Mechanism of Adhesive in Secondary Bonding of Fiberglass Composites with Peel Ply Surface Preparation

Abstract

The surface composition and morphology of fiberglass/epoxy composites prepared by the use of “bondable” peel ply and sanding will be presented. “Bondable” peel ply is a material which provides a surface ready for secondary bonding following peel ply removal without requiring further treatment. The available results indicate mechanisms which may degrade bonds using “bondable” peel ply. Those same results also give insight into how “bondable” peel ply achieves a bondable surface when conditions are optimal. Optimal conditions can produce a surface whose 90° peel strength is 12–15 lbs/in-width versus suboptimal conditions which produce strengths of 1–4 lbs/in-width. The case studied in this effort is 350°F curing fiberglass/epoxy bonded secondarily with 250°F curing toughened epoxy adhesive.

Marine Composites Based on Low Styrene Content Resins. Influence of Lamination Procedure and Peel Plies on Interlaminar Resistance

“…The mechanism proposed by Kieronski et al [9], nylon fibre residue left on the surface after peel ply removal, appears to be a plausible explanation for the poor adhesion, but no fibre residues were detected here.…”

“…A second possibility is that proposed by Kieronski et al [9], that part of the peel ply fabric itself is left on the surface after peel ply removal. The properties of polyamide fibres are closely related to manufacturing conditions, but published studies have revealed the existence of a core/skin structure [17].…”

“…Recent results from tests on glass/epoxy composites indicated improved lap shear strength with polyamide peel plies compared to polyester, and showed the importance of surface morphology after peel ply removal [7,8]. Kieronski et al also examined the use of peel plies to protect glass reinforced epoxy composite surfaces [9]. They showed that while an optimal peel ply can leave a surface ready for secondary bonding without further treatment, if a "sub-optimal" peel ply is used its removal can leave a thin skin of polymer on the surface, which inhibits subsequent bonding.…”