Fiber Bragg-Grating Sensors for SHM and FEM of In-Service Bonded Multi-Material Pi-joints

摘要

Prediction of the performance and the failure initiation in in-service adhesively bonded multi-material Pi-joints is of special interest for determining the maximum load carrying capacity and structural integrity of resulting components for marine, automotive and aerospace applications. Currently fiber Bragg-grating (FBG) sensors are being increasingly used to monitor the bonded region in adhesive joints as they do not affect the intrinsic bonding properties. This paper presents experimental and numerical study on in-service multi-material Pi-joints using strategically embedded FBG sensors. In-house manufactured Pi-joints consisted of various combinations of Aluminum, Steel and Glass Fiber Reinforced Polymer (GFRP) as adherends and used FM-94K adhesive provided by Cytec as the structural adhesive. Apart from intact Pijoints, Pi-joints with the manufacturing defect were also manufactured. Initially, Finite Element Modeling (FEM) was used to predict the behavior of Pi-joints with similar and dissimilar adherends under varying load conditions. Afterwards, FBG sensors were strategically placed in the regions of interest to monitor the strains during the longitudinal and transversal static loading of Pi-joints. A novel method for external FBG embedding was proposed and validated using strain gages. Proposed method allows easy remove and reuse of the FBG sensor. Strains measurements acquired by FBG sensors were validated by strains measurements obtained using strain gages. Experimental data from the embedded FBGs is further used to develop experimentally validated simulations (EVS) which in turn can be used as a design tool for multimaterial Pi-joints. Preliminary results demonstrate potential of the developed technique to predict the strain behavior and evaluate the performance of bonded Pijoints with similar and dissimilar adherends.