High Strain-rate Compression Behaviors Of Carbon/Epoxy Plain Woven Laminated Composites At High/Low Temperatures

Compared with unidirectional composites, plain woven laminated composites which have interlaced fiber tows along weft and warp directions, have better structure stability and impact resistance. The plain woven laminates have been more and more widely applied to dynamic resistant structures, such as aerospace, military industry equipment, automobile and ship. With the expansion of its application field, the plain woven composites will be definitely under impact loadings in high and low temperature environments. To characterize the compression behaviors of the plain woven composite would have significant effect on the structure design.In this paper, high strain-rate compression behaviors of carbon/epoxy plain woven laminated composites at high and low temperatures were investigated. Carbon/epoxy plain woven laminated composites were tested on the Split Hopkinson pressure bar (SHPB) with temperature control device under high strain rate (700～900/s,950～1100/s,1150～1300/s) and different temperatures (-80℃,-50℃,-20℃,20℃,50℃,80℃,100℃). The typical damage morphologies were observed through scanning electron microscope (SEM). The dynamic mechanical analyses (DMA) tests of epoxy resin were also conducted to study its thermodynamic properties. The effects of temperature and strain rate on the impact compression behaviors of plain woven laminated composites were analyzed. The experimental methods and the main conclusions of this investigation are as follows:(1) Instant test under different temperature conditions adopted temperature pretreatment method, ensured that the split Hopkinson pressure bar did not withstand temperature processing, avoided the influences of temperature on signal acquisition. For the sake of the experimental temperature accuracy, the related sample was used for predicting the real sample internal temperature, sample surface temperature was measured through thermocouple.(2) The DMA results of the epoxy resin showed that the storage modulus, loss modulus and loss tangent of epoxy resin decreased with the increasing temperature in the range of-80℃ to 20℃. In the rang of 20℃ to 100℃, loss tangent and loss modulus increased with the increasing temperature, the storage modulus decreased with the increasing temperature.(3) It was found that the temperature have a significant influence on compression behaviors. At the high temperature, the compression modulus and peak stress of the composites decreased with the increase of test temperatures. Under low temperature, the experimental stress vs. strain curves showed that peak stress and compression modulus of the composites increased with the decrease of test temperature.(4) The out-of-plane impact compression behaviors of carbon/epoxy plain woven laminated composites were sensitive to the strain rate. The compression modulus and the failure stress of the composites increased with the increase of strain rate.(5) Shear failure was the main failure mode of the carbon/epoxy plain woven laminated composites at high strain rates. The damaged extents increased with the increase of temperatures in the rang of 20℃ to 100℃, but decreased with the decrease of temperatures in the range of-80℃ to 20℃. Through scanning electronic microscopy (SEM) observations, we found the change of fiber-matrix interface. There are abundant fibers pulled out from the warp and weft yarns under the high temperatures. This makes the fracture of fiber tows with the irregular fractograph under the high temperatures. However, most of fibers are bonded together and have regular fractograph under low temperatures.