Experimental Study On The Interfacial Residual Stress Of Resin Matrix Composites

Resin matrix composite is a fiber reinforced material based on organic polymers.It is widely used in aviation,automobile and marine industries.The properties of matrix resin and filler are the key factors determining the performance of resin based composites.However,the thermal expansion coefficient of the matrix and the filler is different in the process of the preparation of the resin matrix composites,and the shrinkage deformation will occur in the curing of the resin,which leads to the residual stress in the filler/matrix interface.Epoxy resin is a common matrix of resin based composite material,which can be encapsulated with its coated electrode and self-healing microcapsules to form a microcapsule/epoxy resin composite with self repair function.The residual stress at the interface between metal/epoxy resin and microcapsule/epoxy resin will seriously affect the mechanical behavior during service.Therefore,it is of great significance to test the distribution rule,size and influencing factors of interfacial residual stress.In this paper,the interfacial residual stresses of epoxy resin composites are studied from the following aspects:1.The temperature change of curing epoxy resin cured was monitored at room temperature.The results showed that the curing temperature of epoxy resin cured at room temperature changed little.The local curing and shrinkage deformation of pure epoxy resin was monitored by digital image correlation method.The result showed that the deformation rate of epoxy resin was corresponding to the temperature change.When the heating rate was large,the expansion strain value was large and the cooling rate was large,the shrinkage strain value was large.2.The microcapsule/epoxy resin composite also monitored the local curing and shrinkage deformation,and obtained the change trend of the microcapsule diameter in the whole process of epoxy resin,and compared with the local shrinkage deformation of the pure epoxy resin.The effect of local deformation of epoxy resin on the size of microcapsules were obtained.After curing with epoxy resin,the microcapsule was pressed and the diameter decreases.Moreover,the larger the microcapsule diameter,the more obvious the strain concentration existed.3.The metal cylinder with different elastic modulus and size was mixed with the epoxy resin matrix and the photoelastic stripe was measured by the microphotoelastic method.The value of the radial residual stress in the boundary surface was calculated by the plane photoelastic stress law and the principle of light compensation.The results showed that for different materials,with the same radius of the cylinder,as the elastic modulus of the cylinder increases,the residual stress increases.For the same material,the residual stress of cylinders of different sizes decreases with the increase of cylinder size.This was due to the size effect,the smaller the same material size,the greater the elastic modulus.4.Finally,in order to further verify the main influencing factors of the residual stress of the interface,this article also used polyether melamine microcapsules with an average diameter of 180 ?m to fill the epoxy resin to obtain the microcapsule/epoxy resin composite material,and the residual stresses at different microcapsule/epoxy interfaces were calculated by the spherical stress optical equation.The results showed that whether the filler was a cylinder or a microcapsule,the cross equal inclination line indicated that the interface was uniformly distributed residual compressive stress.Different from the cylindrical inclusion,the larger the size of the microcapsules,the greater the residual stress,which was due to the larger the size of the microcapsules,the greater their elastic modulus.