Geometry for unit cell

hello
please help
I am building a unit cell of nano fiber tube geometry. The unit cell is divided from matrix, interphase and nano tube as the attached picture 1. I have built a box w 2 cylinder. Is this code correct please ?
image
Pic 1

from dolfin import *
from mshr import *
import dolfin.common.plotting as fenicsplot
import numpy as np
from matplotlib import pyplot as plt

#Making a unit cell
interphase = Cylinder(Point(0, 0, -1), Point(0, 0, 1), 0.5, 0.5)
nano=Cylinder(Point(0, 0, -1), Point(0, 0, 1), 0.1, 0.1)
matrice = BoxMesh(Point(0, 0, 0),Point(1, 1, 1),8,8,8)
sphere=Sphere(Point(0, 0, -1) ,0.9)
matrice= Box(Point(0, 0, 0), Point(1, 1, 1))
geometry=nano + interphase +matrice

Making Mesh (40 corresponds to the mesh density)

mesh = generate_mesh(geometry, 40)