Your code has been messed up by copy-and-paste. This is my attempt at inserting multiplication signs * where they seemed to belong:
pAA = 0.5*(1 - l) + l;
pBB = 0.5*(l - 1) + 1;
pAB = 1 - pBB;
pBA = 1 - pAA;
bA = 0.99 x^2/(3 ((1 + (3.92*x^2)/9)^0.5 - 1));
bB = 3.2410^(-5) x^2/(3 ((1 + (4.210^(-9)*x^2)/9)^0.5 - 1));
D1 = (bA + bB)/2;
D2 = (bA - bB)/2;
alpha = 0.5 (bA + bB)/(bA*bB);
beta = 0.5 (bA - bB)/(bA*bB);
X = 0.25 beta*x;
l1 = 0.5 (pAA*Exp[-X] +
pBB*Exp[X] + ((pAA*Exp[-X] + pBB*Exp[X])^2 - 4 l)^0.5);
l2 = 0.5 (pAA*Exp[-X] +
pBB*Exp[X] - ((pAA*Exp[-X] + pBB*Exp[X])^2 - 4 l)^0.5);
C1 = 1 + (pAA*Exp[-X] - l1)^2/(pAB*pBA);
C2 = 1 + (pAA*Exp[-X] - l2)^2/(pAB*pBA);
phi1 = (pAA*Exp[-X] - l1)/(pAB*Exp[-X]);
phi1$ = (pAA*Exp[-X] - l1)/(pBA*Exp[X]);
phi2 = (pAA*Exp[-X] - l2)/(pAB*Exp[-X]);
phi2$ = (pAA*Exp[-X] - l2)/(pBA*Exp[X]);
shi1 = (pAA*Exp[-X] - l1)/(pAB*Exp[X]);
shi1$ = (pAA*Exp[-X] - l1)/(pBA*Exp[-X]);
shi2 = (pAA*Exp[-X] - l2)/(pAB*Exp[X]);
shi2$ = (pAA*Exp[-X] - l2)/(pBA*Exp[-X]);
EE = l1^49 (1/C1) (0.5 - 0.5 phi1$) (Exp[-X] - phi1*Exp[X]) +
l2^49 (1/C2) (0.5 - 0.5 phi2$) (Exp[-X] - phi2*Exp[X]);
k1 = (Exp[-X] (1 - phi1)) + (Exp[
X] ((-shi1*phi1) + (shi1*phi1*phi1$)));
k2 = (-Exp[-X]*
shi1$*(1 - phi1)) - (Exp[
X] ((-phi1*shi1*shi1$) + (phi1*phi1$*shi1*shi1$)));
k3 = (Exp[-X] (1 - phi1)) + (Exp[
X] ((-shi2*phi1) + (shi2*phi1*phi1$)));
k4 = (-Exp[-X]*
shi2$*(1 - phi1)) - (Exp[
X] ((-phi1*shi2*shi2$) + (phi1*phi1$*shi2*shi2$)));
k5 = (Exp[-X] (1 - phi2)) + (Exp[
X] ((-shi1*phi2) + (shi1*phi2*phi2$)));
k6 = (-Exp[-X]*
shi1$*(1 - phi2)) - (Exp[
X] ((-phi2*shi1*shi1$) + (phi2*phi2$*shi1*shi1$)));
k7 = (Exp[-X] (1 - phi2)) + (Exp[
X] ((-shi2*phi2) + (shi2*phi2*phi2$)));
k8 = (-Exp[-X]*
shi2$*(1 - phi2)) - (Exp[
X] ((-phi2*shi2*shi2$) + (phi2*phi2$*shi2*shi2$)));
T1 = 0.5 (((1/C1)^2) 50 (l1^(49)) (k1 +
k2) + ((1/C1) (1/C2) ((l1^50 - l2^50)/(l1 - l2)) (k3 +
k4) + ((1/C1) (1/C2) ((l2^50 - l1^50)/(l2 - l1)) (k5 +
k6)) + ((1/C2)^2) 50 (l2^49)*(k7 + k8)));
p1 = (((49 l1^49 - ((49 l1^49 - 49)*(l2/l1)^50))/(1 - (l2/l1))) - (l2/
l1)*((1 - (l2/l1)^49)/(1 - (l2/l1)^2)));
p2 = (((49 l2^49 - ((49 l2^49 - 49)*(l2/l1)^50))/(1 - (l2/l1))) - (l1/
l2)*((1 - (l1/l2)^49)/(1 - (l2/l1)^2)));
T2 = 0.5 ((((1/C1)^2) 1225 (l1^(49)) (k1 +
k2) + ((1/C1) (1/C2) p1 (k3 + k4) + ((1/C1) (1/C2)*
p2 (k5 + k6)) + ((1/C2)^2) 1225 (l2^(49)) (k7 + k8))));
