2 research outputs found
Study of Biaxial Fatigue Behavior of Fiber Reinforced Polymers Under Tensile and Shear Loadings
Fiber reinforced polymers are used in many structural applications in the
aerospace and automotive industries because of their high strength to weight and high
modulus to weight ratios. In many of these applications, they are used as thin laminated
panels comprising of multiple layers of continuous fibers embedded in a polymer matrix.
In general, these laminates behave as an orthotropic material and their properties are
direction-dependent. While their uniaxial static and fatigue characteristics have been
studied extensively, their biaxial static and fatigue characteristics are not well established.
One reason for this is the difficulty of conducting biaxial tests, especially under cyclic
loading conditions. The objectives of the current research are two folds: (1) develop a
biaxial test method that can be applied to a range of normal and shear loadings, and (2)
study the biaxial fatigue behavior of a fiber reinforced polymer laminate using the new
test method.
The test method developed in this research is based on a butterfly-shaped Arcan
specimen. The versatility of the Arcan specimen is that it can be utilized for testing
materials under uniaxial normal loading, shear loading or a combination of in-plane
normal and shear loadings. The laminate considered in this study was a [0/90/04/0]S Eglass/epoxy.
Finite element analysis of a butterfly-shaped Arcan specimen was conducted first to establish its optimum geometry and delineate the importance of the
stiffness of the test fixture on the stresses in the significant section of the specimen. An
Arcan loading fixture was designed with the capability of loading of flat laminate
specimens under various combinations of in-plane tensile and shear stresses. Quasi-static
and fatigue tests were conducted with four different specimen configurations containing
either 0, 30, 45 or 90o
fiber orientations in the outer layers. The quasi-static strength
followed a quadratic failure envelope on a normal stress-shear stress plane. Biaxial
fatigue tests were conducted under combined tensile and shear stresses to determine the
effect of biaxiality on the fatigue performance of the laminate. Development of fatigue
damage under biaxial loading was also studied. A new fatigue life prediction model was
proposed that can be used to account for the effect of biaxiality on the fatigue life of fiber
reinforced polymer laminates.Ph.D.Automotive Systems Engineering, College of Engineering and Computer ScienceUniversity of Michigan-Dearbornhttp://deepblue.lib.umich.edu/bitstream/2027.42/136076/1/Mandapati Final Approved Dissertation.pdfDescription of Mandapati Final Approved Dissertation.pdf : Dissertatio