Effect of service temperature and hygrothermal aging coupling on mechanical properties of adhesively bonded BFRP-Aluminum alloy joints

Abstract

To study the coupled effect of hygrothermal aging and service temperature on the mechanical properties of adhesively bonded basalt FRP-aluminum alloy joints (BFRP-Al joints), the mechanical properties and failure mechanism of BFRP-Al joints at different temperatures before and after aging were analyzed in this paper. The accelerated aging test of the adhesively bonded joint was performed under the hygrothermal condition (80 °C&95% relative humidity), and the hygroscopic property of the joint were analyzed by the water absorption test. Then, the mechanical properties of the aged joints were measured at 80 °C, room temperature (RT 25 °C), and −40 °C. The failure mechanism of the joints under the coupling effect of hygrothermal aging and service temperature was analyzed based on the Differential Scanning Calorimetry (DSC) results. The results reveal that the BFRP-AL joint reaches moisture saturation after exposure to hygrothermal environment for 200 h, and the moisture absorption behavior complies with Fick's law. Due to the decrease of material Tg caused by hygrothermal aging, the mechanical properties of the joint at 80℃ decrease more obviously after aging. Moreover, the failure modes of joint are altered as a result of hygrothermal aging and temperature coupling. A methodology for predicting the performance of bonded joints was established based on the variation laws in Tg and failure load, taking into consideration the effects of hygrothermal aging and service temperature which can provide guidance for the lifetime design of the hygrothermal aged adhesive structures within the entire service temperature range.