Experimental Study On The Deformation And Damage Of Composite Adhesively Bonded Joints And Bimetal Solder Film

The interlaminar deformation and damage of adhesively bonded joints in carbon fibre—reinforced plastics(CFRP), the fatigue failure mechanism of bimetal solder joints in an electranic package caused by thermal strains, are the problems provided by modern science of material and electronics, on which micromechanics are focuousing. In the paper, a general study and analysis has been performed on these problems using modern technique of laser and grating. In addition, the carrier technique in Moire' interferometry was theoretically generalised with fringe vector and wavefront interference. The interlaminar shear strains, the strain distributions along the adhesive line of joints in CFRP and the solder film of joint in Cu-Kovar with loads and temperature, was all been achieved and analysed succefully, also the failure mechanism of two kinds of joint was experimental studied. specifically, the followings was included.The mechanical behaviour of composite double-lapped adhesively joint subjected to compressing loads, such as shear strain distribution along the adhesive and its variation with loads, joint damage etc., have all been studied and analysed using carrier fringe technique in Moire' interferometry. The expermental results of joints coincide with the theoretical conclusions.Mechanical differentiation and double exposure for normal and shear strains of composite double-lap joint, was performed, the whole field fringes of shear strains was produced based on contour maps of derivatives of displacements. Thus only according to the fringes order would the shear strain distributions along the adhesive be determined, also the multipliation of Moire' fringes was proposed to promote the sensitivity of strain measurement.Interlaminar and adhesive strains was analysed experimentally for com-posite double—lap joint subjected to bending loads. Its distribution and variation with load was determined. In addition, Its damage was studied.The thermal strains created from a mismatch of coefficients of thermal expansion (CTE) between laps in composite joint, was studied experimentally. A method for canculation of thermal strain of composite was proposed for the using of Moire' interfermetry.Thermal strains in a thin continuous film of solder (62Sn-36Pb—2Ag), caused by the mismatch of coefficient of thermal expansion (CTE) between bimetal plate (Cu and Kovar), was analysed with Moire' interferometry. It is important for the realization of mechanism of fatigue failure of solder joint in an electronic package.Expermental study was performed on bimetal (Cu and Kovar) solder joint subjected to shear loads. The shear strains in thin film of solder was determined. The results show that moduli of bimetal plate has affectson the distribution of shear strain in the solder.