the filler (powders of non-metals [81] and met [82] with partides sizes between 20 and 150 microns) to the base epoxy resin/hardener formulation which was subsequently cured at 373 K (1 h) post-cured at 453 K (2 h). The heat conduct-... 

The SWNT ropes used were the same as those used for bundle strength measurements discussed earlier. The matrix material used was Epicote 1006 epoxy resin, a room temperature curing system. 32 dog-bone SWNT/epoxy specimens with dimensions of 40 mm x 3.5 mm x 0.4-0.6mm were obtained. The gauge length of die specimens was about 15 mm, and the length of SWNT ropes embedded in the epoxy was about 20 mm. Details of the fabrication method can be foimd elsewhere. The volume fraction of SWNT ropes in the composite was controlled widiin die range of 0.1-0.9%. Specimens were cyclically tested by an Instron 8800 Microforce Tester under tension-tension at 5 Hz, using a sinusoidal wave function at R ratio (ratio of minimum to maximum cyclic stress) of 0.1. 

The results described in this paper were all obtained from tests on E-glass reinforced composite materials produced by hand lay-up. This is the manufacturing route most frequently used for marine structures. For the majority of the tests reported here the E-glass fibres were either quasi-unidirectional (250 g/m with 1 g/m of polyester fibres bonded in the 90° direction to keep the UD fibres in place) or stitched quadrlaxial (0/45/907-45° 1034 g/m ) cloths. The same uniaxial ply is used in both cloths. The resin is based on DGEBA epoxy (SRI500) with an amine hardener (2505) from Sicomin, France. All epoxy specimens were post-cured at 90°C for 6 hours. Some results are also shown for a woven glass (0/90° 500 g/m ) reinforced isophthalic polyester for comparison, as this is the traditional marine... 

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