Fracture mechanic behavior of a type of stitch-bonded biaxial carbon epoxy composite is presented. The influence of damage modes such as separation, tow splitting, multiple cracks, and fiber bridging on the energy release rate initiation and resistance of thin and thick laminates is investigated. The possible effects of manufacturing and in-service environmental conditions on energy release rate initiation and propagation have been presented. Details of loading speed, crack velocity, plasticity zone, curing and environmental conditions for smooth and nonsmooth crack growth have been discussed. The curing and in-service conditions have been found to influence the mode I fracture behavior of composite laminates. The results showed that different propagation curves should be included in the design guidelines for stitch-bonded composites.