Research On The Effect Of Hygrothermal Aging On The Mechanic Property Of CFRP-Al Adhesively Bonded Joints

The traditional mechanical connection methods(bolting,riveting,etc.)to solve the problem of heterogeneous material connection in the automotive industry will destroy the connected material.And the bonding technology can ensure the integrity of the connected material,so it is widely used in the automotive industry.Automotives are often in an unfavorable aging environment during service,such as high temperature,high humidity,humid-heat cycling,salt spray,etc.The hygrothermal aging environment is more common,and it has a significant degradation effect on the mechanical properties of the bonded structure.Therefore,it is necessary to conduct an in-depth study on the mechanical performance of the bonding technology in hygrothermal environment.This article mainly studies the effect of hygrothermal aging environment on quasi-static tensile strength of the Araldite~?2015 dumbbell-shaped adhesive specimens and single lap joints composed of composite materials and metal.The main research contents are as follows:(1)First,the method of making a standard dumbbell-shaped adhesive specimen was introduced,and then the manufactured standard dumbbell-shaped adhesive specimen was subjected to a 14-day hygrothermal aging environment.Gravimetric method was used to obtain the quality change of the adhesive specimen at different moisture absorption time.The moisture absorption percentage-time curve of Araldite~?2015 dumbbell-shaped adhesive specimen was fitted to obtain the water absorption characteristic parameters of the adhesive.Afterwards,a quasi-static tensile test was carried out on dumbbell-shaped adhesive specimen that experienced different moisture absorption times,and the failure strength of the adhesives dependent on the moisture absorption concentration was obtained.(2)The method of making a single lap joint composed of CFRP and 6061A lightweight aluminum alloy is introduced in detail.The failure strength of three different kinds of single lap joints which vary in substrate is analyzed,and CFRP-aluminum single lap joints are used as the object to be aged.The effects of hygrothermal aging environment on the mechanical properties and failure modes of heterogeneous single lap joints are discussed.(3)The water absorption process of the adhesive layer was modeled and simulated,and the moisture concentration distribution in different regions of the lap joint adhesive layer was obtained.By introducing an aging factor related to the water absorption concentration of the adhesive layer,the key cohesive parameters of the adhesive layer in different areas of the lap joint are degraded.The quasi-static tensile process model of CFRP-aluminum single lap joints that undergo different aging times is established in the commercial software ABAQUS.The tensile failure process was analyzed and compared with the experiment result.Studies have shown that the failure strength of adhesives and adhesive joints that subjected to hygrothermal aging environment decreased with the increase of aging time.At the beginning of aging,the failure strength of joints decreases rapidly,and with the increase of aging time,the failure strength decreases slowly.The failure modes of adhesive joints are mainly cohesive failure and adhesive failure.The established finite element model predicts the failure load and failure process of lap joints successfully.