Study On Dynamic Mechanical Properties Of Carbon Fiber Reinforced Composite Materials Under High Strain Rate

As a new type of light weight structure material,carbon fiber reinforced composites polymer(CFRP)have been widely used in aerospace and bulletproof fields.The mechanical properties,damage performance and failure mechanism of CFRP under high strain rate are the fundaments for high-speed impact mechanics analysis.However,current research on high speed impact mainly focus on metal materials,the dynamic response of composite materials under high strain rates and the corresponding failure mechanism is a great challenge,and become the hot spots of current research in various engineering applications.In this thesis,a combination of theoretical analysis,experimental investigation and numerical simulation are used to study the dynamic response,constitutive model and damage characteristics of composite materials.It will provide valuable theoretical basis and key technology for further revealing the failure mechanism and failure mode of composite materials under high strain rate.This article studied the dynamic mechanical properties of CFRP laminated plates under high strain rate by using high-speed tensile testing machine and Hopkinson bar testing device.Considering the shape scale of specimen and the form of clamp connection,the experiment protocol for dynamic tensile,compression and shear tests of composite materials was evaluated and re-designed in order to obtain more ideal dynamic test data.According to the newly proposed testing protocol,the performance of dynamic mechanical behavior test platform of CFRP under high strain rate was validated,and the dynamic tensile,compression and shear tests under different strain rates were carried out.Experiment characterizations indicate that CFRP under high strain rate have significant strain rate hardening effect,and the strain rate sensitivity of the in-plane shear properties of CFRP is higher than the interlaminar shear performance.Based on test results,in which the modulus and strength of CFRP are linearly related to the logarithm of the strain rate,a 3D dynamic constitutive model of strain-rate-dependent composite materials is developed by introducing a dynamic enhancement factor.Meanwhile,by modifying the 3D Hashin criterion and introducing a damage parameter,a 3D dynamic continuum damage constitutive model of composite material under multi-mode failure criterion was developed.Commercial finite element analysis package(ABAQUS)is applied with user defined subroutine(VUMAT)to develop the high-speed impact numerical simulation model of CFRP.Compared to the test results,the accuracy of the dynamic constitutive model of composite material is validated.This thesis adopts the dynamic test scheme and rate-related constitutive model of CFRP,which can be used to study the dynamic test and dynamic mechanical properties of composite materials and accurately predict their mechanical behavior under high strain rate.This research has important theoretical value and practical significance because it can provide the key technology for the high-speed impact structure design of composite materials meeting the engineering requirements.