In this paper, the influence of anisotropy of dynamic and fracture properties on the fracture mechanism, induced by the anisotropy of a layer structure formed by three-dimensional stresses developed by round tips is investigated. Analysis is done by studying fatigue fracture patterns and dynamic properties of notched samples (simple dynamic model). (1) When the anisotropic layer structure is formed up to some critical degree, cracks generate on the sample surface perpendicular to principal tension stresses, that is, perpendicular to the layer structure. Then the cracks grow parallel to the layer structure as fatigue progresses. Consequently, lamellar flaking appear on the surface and yield striped patterns of fatigue fracture. (2) Close correlations are recognized between the stresses developed as cracks propagate from a perpendicular direction to a direction parallel to the layer structure and the degree of fatigue (represented by the ratio of fracture surface energies). As the anisotropic properties of the structure and the degree of fatigue become pronounced, lamellar fractures come to be easily generated by low stresses.

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Fracture surface patterns caused by the fatigue due to three-dimensional stresses are different from those by the fatigue due to one-dimensional stresses because of lamellar flaking patterns formation in the former fatigue. But, in both cases, when internal-structures are changed and the changing has progressed to some extent, rubber molecular chains are broken and initial cracks are generated perpendicular to principal tensile stresses. In this study, assuming that the tendencies of the life curves for one-dimensional and three-dimensional stresses are the same, the life curve (logK_β-logL_β) is expressed as an approximation of the life curve (logK-logL) by shifting α along the normalized life axis and β along the normalized stress axis. The life curve (logK_β-log L_β) is a normalized curve given by normalizing the maximum tensile stresses and life time in three-dimensional stresses by dividing them respectively by the fracture stresses and the fracture time in one-dimensional stresses, and logK-logL curve is a normalized life curve in one-dimensional stresses, and α and β are the ratios of the fracture time and stress in one-dimensional stresses to those in three-dimensional stresses.

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The effect of fiber length on the mechanical and dynamical properties of PET short fiber-CR composite was investigated. The extension and tensile strength of the composites filled with fibers of length under 2mm decreased with increasing the fiber content, while the tensile strength of the composites filled with fibers of length over 2mm changed from decrease to increase and their extension decreased noticeably at about 5vol% of the fiber content. Stress-strain curves of the composites showed that the composites filled with fibers under 2mm length yielded and that the tensile stress of the composites filled with fibers of length over 4mm increased linearly to failure without yield. The composites filled with fibers of 2mm length yielded at a low fiber content and failured at a high fiber content. The dynamic storage moduli of the composites were determined as following equations: E′_c=E′_r+0.34•L• (E′_f-E′_r)•V_f at L<3.1mm and E′_c=E′_r+(E′_f-E′_r)•V_f at L>3.1mm, where E′_c, E′_r and E′_f are dynamic storage moduli of composite, CR, and PET fiber, L and V_f are length and volume fraction of the fiber.

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In order to reveal the fixing phenomenon between vulcanizates and metals and develop the preventing method, the fixing test and the determination of fixing strength were investigated. The fixing test was carried out by lieving a compression apparatus with fixing samples in an Atempter of 80°C and 90% relative humidity. The compression apparatus was used to compress the fixing samples which brought into contact with vulcanizates and metal plates. The fixing strength of the obtained fixed samples was measured by using an Autograph and expressed as a shearing stress. The contact modes of vulcanizates and metals had a great effect on the measuring sensitivity, the standard deviation, the measuring limit and the easiness of measurement in the determination of fixing strength. The fixing strength increased up to a load of 0.06MPa in the fixing test using the fixing apparatus, but was a constant for the contact area between metal plates and vulcanizates in the range of 0.05 from 8.

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