Effect Of Temperatures On Interfacial Bonding Strength Of Carbon Fiber/epoxy Resin Composites

Fiber reinforced composites are often applied to the different temperature environments.Interfacial strength is the basis to the composites design. The investigations on the fiber/resin interface strength under various temperatures will provide the basic parameters for the composites design.Herein we used pull-out method to test the pullout load-displacement curves of carbon fiber/epoxy resin composite interface. The tests were conducted under the environment temperatures of 20℃, 50℃, 80℃, 110℃ and 140℃. The interface bonding strength and pullout damage mechanisms were revealed from the dynamic mechanical analysis(DMA) data of the epoxy resin, interface failure morphologies, and numerical simulation results. The influence of the temperature on the interface strength has also been presented.The main results of this investigation are as follows:(1) From the DMA test, the glass transition temperature(Tg) of the epoxy resin is 110℃. The mechanical behaviors of the epoxy resin decreased significantly when its temperature is greater than the Tg. It was also found that the mechanical behaviors of the epoxy resin would not change a lot at a specific temperature after the resin has been exposed at this temperature for 1 hour.(2) The temperature equilibrium time of the composite coupon under a specific temperature has been obtained from finite element analysis(FEA) for simulating the heat transfer process of a full-size carbon/epoxy composite coupon.(3) There are different pullout failure modes of the carbon fiber/epoxy composite under different temperatures. The failure mode is interface debonding at low temperature while the resin tensile damage at high temperature.(4) The maximum pullout load is influenced by the interface bonding strength and resin strength.The load decreases as the temperature increases.(5) Temperatures have effcets on interfacial strength. interfacial strength decreased with the increase of the temperature.(6) The interface debonding initially occurred at the carbon fiber/epoxy resin interface and then the debonding gradually propagated along the carbon fiber direction. Finally the carbon fiber/epoxy resin interface failed completely and the carbon fiber tows were pulled out. The stress in the composite will be re-distributed.