Impact Damage And Residual Compressive Strength For Composite Laminates Subjected To Low Velocity

The composite materials are widely used in the aerospace due to their high specificmechanical properties, such as high stiffness-to-weight, high strength-to-weight and soon. But the structure is susceptible to impact damage, especially the low energy impact,which will seriously weaken the bearing capacity of composite laminates. The lowvelocity impact will lead to the structure producing a certain degree of damage insidethe material, generally including matrix cracking, delamination and fiber breakage. Andvarious forms of damage will be interacted with each other, further aggravating thedamage of material. These internal damage can not be timely detected and repaired, soit has a great influence on the residual compressive strength of structure. This paper hasstudied impact damage of composite laminate under low velocity and the residualcompressive strength after low velocity impact by means of test and finite elementsimulation. The main research contents are as follows:(1) The low velocity impact tests were carried out with different impact energy onthe laminates of different layers. Through ultrasonic C scan, the damage characteristicwas obtained;(2) Conduct compression tests under normal temperature. Through compressiontests, the damage propagation, failure load and residual compressive strength ofdamaged laminates was obtained. It proved that the residual compressive strengthgreatly decreased as the laminates were impacted;(3) Based on PATRAN/NASTRAN software, establish the finite element model ofcomposite laminates subjected to low velocity impact and discuss the damage evolutionof the laminates.Then the whole process containing low velocity impact damage andcompressive analysis was achieved by setting the state after impact as initial state ofcompression simulation;(4) Select a part of impacted laminates to conduct moisture absorption test andcompression test under high temperature. The effects of hygrothermal environment onresidual compressive strength of composite laminates were discussed.