In　fiber-reinforced　composites,　the　interfacial　bonding　between　fibers　and　the　matrix　is　crucial　for　determining　the　material＇s　performance.　A　vacuum-assisted　resin　transfer　molding　(VARTM)　process　was　utilized　in　this　work　to　fabricate　glass　fiber　fabric-reinforced　polyamide　6　(GFF/PA6)　composites　through　in-situ　polymerization　using　caprolactam　(CL)　as　the　precursor.　To　enhance　the　fiber-matrix　interfacial　bonding,　polyethylene　glycol　(PEG)　was　incorporated　into　the　polymerization　system,　improving　the　hydrogen　bonding　between　the　matrix　and　fibers.　Morphological　observations　and　interface　layer　analysis　revealed　that　the　introduction　of　PEG　resulted　in　improved　interfacial　bonding　and　increased　interface　layer　thickness.　Molecular　dynamics　simulations　indicated　that　the　amino　formate　groups　formed　by　the　reaction　with　PEG　exhibited　more　hydrogen　bonds　with　the　hydroxyl　groups　on　the　glass　fiber　surface,　thereby　promoting　interfacial　bonding　between　the　matrix　and　fibers.　When　the　PEG　content　was　10　wt%,　the　tensile　strength　and　the　elongation　at　break　of　the　corresponding　composite　increased　by　160%　and　300%　compared　to　GFF/PA6　composites　without　PEG.　This　study　presents　a　promising　strategy　for　enhancing　the　fiber-matrix　interfacial　bonding　by　modifying　the　matrix,　offering　a　prospective　approach　for　developing　high-strength　thermoplastic　composites.　Highlights:　GFF/PA6　composites　were　fabricated　via　the　VARTM　method.　The　addition　of　PEG　for　matrix　modification　improved　the　interfacial　bonding.　The　modification　enhances　the　hydrogen　bonding　between　the　matrix　and　fibers.　Good　interfacial　bonding　can　greatly　promote　the　crystallization　of　the　matrix.　The　composites　exhibited　a　significant　increase　in　strength　and　toughness.　©　2024　Society　of　Plastics　Engineers.