4.1.2 Thermal propertiesįillers usually have a thermal conductivity about 20 times higher than plastics, and the specific heat is about 50%. The high aspect ratio of glass fibres means that they can provide the greatest improvement in mechanical properties. Talc offers many options because it is capable of many different modifications and surface treatments. Fibre-like wollastonite particularly improves the flexural modulus while cube-shaped calcium carbonate can improve both impact strength and modulus. Impact strength and flexural modulus are the mechanical properties that can most be improved by careful selection of mineral fillers, and the shape of the particle is important. John Murphy, in Additives for Plastics Handbook (Second Edition), 2001 4.1 Effect of Fillers 4.1.1 Mechanical properties Large deflection is reached before the final failure when fibre rupture occurs. 3.26(b)) and the compressive surface ( Fig. Delamination along the fibre strands can be observed on both the tensile surface ( Fig. In contrast, laminates with all fibres oriented at ±45° to the specimen length direction show ductile failure, as in compression. 3.26 for a biaxial specimen tested along a fibre direction. This typical failure mode can be observed in Fig. The delamination zone starts at the middle of the specimen where the bending moment is maximum, then propagates outwards until significant fibre rupture occurs at the middle section on the tensile surface. All the laminates tested along a fibre direction show brittle failure, generally by outer ply delamination on a tensile surface. 3.25, exhibit less non-linearity than the tensile and compressive responses. The flexural load–deflection responses, shown in Fig. The flexural strengths of all the laminates tested are significantly higher than their tensile strengths, and are also higher than or similar to their compressive strengths. The flexural modulus is similar to the respective tensile modulus, as reported in Table 3.1.
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