دانلود رایگان مقاله اثر آسیب در حالت شکست مفاصل کامپوزیت چند پیچ با روش شکست انولوپ

Abstract

Failure envelope method is comprehensively used in failure mode prediction of multi-bolt composite joints. The method is based on the assumption that bolt load distribution proportion is constant till failure. However, bearing damage and net-section damage must have some influence on the load distribution and then change structure failure mode. In this paper, tensile experiments of two-bolt and three-bolt joints were conducted to obtain the failure modes and other properties. Three dimensional (3D) finite element models involving damage were constructed, and the results were consistent with experimental data. Then, the models were used to study the effect of damage on failure mode of multi-bolt composite joints. The results show that failure mode prediction with failure envelope method should involve the effect of composite damage. Compared with net-section damage, bearing damage has greater influence on failure mode. Based on conventional failure envelope method, a new evaluation procedure involving damage was proposed.

6. Conclusions

In this paper the effect of damage on failure mode of multi-bolt composite joint using failure envelope method was studied. Experiments of two-bolt and three-bolt composite joints were conducted, and 3D finite element models containing composite damage were constructed. Bolt load distribution, bearing stress and bypass stress were calculated. Failure mode of the composite joints was predicted, and the effect of bearing damage and netsection damage were analyzed. These conclusions can be obtained: (1) Bearing damage and net-section damage can relieve the critical hole stress and change bolt load distribution with slope variation of the bearing vs. bypass stress curve. Therefore, composite damage must be considered in failure envelope method. (2) The failure mode of multi-bolt composite joints may change from bearing failure to net-section failure when damage is considered. The effect of bearing damage is greater than that of net-section damage. (3) OF (real stress curve) is limited between OM (curve neglecting damage) and line ON (curve supposing load uniformly distributed among bolts). When OM and ON intersect with the same line in failure envelope, structural failure mode can be determined with them. But structural failure mode is uncertain when OM and ON intersect with different lines, and further analysis is required.