Soil burial tests: Effect of soil burial exposure on the properties of structural grade reinforced plastic laminates

This paper is a summary of the effects of long-term soil burial on the properties of reinforced plastic laminates. The interactions of reinforcement, resin, and fabrication technique, as they relate to the laminates' ability to resist the effects of soil burial, are discussed. The method of soil burial attack is explained. Recommendations for the best laminate construction and methods of protection from the soil environment are made. These include: (i) Where there is a need for a laminate structure with the maximum initial mechanical properties and the largest percent retention of these values, a fully cured laminate with fiberglass cloth reinforcement and an epoxy resin matrix is recommended. (ii) Laminates made with an epoxy resin matrix or a polyester resin matrix show the same rate of degradation due to soil burial. (iii) The use of resin-rich face plies in a sandwich construction with fiberglass chopped strand mat (FCSM) as the core plies showed better resistance to the effects of soil burial than does an all-FCSM laminate.