Fatigue Lifetime Prediction of Angle-Plied Fiber-Reinforced Elastomer Composites as Pneumatic Tire Materials

Abstract

An initiative is underway to realign the test procedure where the emphasis is placed on more cost-effective and less empirical laboratory predictions of fatigue life of aircraft tires. The initial goals are to define the deformation and fracture mechanisms of various critical regions of aircraft tires and to identify the parameters that control the process of fatigue damage accumulation for cord-reinforced elastomer composite elements. The first phase of our study is focused on the delamination of bias aircraft tire carcass in the shoulder area. The study examined the effect of a broad range of the combination between different loading parameters on the fatigue resistance of angle-plied elastomer composites. Among them, stress amplitude was found to play a dominant role in determining fatigue lifetime of composites. The damage accumulation process of composites was accompanied by a continuous increase of cyclic strain (i.e., dynamic creep), temperature and acoustic emission (AE). The dynamic creep rate and the rate of temperature increase were inversely proportional to the fatigue life according to a power law. When the minimum cyclic stress was high enough, distinctly different rates of AE signal accumulation could be assigned to the cord-matrix debonding and delamination failure modes. The results demonstrated a great potential of the measurement of local strain change, heat generation, and AE as a viable experimental technique for real-time monitoring of the damage accumulation process. Finite element analysis was used to approximate the stress and strain components in the composite coupon specimens. Two finite element models were created using 75 and 1500 elements, respectively. The 1500 element model was shown to produce much better results for the σz stress distribution, while both models produced similar results for the σx and σxz stress distributions. The predictions were in good agreement with the total axial load measured experimentally.