Changing the font in latex

I am using latex to write a report. However, when I want to add a Gantt chart into it, I found that the font of all the content after this Gantt chart changed. So can anybody tell me how to get it back? Thanks! This is the code of the chapter includes Gantt chart

\section{Risk Analysis}

\section{Project Plan}
\definecolor{barblue}{RGB}{153,204,254}
\definecolor{groupblue}{RGB}{51,102,254}
\definecolor{linkred}{RGB}{165,0,33}
\renewcommand\sfdefault{phv}
\renewcommand\mddefault{mc}
\renewcommand\bfdefault{bc}
\setganttlinklabel{s-s}{START-TO-START}
\setganttlinklabel{f-s}{FINISH-TO-START}
\setganttlinklabel{f-f}{FINISH-TO-FINISH}
\sffamily
\begin{ganttchart}[
    canvas/.append style={fill=none, draw=black!5, line width=.75pt},
    hgrid style/.style={draw=black!5, line width=.75pt},
    vgrid={*1{draw=black!5, line width=.75pt}},
    title/.style={draw=none, fill=none},
    title label font=\bfseries\footnotesize,
    title label node/.append style={below=7pt},
    include title in canvas=false,
    bar label font=\mdseries\small\color{black!70},
    bar label node/.append style={left=2cm},
    bar/.append style={draw=none, fill=black!63},
    bar incomplete/.append style={fill=barblue},
    bar progress label font=\mdseries\footnotesize\color{black!70},
    group incomplete/.append style={fill=groupblue},
    group left shift=0,
    group right shift=0,
    group height=.5,
    group peaks tip position=0,
    group label node/.append style={left=.6cm},
    group progress label font=\bfseries\small,
    link/.style={-latex, line width=1.5pt, linkred},
    link label font=\scriptsize\bfseries,
    link label node/.append style={below left=-2pt and 0pt}
  ]{1}{14}
  \gantttitle[
    title label node/.append style={below left=7pt and -3pt}
  ]{WEEKS:\quad1}{1}
  \gantttitlelist{2,...,14}{1} \\
  \ganttgroup[progress=0]{WBS 1 More Research}{1}{1}\\
  \ganttgroup[progress=0]{WBS 2 Speaker Verification}{2}{3} \\
  \ganttgroup[progress=0]{WBS 3 StarGAN-VC}{4}{5} \\
  \ganttgroup[progress=0]{WBS 4 SV-StarGAN-VC}{6}{11} \\
  \ganttgroup[progress=0]{WBS 5 Document}{12}{14} \\
\end{ganttchart}
\section{Another Section if You Need It}
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa.

This the code of main.tex:

\documentclass[11pt,oneside]{book}
\usepackage[margin=1.2in]{geometry}
\usepackage{setspace}
\usepackage[toc,page]{appendix}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{pgfgantt}
\usepackage{float}
\usepackage[none]{hyphenat} % turn hyphenation off by default
\usepackage{graphicx}
\usepackage{hyperref}
\hypersetup{hypertex=true,
            colorlinks=true,
            linkcolor=blue,
            anchorcolor=blue,
            citecolor=blue}

\begin{document}

\frontmatter

\begin{titlepage}


\end{titlepage}


% -------------------------------------------------------------------
% Abstract
% -------------------------------------------------------------------

\input{chapters/abstract.tex}

% -------------------------------------------------------------------
% TOC etc
% -------------------------------------------------------------------

\tableofcontents
\listoffigures
\listoftables

\setstretch{1.1} 

\mainmatter

\input{chapters/Introduction.tex}
\input{chapters/Literature.tex}
\input{chapters/Analysis.tex}
\input{chapters/Planning.tex}
\input{chapters/Conclusions.tex}

\bibliographystyle{acm} 
\bibliography{mybibliography} 

\begin{appendices}
\input{chapters/appendixA.tex}
\input{chapters/appendixB.tex}
\end{appendices}

\end{document}

I know it is because I changed font when I am writing Gantt chart. But I just want to know how can I get the font of content after Gantt chart back?

Solution

You explicitly tell latex to change the font of the remaining document with \sffamily. If you want this to affect only the chart, use it inside a group or switch back to \rmfamily afterwards.

\documentclass[11pt,oneside]{book}
\usepackage[margin=1.2in]{geometry}
\usepackage{setspace}
\usepackage[toc,page]{appendix}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{pgfgantt}
\usepackage{float}
\usepackage[none]{hyphenat} % turn hyphenation off by default
\usepackage{graphicx}
\usepackage{hyperref}
\hypersetup{
%hypertex=true,
            colorlinks=true,
            linkcolor=blue,
            anchorcolor=blue,
            citecolor=blue}

\begin{document}

\section{Risk Analysis}

\section{Project Plan}
\definecolor{barblue}{RGB}{153,204,254}
\definecolor{groupblue}{RGB}{51,102,254}
\definecolor{linkred}{RGB}{165,0,33}
\renewcommand\sfdefault{phv}
\renewcommand\mddefault{mc}
\renewcommand\bfdefault{bc}
\setganttlinklabel{s-s}{START-TO-START}
\setganttlinklabel{f-s}{FINISH-TO-START}
\setganttlinklabel{f-f}{FINISH-TO-FINISH}
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. 
{
\sffamily
\begin{ganttchart}[
    canvas/.append style={fill=none, draw=black!5, line width=.75pt},
    hgrid style/.style={draw=black!5, line width=.75pt},
    vgrid={*1{draw=black!5, line width=.75pt}},
    title/.style={draw=none, fill=none},
    title label font=\bfseries\footnotesize,
    title label node/.append style={below=7pt},
    include title in canvas=false,
    bar label font=\mdseries\small\color{black!70},
    bar label node/.append style={left=2cm},
    bar/.append style={draw=none, fill=black!63},
    bar incomplete/.append style={fill=barblue},
    bar progress label font=\mdseries\footnotesize\color{black!70},
    group incomplete/.append style={fill=groupblue},
    group left shift=0,
    group right shift=0,
    group height=.5,
    group peaks tip position=0,
    group label node/.append style={left=.6cm},
    group progress label font=\bfseries\small,
    link/.style={-latex, line width=1.5pt, linkred},
    link label font=\scriptsize\bfseries,
    link label node/.append style={below left=-2pt and 0pt}
  ]{1}{14}
  \gantttitle[
    title label node/.append style={below left=7pt and -3pt}
  ]{WEEKS:\quad1}{1}
  \gantttitlelist{2,...,14}{1} \\
  \ganttgroup[progress=0]{WBS 1 More Research}{1}{1}\\
  \ganttgroup[progress=0]{WBS 2 Speaker Verification}{2}{3} \\
  \ganttgroup[progress=0]{WBS 3 StarGAN-VC}{4}{5} \\
  \ganttgroup[progress=0]{WBS 4 SV-StarGAN-VC}{6}{11} \\
  \ganttgroup[progress=0]{WBS 5 Document}{12}{14} \\
\end{ganttchart}
}
\section{Another Section if You Need It}
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. 

\end{document}