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The tensile and impact properties of poly(l-lactic acid) composites filled with nanometer calcium carbonate (nano-CaCO3) were measured at room temperature. The results showed that the tensile elastic modulus increased roughly linearly while the tensile yield strength, tensile fracture strength and tensile elongation at break (δ b ) decreased nonlinearly with increasing the nano-CaCO3 weight fraction (W f ); when W f was constant, the δ b increased with increasing tensile rates. Both the V-notched Izod impact strength and V-notched Charpy impact strength showed the non-linear increase with increasing W f . The impact fracture surface was observed by means of a scanning electronic microscope to understand the toughening mechanisms.

The V-notched Izod impact strength of poly-L-lactide composites filled with nanosized calcium carbonate was measured at room temperature. The fractal dimensions of the impact fracture surface were determined by means of the structure function method, and the relationship between the measured impact strength and the fractal dimensions of the specimen fracture surface was investigated. The results showed that the fractal dimensions of the fracture surface were within the range of about 1.76 to 1.97, all of the correlation coefficients were higher than 0.9, the strong linear correlation indicated that the fractal characterization of the fracture surface for the composites was significant, the measured impact strength increased obviously with increasing fractal dimension of the fracture surface and the correlation between them was roughly linear when the fractal dimension was more than 1.88.

The effects of nanometer calcium carbonate content and tensile rate on the tensile properties of the filled polycaprolactone (PCL) composites were investigated. There was a certain reinforcing effect of the filler on the PCL resin. The tensile modulus increased nonlinearly, and the tensile strength also increased with increase of the filler weight fraction. When the filler weight fraction was kept constant, the tensile modulus and tensile strength increased slightly with increasing tensile rates. By comparing the experimental results with those determined from the tensile yield strength theory, the interfacial adhesion between the filler and matrix was found to be relatively strong; it should be one of the reasons for the good reinforcing effect.

The tensile properties of poly ( l -lactic acid) (PLLA) and polycaprolactone (PCL) composites filled with nanometer calcium carbonate (nano-CaCO3) were measured at room temperature and different tensile rates. With increase of the PCL weight fraction, the tensile elastic modulus, tensile strength and tensile strength at fracture for the PLLA/PCL/nano-CaCO3 composites decreased nonlinearly, and it increased slightly with increasing tensile rate. When the PCL weight fraction was less than 60%, the elongation at break for the composites increased slightly and then it increased sharply. This indicated that PCL was beneficial to improve the tensile fracture toughness of the composites.

The flexural properties of poly-L-lactide (PLLA) and polycaprolactone (PCL) shape memory composites filled with nanometer calcium carbonate (nano-CaCO3) were determined at room temperature. The results showed that with the increase of the nano-CaCO3 weight fraction the flexural moduli and strength of PCL/nano-CaCO3 composites increased roughly linearly and reached a maximum at the filler content of 2%, while the flexural strength of the composites decreased. The flexural moduli and strength of the composites decreased roughly linearly with increasing PLLA/PCL ratio for the PLLA/PCL/nano-CaCO3 composites.