Fracture surface morphology examination

Fracture Surface Morphology. Although full details will be published separately, preliminary observations of fracture surface morphology were made on an ETEC scanning electron microscope, using specimens that had been coated with gold and carbon prior to examination. 

Fracture Surface Morphology. While a complete study of fracture surface morphology and the micromechanisms of failure is still in progress, preliminary examination revealed major differences between the modified and neat PVC s. These are now being interpreted in order to elucidate the micromechanism of failure. 

The fracture surface morphology was examined using a scanning electron microscope (Oxford-XL30 PhUips) for specimens coated with gold. The specimens were cleaned with water using a Bran Sonic 52 and dried in an oven at 30 °C for 30 minutes before coating for SEM. 

The final morphology of specimens cured at different curing temperatures and composition was observed by SEM. Fractured surfaces of postcured specimens prepared in liquid nitrogen, were etched with methylene chloride before examining by SEM. 

Ideally, rubber toughening should be accomplished without substantial sacrifices in modulus. For each modified resin, flexural and Young moduli and plane-strain fracture toughness were determined. Examination of various fracture surfaces by scanning electron microscopy showed the effects of modifier composition on the morphology of these multi-phase materials as well as the prominent features of the fracture process. 

Samples in the SEM can be examined "as is" for general morphology, as freeze fractured surfaces or as microtome blocks of solid bulk samples. Contrast is achieved by any one or combination of the following methods ... 

Figures 2a, 2b, 2c, and 2d represent the morphology of the 25/75 (PC-PST) blend. PST forms the continuous phase and the dispersed spherical PC particles show some aggregation (Figure 2a). From the transmission electron micrographs (Figures 2b and 2c) it can be seen that small PST particles are present in the dispersed PC phase. Examination of the etched fracture surface by scanning electron microscopy reveals depressions of completely removed PC particles as well as spheres with dark periphery because of partial hydrolysis of PC (Figure 2d).

Failure Investigation. The clamp was nonmagnetic and the stamped identification on the side of the U-shaped shells indicated that they were fabricated from forged 304 austenitic stainless steel. Visual examination of the fracture surfaces revealed they were entirely brittle and exhibited a very coarse fracture morphology. Liquid penetrant inspection revealed the presence of additional cracks in the fractured half of the clamp. There was no cracking present in the high-strength steel fasteners. 

Unfortunately the surface of the complexed sample cannot be replicated and examined by electron microscopy because the solvents normally used perturb the complex by introducing artifacts. However scanning electron micrographs of these fracture surfaces indicate that the morphology of the original polymer is modified considerably by the I2-KI treatment—a fact consistent with the wide angle x-ray and other evidence. It has been pointed out elsewhere (11) that thin films and fibers of complexed polyamides are very pliable and often putty-like when first removed from the complexing solution this fact is consistent... 

The morphology of a small particle size, toughened system has been further explored by examining the fracture surfaces of the stressed tensile bars. An electron photomicrograph of a replica of this surface showed a deformation band extending diagonally (Figure 6). The rubber par-... 

To examine craze microstructure, and to study the effect of molecular variables on craze morphology, the method described by Kramer was followed. Samples of polymers were cast in the form of thin films, strained in tension while bonded to carbon-coated grids, and examined in the transmission electron microscope either before or after staining. The TEM observations were made with an Hitachi HU-11 A unit or with a JEOL JEM-IOOCX unit, operating usually at 75-80 kV. Fracture surfaces of many bulk samples were coated with a thin layer of gold-palladium and examined by an Etec scanning electron microscope. 

Morphology. The morphology of the fracture surface of the two-phase epoxy thermosets was examined by scanning electron microscopy (SEM, Amray model 1000B). SEM specimens were sputter-coated with a thin film of gold. 

Transmission electron microscopy (TEM) was used to study the morphology of the cross-linked matrix and to determine the size of the rubber domains. Specimens were microtomed and exposed to osmium tetroxide vapor to stain the rubber-rich portions of the network. The fracture surfaces of specimens were coated with gold and examined with a scanning electron microscope (SEM). 

The relationship between the impact properties and morphology in ICP has been studied extensively. For example. Tan et al. (4) and Cai et al. (5) examined the effect of morphology on the impact strength using ICP samples with similar ethylene content, molecular weight, and molecular weight distribution. A typical SEM micrograph of fractured surface ICP specimens after the impact test at — 20°C is shown in Fig. 8.3. 

An ISI model 60A scanning electron microscope was used to examine the morphology of the fracture surfaces. Both the neat resins and the composite laminates were notched at room temperature with a razor blade. The samples were then Immersed in liquid nitrogen and fractured in air Immediately after removal from liquid nitrogen. The neat resins were fractured by bending the samples with pliers and the laminates were fractured along the fiber by opening up the notched cracks with pliers. 

Isayev and Modic (1987b) reported that injection molded and extruded blends of an HB A/HNA LCP and PC containing greater than 25 wt% LCP had spherical LCP domains dispersed in the PC matrix. However, blends with 10 % LCP had a fibrillar morphology. Pracella et al. (1987) reported a similar observation when they examined the morphology of blends of PBT with another LCP. The fracture surfaces of blends that contain up to 50 wt% LCP revealed the presence of rod-like structures of the LCP component oriented perpendicular to the fracture plane. For blends that contain more than 50 wt% LCP, the morphology was homogeneous and LCP domains were not observed. 

SEM analysis was carried out to examine the fracture and bond characteristics of hardened concretes produced from different sandstone aggregates. The concrete samples for SEM analysis were dried at 105 C for 24 h. The dried concrete samples were carefully broken. Ereshly fractured surfaces were coated with gold in a vacuum evaporator. They were examined by a Scanning Electron Microscope (SEM) to determine morphological and minera-logical features. SEM images were also fitted with Electron Dispersive Spectroscopy (EDS). 

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