Residual stress variation and deformation of shot peened glass fiber reinforced composites/aluminum–lithium laminates under thermal shock and thermal fatigue

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AbstractThis paper aims to reveal the deformation mechanism of glass fiber reinforced composites (GFRP)/aluminum–lithium (Al–Li) laminates under thermal shock or fatigue and verify reliability of shot peen forming for the composites. In this study, residual stresses in laminate after shot peening was analyzed using finite element model, and the simulation results were verified by experiments. It was found that the shot peened laminates, compared with pure metal panel, similarly exhibited compressive stress at the two external metal surfaces and tensile stress in GFRP layer. The residual stresses changed discontinuously at the metal/fiber and 0°/90° fiber interface owing to the different modulus. Moreover, stresses generated during curing process significantly affected the final deformation after shot peening. Residual stresses altered in each layer with the increase of temperature from 0 to 100°C, which caused the arc height of the laminate decreased. However, the arc height increased to initial dimensions when the temperature dropped to 0°C. Thermal shock process was proved that it hardly influenced the sample geometry. The stress relaxation behaviors were found in long‐term thermal fatigue. 1100 cycles from −55 to 100°C, which lasted 4 h in every cycle, resulted in 5% decrease of the arc height. The deformation problem should be further concentrated on for components made of GFRP/Al–Li laminates and processed by shot peen forming technology.