Laminate testing Thermal properties

It was decided to febricate these parts from epoxy-glass laminates, as their properties are more than adequate for the intended application. In order to select between NEflA grade G-10 and G-11 types of epoxy-glass laminates, thermal shock tests were performed. Samples of the two types of laminates 2.5cm thick were obtained from the Micarta Division of Westinghouse Electric Corporation. 

Thermal Properties. The important thermal properties of a laminate are the glass transition temperature, the coefficient of thermal expansion, the time to delamination, and the decomposition temperature. - These properties quantify the material s reactions to extreme temperatures and so are indicator s of the materials suitability for a particular reflow profile and residual capacity for withstanding heat input (such as rework or hot use environments). Tgalone is insufficient to predict a materials response to LFA tenperatures. In fact, since each test measures a different response to temperature, all the tests together provide a broad determination of suitability to a particular use. 

Thermal residual stresses are inherent to fibre reinforced composites due to the heterogeneity of the thermo-mechanical properties of their two constituents. Such stresses build up when composite structures are cooled down from the processing temperature to the test temperature. Residual stresses will be present on both a fibre-matrix scale (micro-scale), and on a ply-to-ply scale (macro-scale) in laminates built up from layers with different orientations. It is recognised that these stresses should be taken into account in any stress analysis. 

The flexibilized and unreinforced resin was also tested at 20°C. Moisture absorption in the unreinforced resin and in the Navy GRP was consistent with Pick s law. The Navy GRP showed the least total takeup of water. The epoxy laminates deviated from ideal Fickian behaviour. At 20°C, both the glass and polyester fibre laminates reached a peak mass and then decreased, suggesting that some material was being leached out into the water. The mechanical properties were determined by dynamic mechanical thermal analysis (DMTA). All the laminates experienced a reduction in the effec-... 

The above-mentioned thermomechanical models only consider the elastic behavior of materials. Boyd et al. [13] reported on compression creep rapture tests performed on unidirectional laminates of E-glass/vinylester composites subjected to a combined compressive load and one-sided heating. Models were developed to describe the thermoviscoelasticity of the material as a function of time and temperature. In their work, the temperature-dependent mechanical properties were determined by fitting the Ramberg-Osgood equations and the temperature profiles were estimated by a transient 2D thermal analysis in ANSYS 9.0. 

The effect of low temperatures on various laminates is shown in Fig. L.3. Tensile properties generally improve as the temperature is reduced. However, impact properties may be degraded. Certain adhesives show a similar trend regarding increase in tensile strength and reduction in impact strength as the test temperature is reduced. However, with adhesives in metal joints, many of the problems that occur at lower temperatures are due to thermal expansion differences between the substrate and the adhesive rather than the cohesive properties of the adhesive itself. 

In this paper, the thermal and mechanical characteristics of balsa wood and balsa wood laminates are reviewed, and it is shown that "composite" mechanics that have been developed for the class of synthetic fiber-reinforced plastic (SFRP) materials may be useful for describing the density and direction—dependent mechanical properties of balsa wood in bulk or laminated form. It may be asked whether such advanced analytical methods, perhaps combined with specially developed methods of test, could be used effectively towards developing more applicable QA/QC procedures that will clearly qualify balsa wood as a structural material in applications where strictest code compliance is a necessity. This question has prompted the following review and discussion. 

Board material The FR-4 versus polyimide board material properties did not have a significant impact on trace temperature, which is determined primarily by the thermal conductivity of the dielectric laminate material construction. Table 16.2 lists measured thermal conductivity values for each of the test boards.The column labeled kz presents values through the thickness of the board and represents the resin thermal conductivity.The values in columns kx and ky are in-plane and the difference is attributed to the influence of the glass fiber. 

Laminates based on Rhone Poulenc s Keramid 601 polyimide resin are fabricated in a conventional laminating press, and processed in a manner similar to that used for epoxies but with an extended cure cycle or post-cure. The room-temperature mechanical and electrical properties are similar to epoxy laminates, as shown in Table 9.4. At elevated temperatures, the polyimides exhibit exceptional stability. In particular, the thermal coefficient of expansion in the Z axis does not change significantly up to approximately 240°C, as shown in Fig. 9.11. Exhaustive tests have shown that polyimide-based multilayer boards can withstand repetitive thermal cycling at elevated temperatures (>150°C) without cracking of plated through holes. Similar excellent results were also obtained in solder shock tests (10 s at 288°C in molten solder). The thermal stability of these materials is retained at temperatures of approximately 200°C for continuous exposure in air, which has qualified them for military applications. 

The combination of these properties and respective test results provide the information necessary to select a laminate material with the desired thermal capacity. Depending on the laminate selected, additional time may be added to the production process, an unappealing thought for designers and quick-turn PCB manufacturers. 

Solid residue was obtained by two processes to reduce discarded tires pyrolysis and thermal shock. Techniques such as X-ray, FTIR, TGA and SEM were used to characterize the samples. Two types of polyethylenetherephtalate, PET (virgin and recycled) were analysed physicochemical and mechanically to be used as matrix. A composite material was manufactured by employing a Brabender mixing chamber in order to nse the grannies as fdler on PET at different concentrations. The mixed material was laminated and tension test were undertaken in samples to acquire the mechanical properties. Studies of ffactography were performed to understand the failure mechanics. 

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