Failure Behavior Of Composite Laminates With Low-velocity Impact Damage

With superior strength, specific module and designability, woven compositelaminate has been widely used in the aviation and space industries. Woven compositelaminate is sensitive to low-velocity impact, and low-velocity impact tends to causecracking or delamination of the matrix with no surface damage trace. These internaldamages may result in serious consequences. Therefore, it is significant to investigatethe failure behaviors and modes during the course of the low-velocity impacting as wellas the influence of impact damage on the performance of woven composite laminateplates.In the present work, the following studies were carried on CF3052/5224wovencomposite laminate plates. First, four damage grades were determined by low-velocityimpact testing under different impact energy, and then the failure modes and failurebehaviors after impacting under four different energies were studied by analyzing the pitdepth and crack length as well as using nondestructive examination and examination. Inaddition, the finite element analysis software, ABAQUS, was used to simulate theimpacting course of the laminate plates. At last, compression or bending tests werecarried out on the composite laminate plates with four different grades of damage afterimpact to investigate the effect of different grades of impact damage on the failuremodes during compression or bending. The results are summarized as follows.When the impacting energy is close to5.00J·mm-1, fiber breakage resulted in theobvious inflexion of pit depth. Before the inflexion, the internal damage of the laminateplates is mainly cracking or delamination of the matrix. After the inflexion, the internalfibers of the laminate plates rupture, resulting in the serious cracking of the matrix.The internal damage characteristics of the laminate plates were simulated byABAQUS finite element analysis. The simulation result is consistent with the testingresult. So it can be assumed that the failure behavior during low-speed impact testingcan be analyzed by ABAQUS.The CF3052/5224laminate plates with four different grades of impact damagehave the same compression failure mode—shear delamination failure, but they havedifferent local failure characteristics. The compression failure mode of the impact-damaged areas is flexion failure; other areas have the same failure as the plateswithout experiencing impact. In addition, the flexion failure area of the laminate platesafter compression increases with the rise of the impact energy.After flexion failure, the delamination of the impact-damaged areas is moreobvious than that of other areas. The failure mode of the whole plates is pure bendingfailure. With the rise of impact energy, the delamination of the impact-damaged areasbecomes more obvious, while the delamination area increases. Under the impact energyof1J·mm-1, there exist obvious shear delamination cracks in the undamaged areas.Under other impact energy, the side faces near the facture surfaces of the laminate platesafter bending have the same failure characteristics.