损伤对层合复合材料分层的影响

基于损伤内变量理论,用准三维有限单元法,分析了分层尖端区存在损伤时,Ｊ积分、能量释放率Ｇ以及裂尖附近应力场的变化规律·结果表明,裂尖损伤区的存在对Ⅰ型分层扩展起到屏蔽作用,其屏蔽机理是:损伤的存在消除了裂尖附近应力的奇异性,并在裂尖周围形成一个低层间应力区；损伤导致裂尖附近Ｊ积分不再守恒,但能量释放率降低·

Effects of Damage on Delaminatoin of Laminated Composite

Based on internal damage variable theory, energy release rate and crack tip stress fields in the laminated composite with a though width symmetrical delamination were analyzed by means of quasi 3D FEM and the results were compared with those without the damage. Two kinds of damage models were used: interlaminar tension damage and shear damage. The numerical results indicate that the singularity of stress at crack tip disappears due to effect of damage. There is a lower interlamiar stress region around the delamination tip, and outside this zone the interlamiar stress increases. This is the reason of the shielding effect made by the micro crack damage. At initial stage of the damage J integral is path independent and equals to the energy release rate. J integral becomes path dependent and increases with damage evolution,and the energy release rate decreases,so that J integral cannot be used as the criterion of crack growing.