Asymmetric double cantilever

A quantitative approach to the reinforcement of interfaces with block copolymers is necessary. Such an approach requires a way to evaluate the strength of the interface separately from any change in the morphology or microstructure of the blend. While classic fracture mechanics tests such as compact tension and double torsion could be used, the asymmetric double cantilever beam (ADCB) test used in the first such study [17] has been adopted by all successive workers to date. In this experimental geometry, shown schematically in Fig. 3, a wedge (usually a razor blade) is inserted at the interface. In some versions of the test the... 

Fig-3- Schematic of the asymmetric double cantilever beam geometry used for fracture toughness measurements... 

ABR acrylate-butadiene rubber ADCB asymmetric double cantilever beam... 

Prombut et al. [77] used carbon fibre epoxy (T7(X)/M21) laminates in asymmetric double cantilever beam (ADCB) and asymmetric mixed-mode flexure (AMMF) specimens besides standard mode I, mode II and mixed mode I/II flexure specimens in their investigation, and they complemented the experiments with numerical simulations. Although they succeeded in preventing jumps in the delamination plane and achieved reasonable crack front profiles, they concluded that more work would be needed to establish a crack propagation criterion for the 0°/45° interface. 

The experimental results that will be examined consist of studies that look at the ability of a random copolymer to improve the properties of mixtures of the two homopolymers relative to the ability of a block copolymer. The three different systems that are examined include copolymers of poly(styrene-co-methyl methacrylate) (S/MMA), poly(styrene-co-2-vinyl pyridine) (S/2VP), and poly(styrene-co-ethylene) (S/E) in mixtures of the two homopolymers. The experiments that have been utilized to examine the ability of the copolymer to strengthen a polymer blend include the examination of the tensile properties of the compatibilized blend and the determination of the interfacial strength between the two homopolymers using asymmetric double cantilever beam (ADCB) experiments. 

The first set of experiments that will be considered has examined the ability of random copolymers of styrene and methyl methacrylate to improve the interfacial strength between polystyrene and poly(methyl methacrylate). Using the asymmetric double cantilever beam technique, the researchers have found that a diblock copolymer (50/50 composition, Mw = 282,000) creates an interface with strength of400 J/m2. When utilizing a random copolymer however, it was found that the strongest interface (70% styrene, Mw =... 

PA-6/PP/PP-g-MA Melt mixing/fracture toughness measured using asymmetric double cantilever beam test/X-ray diffraction/XPS Seo and Ninh 2004... 

Amorphous PA (80)/SAN (20)/SMA Morphology/mechanical properties/ interfacial adhesion strength measured using an asymmetric double cantilever beam fracture test Cho et al. 1997, 1998... 

Asymmetric double cantilever beam and peel test experiments were completed by Eastwood et al. (Eastwood and Dadmun, 2002) to evaluate the ability of multiblock or blocky distributed chlorinated polyethylenes (bCPEs) to strengthen the PVC/POE interface compared to that of randomly distributed chlorinated polyethylene (rCPE). Additionally, the dependence of molecular weight and chlorine content of the bCPE (composition) will be evaluated to ascertain the influence of these parameters on the compatibilization process. Chlorinated polyethylenes to compatibil-ize poly(vinyl chloride) (PVC) and polyolefin elastomer (POE) blends. A series of chlorinated polyethylenes that are blocky in nature (bCPEs) with varying composition (% chlorine), and molecular weight (melt index) were used for this experiment. 

Fig. 4. Geometiy of adhesively bonded double cantilever beam (DCB) specimens. For symmetric specimens, h = H, and for asymmetric specimens, h H.

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