Mechanical Properties of Constructional PMMA at Elevated Temperatures and Postfire Conditions

Abstract

The application of Polymethylmethacrylate (PMMA) can be traced back decades ago, which is widely utilized in aerospace, submarine, aquarium, detector, and biomedicine, and now is gradually utilized in civil engineering structures such as large space structures and decorative structures. Due to the different processing methods and service conditions, whether the existing research is applicate to constructional PMMA remains to be explored. The fire resistance of PMMA is poor, and the mechanical properties decline sharply with increasing temperature. Additionally, the description of stress–strain curves is the foundation of engineering application for a material. Therefore, a series of mechanical property tests of constructional PMMA under a quasi-static state were carried out herein, investigating the stress–strain curves and hardness at elevated temperatures and postfire conditions. Scanning electron microscopy (SEM) images were utilized for fractographic analysis at elevated temperatures. The effects of different tensile rates, thicknesses, and adhesive joints were explored. The test results indicated that 80°C was a boundary temperature, because the elastic modulus, peak strength, and yield strength decreased slowly below 80°C and sharply over 80°C due to the softening of PMMA. When the temperature reached 80°C, the peak strength dropped to approximately half of that of room temperature, and the ductility of the specimen increased significantly. To promote the application of constructional PMMA and provide guidance for engineers, a material model from 20°C to 100°C, where the buildings often encountered, was proposed. The mechanical properties, especially the stress–strain curves, of constructional PMMA at elevated temperatures and postfire conditions were comprehensively analyzed, and design suggestions were given.