This work focuses on analyzing the uniaxial response of carbon fiber reinforced polymer matrix laminates with the configurations [±45]2S under tension and [±45]4S under compression. These present non-linear stress-strain evolutions that allow them to withstand large deformations before losing their load-carrying capacity. Both responses are characterized by a first linear stage, followed by a plateau in which the strain grows without increasing the stress level, and finally by a re-stiffening phase. But there are quantitative differences that lead to different failure patterns, which are explained with the help of the state of stress in the plane of maximum shear stress. For a better understanding of the process, tensile load-unload-reload tests are performed to verify if the energy recovered in each cycle could be related to the loss of the apparent stiffness. During the first two stages of the mechanical response, the laminate suffers a progressive damage with a reduction in stiffness related to the dissipated energy, but this pattern is not repeated in the last stage of strain hardening. Based on the experience of other authors, it is assumed that the re-stiffening stage follows a different pattern due to possible microstructural changes in the matrix during the plateau. These are promoted by a narrowing process under tensile loads and a local widening of the test zone under compression. The dimensional changes perpendicular to the load direction are observed thanks to the strain fields obtained by Digital Image Correlation.
Abstract
This work focuses on analyzing the uniaxial response of carbon fiber reinforced polymer matrix laminates with the configurations [±45]2S under tension and [±45]4S under compression. These present non-linear stress-strain evolutions that allow [...]
En este trabajo se presenta un estudio combinado experimental/numérico para evaluar la respuesta de un CFRP tipo tejido ante ondas de choque, representativas de cargas impulsivas debido a explosiones. Los ensayos experimentales se realizaron en el denominado ‘SIMLab Shock Tube Facility (SSTF)’, en la Universidad de ciencia y tecnología de Noruega (NTNU). Se ensayaron laminados a distintas presiones para investigar su comportamiento desde una respuesta elástica hasta el fallo total. Además, se emplearon dos cámaras de alta velocidad para obtener, con la metodología 3D-DIC, los campos de desplazamientos. Con el fin de estudiar el daño interno producido en los laminados se emplearon técnicas de inspección no destructiva por ultrasonidos.
Para reproducir el comportamiento de los laminados se empleó un modelo de daño continuo, el cual tiene en cuenta los daños intralaminares del material compuesto como rotura de fibras. Los daños interlaminares se modelaron mediante el empleo de superficies cohesivas.