A nondestructive method for evaluating natural frequency of glued-laminated beams reinforced with GRP

Experimental, theoretical and numerical investigations into dynamic properties of glued-laminated (glulam) beams reinforced with various lay ups of E-glass reinforced epoxy polymer composites (GRP) are discussed. The main objective was to demonstrate the applicability of the GrindoSonic instrument (GSI) as a part of a simple method for assessing the dynamic properties of such composites. For that, three unreinforced glulam (control) beams and eleven glulam beams reinforced with GRP on their bottom surface were instrumented. The beams were also tested using an instrumented hammer. The other objective of this investigation was to present a novel methodology for evaluating the natural frequency of the beams. Two types of shape functions were used for this purpose, namely: the exact transcendental function and the polynomial function. The finite element method (FEM) was also employed. As the last objective, we evaluated the influence of several parameters on the fundamental natural frequencies of the beams was also investigated. The natural frequencies of all beams determined by the theoretical methods and impact dynamic (hammer) method using the PSD were compared to the values obtained through the GSI. The comparison indicated that the proposed nondestructive method could be effectively used to establish the dynamic properties of glulam reinforced composite beams.