Available at: http://digitalcommons.calpoly.edu/theses/1670
Date of Award
MS in Mechanical Engineering
Joseph D. Mello
As the use of fiber-reinforced composites has increased over the decades, so has the need to understand the complexity of their failure mechanisms as engineers seek to improve the damage tolerance of composite laminated structures. One of the most prevalent and limiting mode of failure within composite laminates is delamination, since it not only reduces a structures stiffness and strength, but can be very difficult to detect without the use of special non-destructive equipment. Industry testing organizations have utilized several fracture tests in order to characterize the fracture toughness of composite materials under different loading conditions. For this research, ASTM D5528, ASTM D7905 & 4ENF tests were performed to evaluate the fracture resistance of uni-directional pre-preg laminates; the 4ENF was used to compare its effectiveness as to ASTM D7905.
Finite element methods such as the use of cohesive elements have been developed to simulate delamination within composite laminates. While there has been much work in evaluating the effectiveness of cohesive elements, very little exists within literature as to studying the success of cohesive surface contact for accurately modeling coupon level fracture testing. Cohesive contact interaction in Abaqus/Standard was used to simulate the mode I double cantilever beam (DCB) experiment of ASTM D5528. Cohesive contact was found to accurately and efficiently model DCB testing as the critical load- displacement values and steady state fracture agreed with experimental data. A parametric study was performed and found that cohesive contact was less sensitive in varying key model parameters than that commonly expected of cohesive elements.