Investigating the effect of thermal cycles on the recovery of tensile strength in self-healing composites under impact loading

Here the healing process of glass/epoxy composites is studied experimentally. The healing agent is composed of ML506 epoxy resin and HA-11 hardner which is charged into microtubes. The microtubes are interleaved between the first and the second and the fifth and the sixth layers. The initial damage is introduced to the samples by drop weight impact tests and the recovery percentage of the tensile strength due to healing process is measured by tensile test. The effects of healing time (without thermal cycles), number of healing units and thermal cycles are investigated on the recovery of the tensile strength. Composite samples containing 8, 16 and 32 healing units are studied in the periods of 1, 6 and 12 days after the initial damage. Also, some damaged samples are set to 1, 3, 5 and 7 thermal cycles and after one day, tensile tests are carried out. The results show that without thermal cycles the healing process is almost completed after 6 days with an 83% recovery. In addition, the maximum amount of tensile strength recovery is equal to 86% which is related to the samples with 32 healing units after 12 days. This amount of healing efficiency can also be achieved by means of 5 thermal cycles. This is also true for thermal cycles where the effect of thermal cycles is tangible up to 5 cycles.