Low velocity impact response and post impact compression behaviour of ES^TM-fabric/3266 composites

Abstract

A novel kind of lattice-distributed ESTM-fabrics (ES-L) and random-distributed ESTM-fabrics (ES-R) were developed by using polyethersulfone (PES) and U3160 according to ex-situ toughening technology. ESTM-fabrics reinforced 3266 moderate temperature curing epoxy resin composites (ESTM-fabric/3266) were prepared through RTM process. Impact resistance and residual strength of ESTM-fabric/3266 were studied and the ex-situ toughening mechanism was analyzed by fluorescence microscope and SEM. The untoughened U3160 fabrics reinforced 3266 moderate temperature curing epoxy resin composites were studied to compare performance of composites as well. The result of low velocity impact testing shows that the toughened ESTM-fabric/3266 composites exhibit the higher delamination damage threshold load, the lower projected delaminated areas, the slower damage development, compared to U3160/3266 composites without toughener PES (ES-U).The major failure mode is intralaminar crack (transverse matrix cracking), debonding between fibre and matrix in fiber-bundle regions as well as local ply breakage along with ply-matrix debonding.The ES-L allows an increase of 37% in CAI compared to ES-U. Microstructural observation of damage zone reveals that ES-R composite has a homogeneous distribution of phase inversion in the interlaminar regions while ES-L composite exhibits a hard phase composing of the 3266 epoxy resin continuous matrix and a soft phase composing of the nodular structure of BMI in the 3266 epoxy resin continuous matrix. The excellent impact resistance and damage tolerance of ES-L composite are due to synergistic effects of hard phase and soft phase, which can release the stress concentration,give the extra strain energy dissipated and subsequently terminate crack via crack blunting mechanism.

Keywords

• toughening technology
• impact behaviour
• damage tolerance
• damage mode
• resin transfer molding (rtm)