Cailiao gongcheng (Dec 2022)
Low velocity impact response and post impact compression behavior of BMI matrix composites
Abstract
A novel kind of lattice-distributed ESTM-fabrics was developed by using polyethersulfone(PES) and U3160.The loading amounts of PES on ESTM-fabrics are 15 g/cm2(ES-15), 25 g/cm2(ES-25), 35 g/cm2(ES-35), respectively. ESTM-fabrics reinforced BMI resin (trademarks: 6421) matrix composites(ESTM-fabric/6421) were prepared through RTM process.Dynamic mechanical thermal analyses(DMTA) and impact resistance as well as residual strength of ESTM-fabric/6421 were studied and the toughened mechanism was analyzed by fluorescence microscope.An untoughened 6421 BMI resin matrix composite (ES-0) reinforced by neat U3160 fabrics was studied to compare performance of composites as well.The results of DMTA show that ES-0 has only one glass transition temperature(Tg) representing pure BMI resin.The toughened composites exhibit two Tg: the relaxation peak appearing at 230-250 ℃ represents toughener PES phase and the relaxation peak appearing at 191-195 ℃ represents BMI phase. The results of low velocity impact testing show that the initial damage threshold load(DTL) is decreased significantly. DTL of toughened composites is far greater than ES-0 sample, which is the same as maximum peak load.With the increase of PES loading in toughened composites, DTL are increased and the projected delaminated areas are decreased.Fluorescence microscopic results of the specimens after low velocity impact show that the major impact failure of ES-0 sample is delamination. The toughened composites exhibit a great deal of interlaminar and intralaminar matrix crack under the impactor as well as more serious ply splitting on the back surface of specimens, which conical damage is less than ES-0 sample.The compression strength after impact(CAI) of ES-0 sample was 144.66 MPa while CAIs of the toughened composites ES-15, ES-25 and ES-35 increased to 205.85 MPa, 265.74 MPa along with 275.14 MPa, respectively. Fluorescence microscopic results of the CAI specimens reveal that ES-0 sample has massive delamination damage without ply splitting. A lot of ply splitting and obvious matrix cracks appear in ES-15 sample.The major impact failure of ES-25 and ES-35 samples is ply shear damage.These damage modes can absorb massive energy that lead to the higher CAI of the toughened composites.
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