Evaluation of Mode II Interlaminar Fracture Toughness of Composite Laminates under Impact Loading

Rate-Dependent Mode Ii Interlaminar Fracture Behavior of Carbon-Fiber/Epoxy Composite Laminates

“…Especially, the mode II interlaminar fracture toughness has been regarded as important for selecting the materials of large-sized aircrafts, because it has been considered to be closely related to the CAI (Compression After Impact) performance [3]. Very few investigators [4][5][6][7][8][9][10][11][12], however, paid special attention to the mode II impact fracture toughness or the rate dependence of fracture toughness, though the matrix resin such as epoxy shows not a little rate dependence of fracture toughness [13,14]. This seems to be because the estimation of impact fracture toughness is difficult owing to the kinematic effects of the specimen and measuring system [15].…”

The effect of loading rate on the fracture toughness of fiber reinforced polymer composites

“…Kusaka et al20, 21 explored the strain rate effects of fracture toughness of unidirectional carbon/epoxy composites using a split Hopkinson pressure bar (SHPB) and found that the fracture toughness decreased by 20% over 8 decades of loading rate. The SEM observations indicated that the results were caused by fractographic differences: The specimen fracture surfaces were smooth at high strain rates as a result of debonding at the fiber matrix interface, and the matrix surface is only deformed a little; but the specimen fracture surfaces at low rates highlighted the presence of hackle markings due to ductile fracture in the matrix resin.…”

Dynamic Effects in Hopkinson Bar Four-Point Bend Fracture

“…In a 2-bar/single-edge notched tension Hopkinson bar fracture test, Owen et al [3] demonstrated that the quasi-static fracture mechanics theory could be used to calculate the stress intensity factor after stressstate equilibrium is attained. In a Hopkinson bar loaded mode II interlaminar fracture test, [32] Kusaka et al demonstrated by finite element analysis that the stress state and deformation mode for the specimen under stress wave loading is approximately equal to those under quasi-static loading when the incident stress wave of adequate amplitude and rise time is applied to the specimen. That is to say, the inertial effect on the specimenÕs dynamic behavior can be reduced by using a ramped incident stress wave.…”

“…Therefore, it is essential to achieve stress-state equilibrium in the cracked fracture specimen for a valid Hopkinson fracture test. However, only a few authors [3,22,23,26,32] have considered the effect of stress-state equilibrium in the Hopkinson bar loaded fracture test. Corran et al [22,23] have investigated the time required for stress equilibrium in 2-bar/wedge-loaded compact tension fracture test and demonstrated that quasi-static equilibrium across the nonuniform section of the loading bars is achieved after 60 to 70 ls.…”

“…The loading methods adopted for the Hopkinson compression pulse fracture test are numerous, including a single incident bar setup, referred to as 1-bar (only incident bar) impact; [4][5][6][7][8][9][10][11][12][13] 2-bar (including incident and transmission bars) setups; [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] and 3-bar (one incident bar and two transmission bars [each transmission bar as a support]/three-point bend) impact. [30][31][32] In such Hopkinson pressure bar loaded fracture tests, both the dynamic loads applied on the specimen and the specimenÕs displacement are determined by the one-dimensional stress wave theory, while the methods to determine load and displacement are different. In the one single incident bar setup, the load and load-point displacement can be determined by onepoint [5,8,9] and two-point strain measurement techniques.…”