Structural Adhesive Joints for Application to a Composite Space Frame - Analysis and Testing 880892

This paper presents an efficient adhesively bonded joint design for application to a composite space frame. After preliminary investigations were conducted to evaluate several alternative joint configurations, an adhesively bonded insert type T-joint was chosen for use in a composite space frame because of its high specific stiffness and large bond area. The stiffnesses of each joint were investigated both analytically and experimentally. Since the lower rail is the primary load bearing member, the joints along it were selected for a detailed study. Two types of analyses were completed. First, a formulation based on the layered beam concept and strain energy theorems was used as an approximate measure to evaluate the effects of varying geometrical parameters. The relationships between joint flange width, insert thickness, and weight were considered. Using the geometry determined by the approximate formulation, a finite element analysis was completed. The finite element model itself consisted of approximately 2800 solid isoparametric elements. All of the materials were modeled including the adhesive layer. The details of the two analysis techniques are presented in this paper.

Bending tests were used to verify the joint stiffnesses obtained. Three specimens were tested for each of the three joints considered under both fore-aft and vertical loading. The displacements were measured at the free end of the cross member where the load was applied.