Research On Stiffness And Strength Of Resin Matrix Composite Laminated Structures Under Hydrothermal Environment

Owing to the high strength and stiffness tolerance in carbon fiber reinforced polymer composites,they are widely used in aerospace, defense and other fields instead of the traditional aerospacematerials such as aluminum, steel, titanium etc. Their usage has become nature of the landmark foraerospace structural. Hydrothermal environment is one of environmental factors, which is frequentlyencountered by aircraft, especially due to absorption of moisture from the atmosphere in thehigh-speed flight and during the encounter of aircraft structure in the joint action of high temperature,and cyclic （fatigue） loading effects. It has been recognized that hydrothermal environment can causereduction of the strength of composite materials so it devotes a lot of human resource for further studyin the field, so as to reasonably and effectively using of composite materials.This article will address some issues related to effect of hydrothermal environmental conditionson carbon fiber composites. In order to adopt strength and stiffness and other mechanical properties ofthe laminate, an experimental program of unidirectional laminate T300/BMP-316is conducted usingmaterial for researching the static behavior of the unidirectional ply. Three different temperatures（22℃,80℃,120℃） and three moisture content （0,0.5%, saturation） of nine different conditionswere selected to imitate hydrothermal condition at first; secondly, the strength of the unidirectionallaminate with three different layers including [0]₁₆,[90]₁₆, and[±45]₄₅has tested in order to obtain thefour stiffness parameters and five strength parameters of carbon fiber composite material in differentconditions, the data which is obtained by test has a smaller dispersion, so the results are reliable.A progressive damage method of the finite element analysis in fibre-reinforced plastics underhydrothermal environment is established in the paper, which is based on the principle of virtual workand the theory of unidirectional ply. The three-dimensional Hashin-type failure criteria, the criteria ofthe structure catastrophe and the sudden material property degradation rules are introduced into thismethod. Based on the ANSYS, A progressive damage analysis coding for predicting the static strengthin fibre-reinforced plastics under hydrothermal environment is established.Finally, the ultimate strength of composite in static tension loading conditions is predicted byusing the static damage method established in the paper. The results show that, the static strengthprediction method can be used to predict the laminate strength.