The economic and technical advantages of particle filled polymer composites are a key reason in their increasing scientific and commercial importance over other engineering materials. The addition of particles to polymers has been proved to be an effective way to control their thermal, optical, and aesthetic properties. The scope of the current research is to assess the mechanical behaviour of particle reinforced solid surface composites made of alumina trihydrate filled poly (methylmethacrylate). A series of mechanical tests are performed including static fracture, flexural, and impact investigations. Microscopy studies are carried out to give an indication of the particle size and shape. The knowledge of the elastic modulus of particle filled polymers at different temperatures and filler contents is identified as a convenient way of categorising these materials. A concise methodology is developed for the measurement and prediction of the stiffness and fracture toughness of particle filled poly-methyl methacrylate.The experimental flexural modulus of the composites is found to decrease with increasing temperature (0 �°C - 90 DC) and increase with increasing particle volume fraction. Concurrent improvement of the stiffness and fracture toughness of the composites with increasing filler contents is indicated from the experimental results. The elastic behaviour of ATH-PMMA at different temperatures and filler volume fractions is fully evaluated by using a combination of experimental and theoretical modelling techniques. The Lielens, Lewis and Nielsen and the Constraint Composite (CCM) models are in excellent agreement with the experimental data. The complex deformation processes involved in the fracture of the composites are identified as the major factor associated with the difficulty in obtaining a complete understanding of the fracture behaviour of the materials. It is possible that the insight obtained through this work gives the possibility for future modelling of the fracture performance in future research.