COMPRESSION AFTER IMPACT TEST METHOD FOR THIN LAMINATES

Compression After Impact (CAI) test has a strong interest in the aviation and aerospace industry, because a low velocity impact can cause a relevant decrease in the compression strength of composite structures. Besides, delaminations are particularly dangerous because of their difficult detectability. Furthermore, the structural components of many aviation and aerospace applications have thin thickness, of about 2mm. Unfortunately, the CAI standard prevents from testing laminates with less than 4mm of thickness, because buckling appears in the specimen. In a previous work, the authors developed a CAI device to test thin laminates. In this work the thickness range of laminates that can be tested at compression after impact was analysed, ensuring that the stress state is uniaxial and buckling not appear. Undamaged and damaged laminates of different thicknesses were tested, using two different devices: the ASTM D7137 device and the developed device. Furthermore, the problem was modelled to determine the buckling stress for different configurations. When the residual strength is higher than the buckling stress, the laminate should not be tested with that device. The simulations of composite laminates with and without damage show that the developed device can be used to test thinner laminates.