Crashworthiness Of CFRP Thin-walled Structures Considering Temperature And Humidity Effects

As a highly promising lightweight material,carbon fiber reinforced plastics(CFRP)composite are widely used in aerospace,marine and automotive industries,which could expose to low or high thermal environments with varying material properties.However,the service environment of CFRP Composite is very complex.Complex environmental factors will affect the mechanical properties of the CFRP structure to a certain extent.Therefore,it is urgent to carry out a series of basic scientific research to explore the residual mechanical properties of materials after aging.In order to analyze the mechanical properties of CFRP composites after aging,a series of high temperature aging and hydrothermal aging experiments were carried out.This study investigated the effects of temperature variation ranging from-30?to 160? on tensile properties of CFRP experimentally and theoretically.The specimens were prepared using thermo-forming technology;and the glass transition temperatures of epoxy resins were measured by dynamic mechanical analysis.Digital image correlation(DIC) technique was used to capture the variation in strain and damage fields.By means of scanning electron microscopy(SEM),the failure mechanisms,delamination and resin softening,were identified by scrutinizing the images of fracture areas subject to different temperatures.The two-parameter Weibull analysis was conducted to evaluate the theoretical tensile strengths from relatively discrete data.The obtained Weibull parameters are considered useful for the reliability analysis of CFRP structures.It is found the tensile strength decreases with the increase of temperature in a nonlinear fashion,which can be modeled by a tanh function by correlating with the temperature-dependent experimental data.The study is anticipated to provide a fundamental unde rstanding and predictive tool for mechanical strength of composite structures operating under different thermal conditions.The crashworthiness of thin-walled CFRP tubes immersed in 30? and 70?pure water for a long time at 30?160 ? was studied experimentally.And the glass transition temperatures of epoxy resins were measured by dynamic mechanical analysis.It is found that EA,sea and fmean of thin-walled CFRP tubes decrease obviously with the increase of temperature.Compared with room temperature,t he average crushing loads of thin-walled CFRP tubes at 70 ?,100 ? and 160 ? are65%,14% and 6% respectively,and the failure modes change significantly.The results show that temperature has an obvious effect on the moisture absorption characteristics of CFRP Composite.The water absorption of CFRP thin-walled tube immersed in 70 ? pure water for a long time is about 10 times of that at 30 ?.Long term immersion in room temperature purified water has no obvious effect on the crashworthiness of thin-walled CFRP tubes.The crashworthiness of CFRP thin-walled tubes immersed in 70 ? purified water for a long time decreases obviously,and the average load decreases by 25%.