Composite materials have been increasingly used in both researches and industries, given their wide range of innovative applications and configurations. High-performance hybrid fabric-reinforced plastics stand out in this sector. In the present research, an epoxy-based vinyl ester resin laminate reinforced with bidirectional hybrid fabric consisting of carbon and Kevlar fibers is developed. In order to determine its mechanical properties and damage mechanism considering the anisotropy and the presence of geometric discontinuity (circular hole), this research focused on both experimental and analytical aspect. Concerning to geometric discontinuity, in the vicinity of the hole (known as a stress concentration area), characteristic distances ao and do associated to ASC (Average Stress Criterion) and PSC (Point Stress Criterion) failure theories, respectively, were determined. All the study of the composite material mechanical behavior was conducted based on uniaxial tensile tests. Their results show higher losses in the mechanical properties of the hybrid laminate, with respect to the anisotropy and the presence of the central hole, mainly when the orientation of the Kevlar fibers coincides with the direction of the applied load.

RESUMO Uma mulher de 21 anos desenvolveu uma massa mamária de grandes dimensões (17 cm). Exame físico e ultrassonografia revelaram um nódulo bem delineado, homogêneo e móvel, com características sugestivas de fibroadenoma gigante ou tumor phyllodes. O nódulo foi excisado e inicialmente interpretado como tumor phyllodes benigno. Subsequente revisão de lâminas estabeleceu o diagnóstico de hiperplasia estromal pseudoangiomatosa nodular associada a áreas de padrão fibroadenomatoide e focos de degeneração mixoide do estroma. Este caso ilustra a dificuldade encontrada no diagnóstico dessa entidade. Segue uma discussão detalhada do diagnóstico diferencial de hiperplasia estromal pseudoangiomatosa nodular.

ABSTRACT A 21-year old woman presented with a 17-cm left breast mass. Physical examination and ultrasound revealed the mass to be well-circumscribed, homogeneous and freely mobile, suggestive of giant fibroadenoma or phyllodes tumor. The mass was surgically excised and initially interpreted as benign phyllodes tumor. Subsequent slide review established the diagnosis of nodular pseudoangiomatous stromal hyperplasia (PASH) associated with fibroadenomatoid areas and myxoid stromal changes. This case illustrates the difficulty encountered in recognizing nodular PASH. A thorough discussion of the histopathologic differential diagnosis of nodular PASH is provided.