| Aluminum foam is a new type of engineering material,with low density,high specific strength,good shock absorption effect,high energy absorption,excellent sound insulation effect,high electromagnetic shielding efficiency and other excellent properties,have been widely used in automobiles,ships,satellites,spacecraft,military equipment,road sound insulation and other aspects.However,the low strength of aluminum foam makes it easy to deform and fail in harsh environments,which greatly limits its application in engineering.Studies at home and abroad have shown that interpenetrating phase composites can be obtained by filling the holes of aluminum foam with polymer,and its mechanical strength and impact resistance have been greatly improved,which has become one of the main methods for strengthening aluminum foam.In this paper,PU-PUR was blended to solve the defects of polyurethane(PU)with low strength and large deformation under stress and polyurea(PUR)with brittle fracture failure under stress.Then PU-PUR/Al Foam composites was prepared by filling the blend resin into the holes of open-cell aluminum foam.The properties of PU-PUR blend resin and PU-PUR/Al Foam composites were studied.The main contents are as follows:(1)The study on PU-PUR resin blend system:(1)The rheological properties of PU-PUR system were analyzed,and the optimal curing temperature and curing time of PU-PUR resin blend system are determined based on the comparison with DSC curve.(2)The tensile and compressive properties of PU-PUR blend resin casting body were tested,and the stress-strain curve,elastic modulus and strength,compressive specific energy absorption and tensile elongation at break were analyzed.The results show that:The compression failure strain of M4(PU/PUR=3:7)resin casting body is 0.51,the tensile elastic modulus and strength are960.67 MPa and 11.84 MPa,the compressive elastic modulus and strength are 248.43 MPa and 42.65 MPa,and the compressive specific absorption energy is 9862.33 m J/g.The tensile elongation at break is 25.82%,the comparative analysis shows that M4 resin casting body has the best toughness and strength under tensile and compressive loads.(3)The SEM view of the tensile section shows that the tensile section of the casting body is flat and no phase separation occurs,and the compatibility between PU and PUR is good.(2)The study on Al Foam and PU-PUR/Al Foam composites:(1)The drop hammer impact test was carried out,and the failure morphology,load-time curve,load-displacement curve and energy-time curve were analyzed.Al Foam has fast response speed and high energy absorption ratio during drop hammer impact,Al Foam is an excellent material under drop hammer impact.In PU-PUR/Al Foam composites,M4(PU/PUR=3:7)/Al Foam and M5(PU/PUR=0:10)/Al Foam have fast response under drop hammer impact.The peak load of8196 N and 8668 N and the peak energy of 48.518 J and 48.476 J can be reached within 1.92ms and 1.86 ms respectively.The impact duration is 7.53 ms and 7.37 ms,the total displacement is 6.93 mm and 6.25 mm,the energy absorption ratio both of them are 93.71%,it can be seen that the values of the above properties of those two composites are very close.However,the brittle fracture phenomenon of polyurea resin results in more cracks on the back side of M5/Al Foam and get wide extension range,which makes it more prone to brittle failure when subjected to impact load.The 30%PU in M4/Al Foam resin enhances the toughness of the resin,and the crack extension is blocked after impact,which enhances the impact resistance.The results show that M4/Al Foam is the best composite material to resist the drop hammer impact load.(2)The compression test was carried out,and the compression stress-strain curve,compression elastic modulus and strength,and compression specific energy absorption were analyzed.The existence of aluminum foam skeleton have solved the deformation and brittle failure of PU and PUR resin when the compressive strain is large,the strain of M1(PU/PUR=10:0)/Al Foam and M5/Al Foam composites is 0.27 and 0.08 higher than that of PU and PUR resin casting body,respectively.The compressive elastic modulus and strength of M5/Al Foam are 851.95 MPa and 107.32 MPa,and the compressive specific absorption energy is 26925.15 m J/g,which are higher than other composite types.The results show that M5/Al Foam is the best composite material to resisting compressive load.(3)The impact test of simply supported beam was carried out.The impact toughness of M4/Al Foam and M5/Al Foam are highest and close,which are 46.15 k J/m~2and 44.98 k J/m~2respectively.Both of them are the best composite materials to resist the impact load of simply supported beam. |
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