8. (10 points) Now we have several square frames with a side length of 1 (the square frames cannot be taken apart), to form an $18 \times 15$ grid, at least $\qquad$ small square frames are needed.
【Solution】Solution: As shown in the figure, except for the first row, the last row, the leftmost column, and the rightmost column, the middle part can place one every other (gray cells can be left unfilled), according to the problem, forming an $18 \times 15$ grid. In the middle part, each row has $(18-2) \div 2=8$ cells that can be left unfilled, totaling $8 \times (15-2)=104$ cells that can be left unfilled. The minimum number of frames that need to be placed is $18 \times 15-104=166$. Therefore, the answer is 166.