p3 = (((49 l2^50 - ((49 l2^50 - 48)*(l1/l2)^49))/(1 - (l1/l2))) - (l1/
l2)*((1 - (l1/l2)^48)/(1 - (l1/l2)^2)));
p4 = (((49 l1^50 - ((49 l1^50 - 48)*(l2/l1)^49))/(1 - (l2/l1))) - (l2/
l1)*((1 - (l2/l1)^48)/(1 - (l2/l1)^2)));
T3 = 0.5 ((((1/C1)^2) 1225 (l1^(49)) (k1 +
k2) + ((1/C1) (1/C2) p3 (k3 + k4) + ((1/C2) (1/C1)*
p4 (k5 + k6)) + ((1/C2)^2) 1225 (l2^49) (k7 + k8))));
k9 = (k1*pAA*Exp[-X]) + (k2*pBA*Exp[-X]);
k10 = (-k1*pAB*Exp[X]) - (k2*pBB*Exp[X]);
k11 = (k3*pAA*Exp[-X]) + (k4*pBA*Exp[-X]);
k12 = (-k3*pAB*Exp[X]) - (k4*pBB*Exp[X]);
k13 = (k5*pAA*Exp[-X]) + (k6*pBA*Exp[-X]);
k14 = (-k5*pAB*Exp[X]) - (k6*pBB*Exp[X]);
k15 = (k7*pAA*Exp[-X]) + (k8*pBA*Exp[-X]);
k16 = (-k7*pAB*Exp[X]) - (k8*pBB*Exp[X]);
k17 = k9 - shi1*k10 - shi1$*k9 + shi1*shi1$*k10;
k18 = k9 - shi2*k10 - shi2$*k9 + shi2*shi2$*k10;
k19 = k11 - shi1*k12 - shi1$*k11 + shi1*shi1$*k12;
k20 = k11 - shi2*k12 - shi2$*k11 + shi2*shi2$*k12;
k21 = k13 - shi1*k14 - shi1$*k13 + shi1*shi1$*k14;
k22 = k13 - shi2*k14 - shi2$*k13 + shi2*shi2$*k14;
k23 = k15 - shi1*k16 - shi1$*k15 + shi1*shi1$*k16;
k24 = k15 - shi2*k16 - shi2$*k15 + shi2*shi2$*k16;
gec = 1225*l1^48;
ged = (((49 l1^48) - (49 l1^48 - 48)*(l2/l1)^49)/(1 - (l2/
l1))) - ((l2/l1)*(1 - (l2/l1)^48)/(1 - (l2/l1))^2);
gfc = (((49 l1^48) - (49 l1^48 - 48)*(l2/l1)^49)/(1 - (l2/
l1))) - ((l2/l1)*(1 - (l2/l1)^48)/(1 - (l2/l1))^2);
hec = (((49 l1^48) - (49 l1^48 - 48)*(l2/l1)^49)/(1 - (l2/
l1))) - ((l2/l1)*(1 - (l2/l1)^48)/(1 - (l2/l1))^2);
gfd = (((49 l2^48) - (49 l2^48 - 48)*(l1/l2)^49)/(1 - (l1/
l2))) - ((l1/l2)*(1 - (l1/l2)^48)/(1 - (l1/l2))^2);
hed = (((49 l2^48) - (49 l2^48 - 48)*(l1/l2)^49)/(1 - (l1/
l2))) - ((l1/l2)*(1 - (l1/l2)^48)/(1 - (l1/l2))^2);
hfc = (((49 l2^48) - (49 l2^48 - 48)*(l1/l2)^49)/(1 - (l1/
l2))) - ((l1/l2)*(1 - (l1/l2)^48)/(1 - (l1/l2))^2);
hfd = 1225*l2^48;
T4 = 0.5 (gec*k17 + ged*k18 + gfc*k19 + gfd*k20 + hec*k21 + hed*k22 +
hfc*k23 + hfd*k24);
Clear[f];
f[x_, l_] = ((1.550 alpha + 0.2550 x^2 (alpha^2 + beta^2) -
1.5 (1/EE) beta (1 + 0.33 alpha*x^2) T1 +
0.255049 alpha^2 x^2 - 0.5 (1/EE) x^2 (alpha*beta (T2 + T3)) +
beta^2*T4)^0.5)/50;
p = LogLinearPlot[f[x, 0.0], {x, 0.01, 10^8}, PlotRange -> All]
I have also redefined f with underscores and immediate assignment. However, the f that I got seems to have complex values, not real. The culprit may lie somewhere in those powers ^0.5
.